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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.