Newsletter Archive

Humid weather encourages the spread of mildew and fungal infections. 

Powdery mildew appears as white coloration on leaves. Downy mildew can appear as spots on the top of leaves with grey coloring on the back. Downy mildew is prevalent later in the season and prefers cool, moist conditions.

Fungal diseases such as anthracnose, botrytis, and various blights and leaf spots become common after mid-summer. These can cause discoloration of foliage, dropping leaves, fruit loss, stunted growth, and plant death in severe cases. If you suspect a fungal disease, remove diseased leaves, and in severe cases the entire plant to slow spread of the disease. 

Some options to prevent mildew, fungal, and other diseases:

• Prune back your plants to increase air flow

• Water late in the day and try not to splash water on the leaves as this can spread disease

• Choose varieties that are mildew resistant

• Treat with copper fungicide

Copper fungicide can be mixed with water and applied with a spray bottle - preferably before any disease is spotted. Always read the label for proper application. Rain will wash off copper applications, so this can be less effective during wet periods.

When are green beans ready to harvest? Green beans are most tender when they have just reached their mature length, preferably before the shape of the beans inside is visible through the pod.  The beans will become tougher and stringy as they mature. This works for green beans, wax beans, and long beans. In the center photo above, the beans are a bit past their prime, while the long bean in the right photo is ready to pick. Expect to harvest beans daily or every other day.

If some beans are overripe, you can leave them on the vine until they fully mature and dry out, at which point you can collect the dried beans to plant next year.

Two common insect pests of green beans are bean aphids and Japanese beetles. Bean aphids can be washed off with a hose, or treated with insecticidal soap. It is best to purchase insecticidal soap concentrate or premixed soap rather than using dish soap.

Succession planting means planting additional new plants at regular intervals through the season. This allows for continual harvest, and also helps to avoid some pests. Plants with relatively short time to harvest work best. Good options are:

• basil 

• zucchini and summer squash

• bush beans

• lettuce

• greens

• kohlrabi

• beets

• turnips

• cilantro

• bunching onion

• cucumbers

• swiss chard

Now is a good time to start planning for fall. If you purchase seeds locally, you will want to look for cooler weather seeds now, before seeds are removed from displays in store. Online seed sales are available throughout the season, but some types of fall plantings, such as garlic, can be pre-ordered and sometimes sell out.

Some good options for fall planting are:

• marigolds

• greens

• garlic

• cabbage

• kohlrabi

• radish

• shallots

• turnips

• rutabagas*  (can be direct seeded in July for fall harvest)

Garlic needs to overwinter before harvest. Other types are planted in late summer for a fall or winter harvest. A hooped cover can sustain especially cold-hardy types through mid-winter. 

Japanese Beetles are active in July, and will feed on the leaves, flowers, and fruits of some types of plants. They particularly like grape, apple, raspberry, bean, basil, marigold, rose, and some other fruit trees. Damage looks like small holes in leaves, or a lace-like effect in heavy feeding. Large quantities of beetles can reduce crops of affected plants.

Leaves that have been fed on by beetles will attract more beetles, so you want to remove beetles as soon as you see them. Pick beetles off by hand or knock them into a container of soapy water. Beetles are slower in colder temperatures, so early morning or late evening are good times to remove them. Netting can keep beetles off of plants but also restricts pollinator access.

Beetle traps can attract more beetles to your garden and should be avoided. Neem oil can deter beetles somewhat. Bt developed for beetle control (there are multiple strains of Bt, check the label to be sure it is effective on beetles) can also provide some protection.

While vegetables that are in the ground usually have plenty of nutrients available, containers can be a different story. If you are growing in a soil medium that was not pre-fertilized, you may wish to add fertilizer to enhance growth. There are many options for fertilizers. 

Fertilizer labels have three numbers on them, which represent N - P - K, or nitrogen, phosphorous, and potassium, in that order. In the early season, the goal is usually to grow plants to a larger size quickly, in which case you want to select a fertilizer high in nitrogen. In mid season, when the plant is large and you want it to set fruit, switch to a fertilizer with less nitrogen and more phosphorus. If you apply a high nitrogen fertilizer, the plant can be suppressed from producing fruit.

Some options:

• Fish fertilizer is organic and high in nitrogen, the downside is that it smells like rotting fish for about a day after application

• Slow release granules are great, simple to apply, but can be more expensive

• Liquid fertilizers are easy to measure and apply, but often more expensive

• Granular fertilizer that needs to be mixed with water requires more care and labor in application but is less expensive 

ALWAYS READ THE LABEL. With fertilizer, more is not more, and you can damage your plants by adding too much fertilizer or the wrong kind of fertilizer. Err on the side of underfertilizing. Note that in some cases, you can cause problems with fruit (looking at you, tomatoes) with unbalanced fertilization. You will want to look into whether calcium is also needed as an additional additive for tomatoes, peppers, and eggplants, where insufficient calcium can result in blossom end rot.

