It can still freeze in the March vegetable garden.

Is it Going to Freeze Again in the March Vegetable Garden?

The first week of March is the average last day of frost but remain diligent and listen to the weather forecast. Soil temperatures and sneaky freezes will impact seed germination and plant viability.

Use a Soil Thermometer

Use a soil thermometer to determine the right time to plant

Since weather apps don’t tell you how warm the soil is, the best monitoring tool is a soil thermometer. If you are a home composter or baker, you may already have thermometers you can use. If your thermometer has a metal probe that will read at least 50°, you can use the tool on hand.

Test soil temperature where the seeds will be sprouting, so only push the probe in about 2-3 inches deep. The best time to test is mid-morning, around 10:00 or 11:00. After 4-5 days in a row of temperatures above 60° it is time to plant, and you can expect relatively quick and unhindered germination.

Monitoring soil temperature is important because our warm season vegetables – beans, cucumbers, squash, corn – germinate best when the soil temperature is above 60°. Okra, Southern peas, supersweet corn, and melons prefer it even warmer. Seeds sown in too cool soils may have spotty germination. Worse, if the soil is below 50°, seed will probably rot or emerge in a weakened state, causing them to be more susceptible to disease and pests.

Here is the checklist for Austin’s March Vegetable Gardens:

SITE SELECTION

• Choose planting beds or container locations that provide at least six to eight hours of full sun for optimum growth and production.

FERTILIZE

1. Apply fertilizer recommendations from your soil test.
2. Pull back mulch before applying fertilizer, water in well, then replace mulch to help protect from freeze.

WATER

• You may need to irrigate this month if rains don’t arrive.
• Strong spring winds can quickly desiccate young seedlings, so monitor water needs of new plantings.
• Transplants should be watered in their pots before transplanting and watered again after planting in the ground.
• Make sure to water transplants deeply when frost is in the forecast. Water helps protect the roots from cold.
• Avoid watering seeds from above, if possible, as this can cause the soil to crust, making it difficult for the seedlings to emerge.
• It’s especially important to keep water consistent in your onion patch. Onions will put on top growth more quickly as temperatures rise above 45°, and more top growth means larger onions once they start to bulb.

PLANT

Be sure to plant seeds at the proper depth. Check the seed packet.

• Start small if this is your first garden and remember that these lovely spring days are short-lived, with heat, insects, mosquitoes and water limitations to soon follow.
• Be sure to plant seeds at the proper depth. A good rule of thumb is to plant at a depth that is about 3 times the width of the seed. Consult the seed packet for more specific information.
• Always plant into moist soil. Water thoroughly the day before planting seed. Water again lightly after sowing to establish good soil-to-seed contact.
• Plant seeds of peas and greens early in the month, bush and pole beans, cucumbers, summer squash and winter squash later in the month.
• Plant flowers in and around the vegetable garden to attract beneficial insects.
• Hold off on melons, okra, sweet potatoes, and southern peas until the very end of the month or the first of April once the soil has warmed up to 65° F and the air temperature is between 70° and 85° F.

TRANSPLANT

• Tomato, eggplant and pepper transplants can go into the garden this month but be prepared to cover and protect them in the event of a late cold snap.
• If using tomato cages, wrap them individually with row cover.
• Eggplant and peppers will do better if you wait and put them out at the end of the month.
• Gradually expose all transplants to outdoor conditions before planting into the garden (even if you’ve bought them from a garden center.)
• Transplant herbs like oregano and thyme late in the month.

SOIL

• Work compost into the first few inches of the vegetable beds before you sow seeds or transplant vegetable starts.
• Mound soil, mulch or hay around potato plants so that only the top 2-3 inches of leafy growth is visible. It’s ok to bury the leaves and stem – that is where the tubers will develop.

DISEASES/PESTS TO LOOK FOR

• Aphids and caterpillars start to appear, and flea or harlequin beetles may be eating the cruciferous crops. Use blasts of water to control or investigate other less toxic solutions like insecticidal soap. Reference the Grow Green FAQ sheets for guidance.
• Monitor new seedlings for cutworms and wrap stems with a 2-inch strip of newspaper to prevent further damage. Aluminum foil or toilet paper rolls also may work.
• Destroy soil grubs as you find them.
• Use horticultural oil to spot treat for scale, taking care to completely coat the infestations. Do not spray oil on new leaves or blossoms.

HARVEST

• Continue harvesting cool season crops and monitor for pests; as temperatures rise the cool season crops become stressed and attract pests.

MAINTENANCE

Reconnect hoses and don’t forget to change the batteries in your irrigation timers.

• If your garden space is limited, now is a good time to harvest most of your cool-season vegetables to make room for warm season crops.
• Reconnect hoses and timers and check for leaks. Use soaker hoses or drip irrigation to direct water to the roots and avoid wetting the leaves.
• Weeding is critical, especially during the first 30-40 days of growth when plants are putting down roots.
• Use row cover to help protect from strong winds, insects and chilly nights.
• Pull up and compost cool season crops as soon as they start exhibiting stress.

Additional Resources

Watch the Vegetable Gardening in Central Texas Webinar

Vegetable Planting Calendar (English) (Español) (traditional Chinese)

Recommended Vegetable Varieties for Travis County

Vegetable Seed Sources

Vegetable Gardening in Austin

Plant Rotations, Successions and Intercropping

Rootknot Nematode Management

Monthly Gardening Calendar for Austin and Central Texas

About Sheryl Williams

Sheryl Williams has been a Travis County Master Gardener since 2010 and currently works as the Horticulture Program Assistant at Texas A&M AgriLife Extension – Travis County. She was introduced to gardening by her mom and grandma and has been an avid vegetable gardener most of her life. Sheryl believes that there is nothing more satisfying than growing and preparing your own food. She likes gardening in Austin year round and concedes that means pulling weeds every day. She practices organic gardening principles and enjoys the challenge of outsmarting garden pests. Occasionally she loses these battles, but doesn’t mind sharing a good meal.