If you are growing in the ground and not getting good results, you can send away for soil testing to find out if you have a nutrient imbalance of pH problem. This should be a first step before applying additives so you can be sure of exactly what you need to change.

Summer will come in with a vengeance during the week of June 23, with highs near 100F. This will cause any remaining cool season vegetables to bolt, such as lettuce, kale, and brassicas. Now is a good time to harvest these before the heat turns the plants bitter.

During hot spells, be sure to water any plants in containers daily, or more than once a day in some cases. It is best to water in the early morning or evening if possible. If you must water during the heat of the day, try not to splash water on the plant leaves, where it can cause damage under the hot sun.

Squash plants have male flowers and female flowers. Male flowers typically have long thin stems, while female flowers have "stems" that are the miniature fruit just starting to form. Squash plants first produce only male flowers, and then later begin to produce both male and female flowers. 

Squash flowers are edible for a summer treat. Pick male flowers early in the morning just after the open, then stuff with soft cheese or the filling of your choice, then lightly batter and saute in a pan.

Squash vine borers are a species of moth common to the area. The moths lay eggs on the stems of squash plants, and the caterpillars that emerge chew their way inside the stems of the squash. The caterpillars then eat the squash plant from inside, and are often noticed only once the entire plant suddenly wilts and dies within a matter of hours.

There can be two generations of borers during a summer. The first generation is due for eggs to hatch over the next few weeks. One way to kill the caterpillars is to treat the squash stems with a product such as Bt or spinosad either by spraying the outside of the stems thoroughly or by injecting the stems with a syringe. The main base of the stem is particularly vulnerable, as borers feeding at the base will kill the entire plant.

If you see evidence that borers have already entered the stem, but it has not yet wilted, you may still be able to save the plant. Borers can be carefully surgically removed by slitting open the stem along the length until you find the borer and remove it. Once the plant starts to wilt, it is usually not possible to save it.

Some squash types are less vulnerable to borers, such as varieties of Cucurbita moschata like cushaw. Squash that root along the stem, such as zucchini rampicante, can sometimes survive borer attacks.  Blue hubbard squash are a favorite of borers, and can be planted along the edge of the garden to act as a trap plant.

Last chance to plant! Garden stores are running low on transplants, and seeds should go into the ground asap.

It is still ok to plant the following:

beans (seeds or plants)

squash and melons (seeds or plants)

corn (seeds or plants)

chard (seeds or plants)

basil (plants)

June is the time to harvest garlic!

First, garlic scapes can be harvested when they emerge. These are the flower stalks that grow out of the center of the plant and start to form loops. You want to cut the scapes off once they have made a loop, and before they start to straighten back out. Once the scapes start to straighten, they become tough. Scapes can be used to make a garlic pesto, or added to stir fries.

After the scapes have been harvested, it will be a few weeks before the garlic bulbs are ready to harvest. The lower leaves on the garlic will start to dry out and turn brown. Once about 2/3 of the leaves are brown with green leaves only at the top, the garlic is ready to harvest. This could occur in June in warmer locations, or might take a bit longer in colder areas.

Use a garden fork or trowel to loosen the soil around the garlic when you are ready to harvest. Carefully dig out the garlic bulbs. The bulbs will need to be cured for storage - brush off any dirt, then put the garlic, still with stems, in a dark area for three or four weeks. Make sure the garlic has good ventilation. The bulbs can be hung or laid out on a screen. After curing the stems can be cut down.

Deer are year-round garden pests. If your plant suddenly disappears or sustains severe damage, deer are one of the likely culprits.

Some of their favorite vegetable plants are:

• sweet potato vines

• sunflowers

• peas

• beans

• broccoli

• cauliflower

• greens

• cabbage 

• beets

• carrots

However, deer will eat almost anything when they are hungry enough.

The best way to protect plants from deer is fencing or other barriers. In order to completely stop deer, you need a very tall fence - as high as 16 feet. One option is to use a homemade fence from T-posts strung with fishing line. The deer cannot see the fishing line and get confused about where the fence is, so they can have difficulty jumping over the fence. 

Another option for greens, root vegetables, or other shorter vegetables is to use insect netting or wire mesh fencing over hoops. Insect netting is inexpensive and also keeps out some insect pests such as cabbage white butterflies as well as squirrels and rabbits. Rebar and narrow pvc can be used to make quick and easy hoops that will last for years. The netting can be held in place with garden staples or pieces of lumber.

Deterrent sprays are available but tend not to be terribly effective.

Now is a good time to plant heat-loving plants, either from seed or transplants. 

Plants that can be started from seed in late May by direct sowing in the garden:

• beans

• chard

• corn

• squash 

• melons 

• cantaloupe 

• zucchini and summer squash 

• cucumbers

• sweet potato

• sunflower 

Summer lettuce can be planted now, try to choose a type that is tolerant of warm temperatures. Plant lettuce in a cooler spot and avoid direct afternoon sun if possible to reduce bolting.

When cold weather plants start to die off or bolt, pull them out and replace with summer plants.

"Trap crop" plants are used to draw pests away from your desirable vegetables and over to a plant that they like better.  Trap crops can be grown on the edges of your garden, or at the ends of rows.

Some plants commonly used as trap crops along with the insects they attract:

• blue hubbard squash - squash bugs, cucumber beetles, squash vine borer

• calendula - aphids

• nasturtiums - aphids

• sunflowers - stink bugs

• marigolds - nematodes for tomatoes

• dill - tomato hornworms

• amaranth - cucumber beetles

The Cabbage White butterfly can be seen fluttering around brassica plants such as kale, broccoli, and asian greens. These butterflies lay eggs on the back of the brassica leaves, which hatch into voracious caterpillars that are the same green color as the leaves. If the leaves on your brassica plants are full of holes, or disappear entirely, look for frass which indicates that caterpillars are lurking. Frass looks like little green pellets.

Cabbage white and other caterpillars can be controlled using organic sprays. Bt (bacillus thuringiensis) and spinosad are bacteria naturally found in soil that is toxic to caterpillars. These can be sprayed on the leaves so that when a caterpillar starts to eat a leaf, it is quickly poisoned, stops eating, and then dies. These sprays are not harmful to humans or pets (aside from insect pets), and can be found at hardware stores and nurseries. Follow the instructions on the label when applying.  These pesticides break down quickly in sunlight and are washed off by rain, so do not apply during a rainy period.

Most warm season plants can go outside now, especially if you are in a warmer area (in the city or on the Bay) or are growing in containers with a southern exposure. If your local area is on the colder side (upper Montgomery, Frederick), hold off until after May 13, at which point nighttime temperatures should be warmer.

The main plants to be concerned with are basil and sweet potato, all other warm season plants should be ready to go after hardening off.

For plants that you have started inside from seed, you will need to harden these off in a protected location outdoors preferably for at least a week or two before planting in the ground. Start with a shaded area if possible and slowly acclimate the plants to receive more and more sun. Tomatoes can be hardened off but should be brought inside if night temperatures get too cold (40s or low 50s). Basil is even more cold sensitive than tomatoes.

Go ahead and plant:

broccoli and cauliflower

cabbages 

carrots and beets (seeds or seedlings)

lettuce and other greens

all herbs - parsley, cilantro, dill, rosemary, lavendar

cane fruit

rhubarb (from rhizomes)

tomatoes

tomatillos

summer and winter squash

beans

melons

cucumbers

WAIT another week to plant in colder areas:

basil

sweet potato

Plant supports are helpful for many vegetables, especially vining plants and those with heavy fruits. There are many options for supports to choose from:

• Stakes, sticks, and poles - metal, bamboo, or wood, these are best for plants that just need a little support. Longer, heavier poles can be used to make tripods for beans

• Cages - these are available premade at hardware stores, or you can make your own from heavy wire mesh (this is a fairly intensive project and requires a truck for purchase of mesh if you are making larger cages). A frequent mistake is to underestimate the size of the cage needed, especially for tomatoes. Indeterminate tomatoes need larger, taller cages. Compact determinate tomatoes, some tomatillos, and other bushy plants like some peppers can benefit from medium or smaller cages. Peas and beans can also be grown around the circumference of tall cages.

• Trellis - premade wood, plastic, or metal trellises are available at stores. These can be used for beans, peas, some squash, and vining flowers

• Netting - string netting (or garden netting) with several inch openings can be used for many climbing or vining plants, including tomatoes, beans, and squash.  A sturdy structure is needed to provide support for the netting. Do not use bird netting, as it has a tendency to trap and kill birds, snakes, and small animals

• Rope or heavy twine - Instead of netting, some vining plants can be trained to climb up a heavy string or rope. 

Some warm season plants can go outside now, especially if you are in a warmer area (in the city or on the Bay) or are growing in containers with a southern exposure. If your local area is on the colder side (upper Montgomery, Frederick), hold off another week on planting. 

The less hardy summer plants need to wait until mid to late May before planting.

For plants that you have started inside from seed, you will need to harden these off in a protected location outdoors preferably for at least a week or two before planting in the ground. Start with a shaded area if possible and slowly acclimate the plants to receive more and more sun. Tomatoes can be hardened off but should be brought inside if night temperatures get too cold (40s or low 50s). Basil is even more cold sensitive than tomatoes.

Go ahead and plant:

broccoli and cauliflower

cabbages 

carrots and beets (seeds or seedlings)

lettuce and other greens

hardy herbs - parsley, cilantro, dill, rosemary, lavendar

cane fruit

rhubarb (from rhizomes)

Plant only if you are in a warm location:

tomatoes

tomatillos

summer and winter squash

beans

melons

cucumbers

WAIT to plant:

basil

sweet potato

Seedlings that have been started indoors need to spend some time outdoors to acclimate, or 'harden off' before planting. As the days grow warmer, seedlings can be set outside in their pots in a sheltered area - at first keep them in partial or full shade. Once they have spent at least a few days if not a week or so in shade, they can be moved into a sunnier location. Bring them inside at night if it is too cold, especially for peppers, tomatoes, eggplant, and basil. 

Be sure to water seedlings regularly and monitor their condition, as they will dry out much faster outdoors than inside. 

Plants in the nightshade family have the ability to easily grow roots from anywhere along the main stem. You should use this to your advantage when planting. This is especially helpful if your seedlings are a bit leggy.

First, pick off any lower leaves on the plant, keeping just the leaves near the top. Dig out a shallow trough for planting. Lay the seedling down on its side, and cover both the roots and most of the main stem with soil, leaving only the top few inches and leaves above the soil. The plant will grow roots out along the whole stem, and you will have a plant with a strong base.

Squash and melon vines are often best started from seed, as they do not like to be transplanted. It is often recommended to plant the seeds in a mound of soil, which improves drainage for the plants and warms up faster than the surrounding level ground. The vines take up a lot of space in the garden, so you want to be sure to space out the mounts without crowding the plants. Check the seed packet to determine spacing - some summer squash types tend to be more compact and bushy, while winter squash and melons are rambling vines. For vining types, you can optionally use a trellis or other support to train the vine to grow vertically if desired.

Form a mound that is roughly 2 feet across and 6-8" tall. It is nice to use composted materials to help form your mounds. On the top of the mound, plant 2-3 seeds a few inches apart, and water the mound. The seeds should germinate within a week or two if temperatures are warm enough. You can pinch off the weaker seedlings leaving one seedling per mound. 

If you have purchased seedlings, be very gentle in handling the roots when planting. Try to avoid disturbing the roots as much as possible.

Flowers play an important role in the vegetable garden, attracting both pollinator insects and beneficial insects that will attack garden pests. Interspersing a variety of flowers with your vegetables will help to keep your plants healthy and productive. 

Some flowers are more useful than others in attracting pollinators. Be wary of flowers that have extra petals or unusual flower shapes, as these may have been specially bred to attract humans but are not as interesting for insects. You can also allow herbs to flower, such as fennel, dill, and cilantro.

Good flowers for the garden:

mountain mint

monarda (bee balm)

zinnia

sunflower

cosmos

coneflower

milkweed

goldenrod

blanket flower (gaillardia)

salvia

agastache

Cool weather plants should be started soon in order for plants to mature before it gets too hot. Lettuce and kale become bitter once temperatures warm in May, and the plants may "bolt" or start to flower. Swiss chard is more tolerant of hot weather and can be planted any time from late March through the end of May. The time to plant peas and radish outside has passed.

One option to speed growth is to start plants from seed indoors and then plant the seedlings outside as soon as they are large enough to handle without damage. If you are in a colder area, using a row cover to protect young lettuce can help in early April.

Lettuce seeds need light and moisture to germinate. Rough up the soil a little bit before planting the seeds, but do not bury the seeds under the soil. 

Carrots need loose soil in order to grow long roots, otherwise they will be stunted if you have hard packed soil. If you are growing carrots in a container, pick a loose soil mix such as potting mix. Carrots will bolt in warm weather, so they should be planted in late March or April.

Onion sets - small bulbs - can be purchased at feed and hardware stores and some nurseries and are easier to grow than starting onion from seeds. 

It is now warm enough to direct seed some herb types outdoors, or start the seeds indoors and move outside. This includes dill, cilantro, and parsley.

Seedlings that have been started indoors need to spend some time outdoors to acclimate, or 'harden off' before planting. As the days grow warmer, seedlings can be set outside in their pots in a sheltered area - at first keep them in partial or full shade. Once they have spent at least a few days if not a week or so in shade, they can be moved into a sunnier location. Bring them inside at night if it is too cold, especially for peppers, tomatoes, eggplant, and basil. 

Be sure to water seedlings regularly and monitor their condition, as they will dry out much faster outdoors than inside. 

Potatoes can be planted in late March through mid-April. While you can try to use supermarket potatoes, seed potatoes specially intended for growing potato plants are better because they are usually guaranteed to be free of disease, while potatoes from the grocery store may carry diseases that can infect your soil and cause problems. Seed potatoes can be found at feed stores (Tractor Supply, Southern States) and at some hardware stores and nurseries.

Each seed potato can be cut into pieces to grow multiple potato plants, or used whole if you prefer. Cut the potato so that each section has at least 1-2 'eyes' - the eye will sprout to form the new plant. Cutting the potato will increase the chance of rotting or disease, so after cutting, let the sections sit in a well-ventilated area that is not in direct sun for a few days until the cut sides dry out.

Potatoes can be planted in garden beds, or are sometimes grown in grow bags for easier harvest. 

Unlike potatoes, sweet potatoes are sprouted first, and only the sprouts are planted rather than pieces of the tuber. If you want to sprout your own sweet potato, you can start with a store-bought tuber. Organic sweet potatoes are less likely to be treated with anti-sprouting agents. There are several ways to sprout your sweet potato, including using toothpicks to partially submerge the tuber in a glass or bowl of water, or sprouting in soil. Here is one website with good instructions on using a small tray of soil:

https://piedmontmastergardeners.org/article/how-to-grow-your-own-sweet-potato-slips/

The sprouts, called slips, are gently twisted off of the tuber and can be planted directly in the ground, rooted in water, or potted up to grow inside before planting. Sweet potatoes are more sensitive to temperature than regular potatoes and should not be planted outside until after Mother's Day.

Sweet potato vines like to ramble and can take up a bit of space. The vines are rather attractive and have nice flowers. Note that deer really like to eat the sweet potato vines. Sweet potatoes can be planted in garden beds, or are sometimes grown in grow bags to make it easier to harvest. 

Common chickweed, Stellaria media, likes cool weather and moist conditions. This non-native weed grows quickly as a low mound, and has small white flowers. Common chickweed is edible both raw and cooked. It does not like hot, dry conditions, and will die back in summer to return again as temperatures cool in the fall.

Early April is a good time to start tomatoes, tomatillos, and basil from seed. 

Tomatoes are grouped into two main types: determinate (bushy) and indeterminate (vining). Bushy types are better suited for containers, especially the compact and dwarf varieties. Most determinate tomatoes will do well with a basic tomato cage for stability. Indeterminate tomatoes will absolutely need a trellis or large cage. Cherry and plum types tend to be easier for beginners. Types with larger fruits can be more prone to blossom end rot, diseases, and other problems. Deer will eat tomato plants - both fruits and leaves - so plan ahead for how you will protect your plants if you are in a deer-prone area.

Tomato seeds enjoy warmth for germination. Some options are to initially put the pots on top of the refrigerator or in the oven with just the oven light on until the seeds start to germinate, then move them to a well-lit location. Seed warming mats are also available online at specialty vendors.  Tomatoes should not be started in tiny pots as they will outgrow the pot quickly, so start tomatoes in pots that are several inches deep and wide. You will need a lot of light to keep tomato seedlings happy. 

Tomatillos are somewhat similar to tomatoes, but less well suited to containers. You must have at least two tomatillo plants, as each plant needs to be pollinated by a different plant in order to produce fruits. Tomatillos are bushy but can get quite large, so will need caging. Tomatillo seeds should be treated similar to tomato seeds. 

Basil is extremely easy to grow from seed. If you don't want to use seeds, you can also take a cutting from a basil plant and stick it in a cup of water to grow roots, then it can be potted up once there are enough roots. Basil seeds can be started in small pots or a tray, with several seeds to a pot that are divided later on.  A type of basil that does well here is the "Prospera" series which is a non-GMO collection of basil types bred to be resistant to downy mildew and fusarium wilt. Prospera types are most easily found at online seed vendors.

Tip: In the DC area, the safe outdoor planting date for after last frost is generally considered to be Mother's Day weekend. If you want to start the seeds indoors and then plant the seedling outdoors, the packet will indicate how many weeks in advance the seeds need to be started. 

Tip: To avoid fungus gnats, add in a small amount of Mosquito Bits (available at hardware stores or online) to your soil mix. These release a type of bacteria that kills mosquito and gnat larvae, and are safe for humans and pets.

Tip: Expensive "grow lights" are not necessary. A simple led or fluorescent shop light with a timer will work just fine, but you want to get the light just a few inches above the seedlings, and have a way to adjust the height of the lamps as the seedlings grow. If your light gives off a lot of heat, it might fry or singe the seedlings if it gets too close. If your seedlings are leggy - tall and thin - they do not have enough light. Either add more lights or move the light closer to the seedlings.

Cool weather plants should be started soon in order for plants to mature before it gets too hot. Lettuce and kale become bitter once temperatures warm in May, and the plants may "bolt" or start to flower. Swiss chard is more tolerant of hot weather and can be planted any time from late March through the end of May. The time to plant peas and radish outside has passed.

One option to speed growth is to start plants from seed indoors and then plant the seedlings outside as soon as they are large enough to handle without damage. If you are in a colder area, using a row cover to protect young lettuce can help in early April.

Lettuce seeds need light and moisture to germinate. Rough up the soil a little bit before planting the seeds, but do not bury the seeds under the soil. 

Carrots need loose soil in order to grow long roots, otherwise they will be stunted if you have hard packed soil. If you are growing carrots in a container, pick a loose soil mix such as potting mix. Carrots will bolt in warm weather, so they should be planted in late March or April.

Onion sets - small bulbs - can be purchased at feed and hardware stores and some nurseries and are easier to grow than starting onion from seeds. 

It is now warm enough to direct seed some herb types outdoors, or start the seeds indoors and move outside. This includes dill, cilantro, and parsley.

Potatoes can be planted in late March through mid-April. While you can try to use supermarket potatoes, seed potatoes specially intended for growing potato plants are better because they are usually guaranteed to be free of disease, while potatoes from the grocery store may carry diseases that can infect your soil and cause problems. Seed potatoes can be found at feed stores (Tractor Supply, Southern States) and at some hardware stores and nurseries.

Each seed potato can be cut into pieces to grow multiple potato plants, or used whole if you prefer. Cut the potato so that each section has at least 1-2 'eyes' - the eye will sprout to form the new plant. Cutting the potato will increase the chance of rotting or disease, so after cutting, let the sections sit in a well-ventilated area that is not in direct sun for a few days until the cut sides dry out.

Potatoes can be planted in garden beds, or are sometimes grown in grow bags for easier harvest. 

Unlike potatoes, sweet potatoes are sprouted first, and only the sprouts are planted rather than pieces of the tuber. If you want to sprout your own sweet potato, you can start with a store-bought tuber. Organic sweet potatoes are less likely to be treated with anti-sprouting agents. There are several ways to sprout your sweet potato, including using toothpicks to partially submerge the tuber in a glass or bowl of water, or sprouting in soil. Here is one website with good instructions on using a small tray of soil:

https://piedmontmastergardeners.org/article/how-to-grow-your-own-sweet-potato-slips/

The sprouts, called slips, are gently twisted off of the tuber and can be planted directly in the ground, rooted in water, or potted up to grow inside before planting. Sweet potatoes are more sensitive to temperature than regular potatoes and should not be planted outside until after Mother's Day.

Sweet potato vines like to ramble and can take up a bit of space. The vines are rather attractive and have nice flowers. Note that deer really like to eat the sweet potato vines. Sweet potatoes can be planted in garden beds, or are sometimes grown in grow bags to make it easier to harvest. 

One of the first weeds to emerge in spring is hairy bittercress, Cardamine hirsuta. Bittercress overwinters as a small whorl of leaves a few inches across, then puts out small white flowers on thin stems starting in late March. While bittercress can be somewhat endearing at this stage, the flowers quickly go to seed. Once bittercress forms seeds, a light touch will cause the seeds to shoot in all directions as far as 16 feet! Pull bittercress as soon as you see it in spring, before it can set seeds.

Hairy bittercress is edible with a peppery flavor and can be used raw in salads if it has not been treated with chemicals or exposed to other contaminants.

Late March is a good time to start tomatoes, tomatillos, and basil from seed. If you are short on space and don't plan to move your plants outdoors until late May, you can wait until April.

Tomatoes are grouped into two main types: determinate (bushy) and indeterminate (vining). Bushy types are better suited for containers, especially the compact and dwarf varieties. Most determinate tomatoes will do well with a basic tomato cage for stability. Indeterminate tomatoes will absolutely need a trellis or large cage. Cherry and plum types tend to be easier for beginners. Types with larger fruits can be more prone to blossom end rot, diseases, and other problems. Deer will eat tomato plants - both fruits and leaves - so plan ahead for how you will protect your plants if you are in a deer-prone area.

Tomato seeds enjoy warmth for germination. Some options are to initially put the pots on top of the refrigerator or in the oven with just the oven light on until the seeds start to germinate, then move them to a well-lit location. Seed warming mats are also available online at specialty vendors.  Tomatoes should not be started in tiny pots as they will outgrow the pot quickly, so start tomatoes in pots that are several inches deep and wide. You will need a lot of light to keep tomato seedlings happy. 

Tomatillos are somewhat similar to tomatoes, but less well suited to containers. You must have at least two tomatillo plants, as each plant needs to be pollinated by a different plant in order to produce fruits. Tomatillos are bushy but can get quite large, so will need caging. Tomatillo seeds should be treated similar to tomato seeds. 

Basil is extremely easy to grow from seed. If you don't want to use seeds, you can also take a cutting from a basil plant and stick it in a cup of water to grow roots, then it can be potted up once there are enough roots. Basil seeds can be started in small pots or a tray, with several seeds to a pot that are divided later on. 

This is also the time to start broccoli indoors. Note that broccoli uses up a lot of real estate in the garden, does not always form broccoli heads, and is a favorite snack of some insect types. For alternatives, consider some Asian brassicas such as gai lan, which should be harvested young for the tender stems.

Tip: In the DC area, the safe outdoor planting date for after last frost is generally considered to be Mother's Day weekend. If you want to start the seeds indoors and then plant the seedling outdoors, the packet will indicate how many weeks in advance the seeds need to be started. 

Tip: To avoid fungus gnats, add in a small amount of Mosquito Bits (available at hardware stores or online) to your soil mix. These release a type of bacteria that kills mosquito and gnat larvae, and are safe for humans and pets.

Tip: Expensive "grow lights" are not necessary. A simple led or fluorescent shop light with a timer will work just fine, but you want to get the light just a few inches above the seedlings, and have a way to adjust the height of the lamps as the seedlings grow. If your light gives off a lot of heat, it might fry or singe the seedlings if it gets too close. If your seedlings are leggy - tall and thin - they do not have enough light. Either add more lights or move the light closer to the seedlings.

Cool weather plants should be started in March in order for plants to mature before it gets too hot. Lettuce and kale become bitter once temperatures warm in May, and the plants may "bolt" or start to flower. Swiss chard is more tolerant of hot weather and can be planted any time from late March through the end of May.

One option to speed growth is to start plants from seed indoors and then plant the seedlings outside as soon as they are large enough to handle without damage. Some types that are very cold tolerant can be planted unprotected in March, but many types prefer some protection from freezing temperatures such as a cold frame or row cover. If you do not have a cover, you may want to wait until the end of March to direct sow seeds outside. 

Lettuce seeds need light and moisture to germinate. Rough up the soil a little bit before planting the seeds, but do not bury the seeds under the soil. 

Carrots need loose soil in order to grow long roots, otherwise they will be stunted if you have hard packed soil. If you are growing carrots in a container, pick a loose soil mix such as potting mix. Carrots will bolt in warm weather, so they should be planted in late March or April.

Potatoes can be planted in late March through mid-April. While you can try to use supermarket potatoes, seed potatoes specially intended for growing potato plants are better because they are usually guaranteed to be free of disease, while potatoes from the grocery store may carry diseases that can infect your soil and cause problems. Seed potatoes can be found at feed stores (Tractor Supply, Southern States) and at some hardware stores and nurseries.

Each seed potato can be cut into pieces to grow multiple potato plants, or used whole if you prefer. Cut the potato so that each section has at least 1-2 'eyes' - the eye will sprout to form the new plant. Cutting the potato will increase the chance of rotting or disease, so after cutting, let the sections sit in a well-ventilated area that is not in direct sun for a few days until the cut sides dry out.

Potatoes can be planted in garden beds, or are sometimes grown in grow bags for easier harvest. 

Unlike potatoes, sweet potatoes are sprouted first, and only the sprouts are planted rather than pieces of the tuber. If you want to sprout your own sweet potato, you can start with a store-bought tuber. Organic sweet potatoes are less likely to be treated with anti-sprouting agents. There are several ways to sprout your sweet potato, including using toothpicks to partially submerge the tuber in a glass or bowl of water, or sprouting in soil. Here is one website with good instructions on using a small tray of soil:

https://piedmontmastergardeners.org/article/how-to-grow-your-own-sweet-potato-slips/

The sprouts, called slips, are gently twisted off of the tuber and can be planted directly in the ground, rooted in water, or potted up to grow inside before planting. Sweet potatoes are more sensitive to temperature than regular potatoes and should not be planted outside until after Mother's Day.

Sweet potato vines like to ramble and can take up a bit of space. The vines are rather attractive and have nice flowers. Note that deer really like to eat the sweet potato vines. Sweet potatoes can be planted in garden beds, or are sometimes grown in grow bags to make it easier to harvest. 

Basil:

A type of basil that does well here is the "Prospera" series which is a non-GMO collection of basil types bred to be resistant to downy mildew and fusarium wilt. Prospera types are most easily found at online seed vendors.

Cilantro:

Cilantro is easily grown from seed. For continuous harvest, plant a new batch of seeds every two weeks. When temperatures increase in summer, cilantro will tend to bolt and produce flower stalks. If you want to collect coriander (cilantro seeds), you can let the flowers mature to produce seeds. However if you only want fresh cilantro leaves, the cilantro should be pulled once it starts to bolt. Some varieties of cilantro are less prone to bolting, which is usually indicated on the seed packet as "slow bolt".

Squash:

A big problem for growing summer and winter squash is squash borer larvae that quickly kill entire squash plants in mid summer. Some types of squash are less prone to severe damage from borers:

Zucchini rampicante (or Tromboncino)- can be used as zucchini when immature, or left to mature for winter squash. The vine grows roots along the length of the vine, so portions of the plant can survive when attacked by borers. The large squash are long and skinny and the vine likes to ramble.

Moschata squash types have a stem that is resistant to borers:

• Tatuma/Tatume squash 

• Butternut  

• Cushaw 

• Futtsu

• Zephyr

Flowers:

In addition to vegetables, consider planting some flowers around your garden. Flowers will attract predator insects who will attack vegetable pests such as aphids and hornworms. Some flower seed mixes are specially selected to attract these beneficial insects.

Some vegetable varieties good for containers:

"Patio Choice" tomato - available in red or yellow types - early production that lasts until a freeze

"Pot-a-peno" jalapeno type is highly productive and works great in a small container

Start shelling and snow peas by mid-March. Peas can be quickly germinated indoors layered between wet paper towels. Either cover with plastic or place in an enclosed area such as a microwave, checking at least once daily until the roots start to emerge from the seeds. Germinated peas can then be planted directly outdoors in a prepared bed, being careful not to damage the emergent roots. Most peas need a trellis, net, or other structure to climb for support.  Peas can also be planted without pre-germinating, but may be slow to germinate with cold outdoor temperatures.

Peas can be tricky in this area, as they do not tolerate hot weather, and a warm May can limit harvests. Look for pea varieties with a shorter time to maturity or advertised as "heat tolerant".

Sweet and hot peppers and eggplants should be started by mid-March in order to be ready to plant outside in early/mid May. These seeds need warmth to germinate so be sure they are in a warm location.  Some options are to initially put the pots on top of the refrigerator or in the oven with just the oven light on until the seeds start to germinate, then move them to a well-lit location. Seed warming mats are also available online at specialty vendors.

Tomatoes tend to be a little faster growing. Tomatoes should not be started in tiny pots as they will outgrow the pot quickly, so start tomatoes in pots that are several inches deep and wide. They also appreciate heat for germination. If you don't have a lot of room indoors, wait until the end of March to start your tomatoes or you will be dealing with a jungle of plants in late April. 

Tip: In the DC area, the safe outdoor planting date for after last frost is generally considered to be Mother's Day weekend. If you want to start the seeds indoors and then plant the seedling outdoors, the packet will indicate how many weeks in advance the seeds need to be started. 

Tip: To avoid fungus gnats, add in a small amount of Mosquito Bits (available at hardware stores or online) to your soil mix. These release a type of bacteria that kills mosquito and gnat larvae, and are safe for humans and pets.

Tip: Expensive "grow lights" are not necessary. A simple led or fluorescent shop light with a timer will work just fine, but you want to get the light just a few inches above the seedlings, and have a way to adjust the height of the lamps as the seedlings grow. If your light gives off a lot of heat, it might fry or singe the seedlings if it gets too close. If your seedlings are leggy - tall and thin - they do not have enough light. Either add more lights or move the light closer to the seedlings.

Cool weather plants should be started in March in order for plants to mature before it gets too hot. Lettuce and kale become bitter once temperatures warm in May, and the plants may "bolt" or start to flower. 

One option to speed growth is to start plants from seed indoors and then plant the seedlings outside as soon as they are large enough to handle without damage. Some types that are very cold tolerant can be planted unprotected in March, but many types prefer some protection from freezing temperatures such as a cold frame or row cover. If you do not have a cover, you may want to wait until the second half of March to direct sow seeds outside. 

Lettuce seeds need light and moisture to germinate. Rough up the soil a little bit before planting the seeds, but do not bury the seeds under the soil. 

Tip for Raised Beds: A new product available at hardware stores are "planter wall blocks" - concrete bricks with notches to insert boards. These blocks can be stacked to make tall beds. Newer pressure treated lumber does not contain arsenic and is safer than older pressure treated boards. Cedar or redwood boards will last longer than soft pine but cost much more. Even untreated cheap pine boards should last several years before needing replacement.

Tip: Some newer build housing (post ~2000) has extremely low quality "fill" that consists largely of rocks and chunks of construction debris. If you can barely get a trowel into the ground without hitting rocks and debris, strongly consider using raised beds or containers rather than trying to work with the existing "soil".

Tip for Soil: One way to improve the quality of your soil is to add a few inches of good quality composted material on top of the existing soil. Bags of additives such as cow manure, LeafGro, municipal compost, or better quality "topsoil" mixes can be used.  LeafGro is a great local product in the DC area produced in Montgomery County that currently costs around $6 for 1.5 cubic feet, but is also available by the truckload from bulk suppliers. Avoid if possible the super cheap bagged "topsoil" sold at many big box stores as the quality is very low and your plants will likely struggle. If using manure from a local farm, use caution with manure that has a high straw content. Some sources of straw treat their straw with broadleaf herbicides that can damage vegetable plants.

Seeds are now for sale at local stores and online.  Seed potatoes and onion sets will start appearing in stores soon as well. Commercial seed companies should have rigorous quality controls to ensure that seeds are viable and that the correct seeds are in the seed packets. Quality amongst independent vendors (ebay, etsy) is variable. Local garden clubs may also have seed exchanges.