Illinois’ March brings a race against time to plant vegetables that mature before summer heat or fall frost. Choosing the best vegetables to plant in march in illinois means focusing on cold-hardy crops that can handle late snow and early thaws. You want varieties that germinate in cool soil and produce quickly before the oppressive humidity of July arrives.
This guide covers everything you need for a successful March planting in Illinois. We will look at soil prep, timing, and specific vegetable picks for both northern and southern zones. By following these steps, you can enjoy fresh produce as early as May.
Understanding Illinois Climate Zones For March Planting
Illinois spans USDA hardiness zones 5a in the north to 7a in the south. March temperatures vary widely across the state. Northern Illinois often sees frost until mid-April, while southern areas can start planting two weeks earlier.
Check your local frost date before putting seeds in the ground. For most of Illinois, the last spring frost occurs between April 10 and April 30. March planting is best for crops that tolerate light frost or can be started indoors.
Soil Temperature Requirements
Most cool-season vegetables need soil temperatures between 40°F and 75°F to germinate. Use a soil thermometer to check at 2 inches deep. If the soil is below 40°F, seeds may rot or germinate slowly.
Warm the soil by covering beds with black plastic or row covers for a week before planting. This simple step can raise soil temperature by 5 to 10 degrees.
Best Vegetables To Plant In March In Illinois
Here are the top choices for March planting. These vegetables thrive in cool weather and can handle occasional frost. They also mature quickly, giving you a harvest before summer heat sets in.
Peas
Peas are a classic March crop in Illinois. Sow seeds directly into the ground as soon as the soil can be worked. Sugar snap peas and snow peas are especially productive.
Plant peas 1 inch deep and 2 inches apart in rows. They need support like trellises or netting. Harvest in 60 to 70 days. Peas stop producing once temperatures hit 80°F.
Spinach
Spinach loves cool weather and can survive light frosts. Sow seeds 1/2 inch deep in rich soil. Thin seedlings to 6 inches apart for larger leaves.
Choose varieties like ‘Bloomsdale’ or ‘Tyee’ for better bolt resistance. Harvest outer leaves starting at 40 days. Spinach bolts quickly in heat, so plant in early March for best results.
Lettuce
Lettuce is another fast-growing cool-season crop. Plant leaf lettuce varieties for continuous harvest. Romaine and butterhead also work well in March.
Sow seeds 1/4 inch deep and keep soil moist. Thin to 8 inches apart. Use row covers to protect from hard frosts. Harvest in 45 to 55 days.
Kale
Kale is extremely cold-hardy and can survive temperatures down to 20°F. Plant seeds 1/2 inch deep in well-drained soil. Space plants 12 inches apart.
Kale improves in flavor after a frost. Harvest outer leaves as needed. Varieties like ‘Lacinato’ and ‘Red Russian’ are popular for Illinois gardens.
Carrots
Carrots need loose, sandy soil free of rocks. Sow seeds 1/4 inch deep in rows 12 inches apart. Keep soil consistently moist for good germination.
Choose short or round varieties like ‘Paris Market’ for heavier clay soils. Carrots take 60 to 80 days to mature. They can be left in the ground until frost.
Radishes
Radishes are the fastest vegetable to grow from seed. Plant them 1/2 inch deep and 1 inch apart. They germinate in 5 to 7 days and are ready in 25 to 30 days.
Sow new seeds every two weeks for a continuous harvest. Radishes are perfect for interplanting with slower crops like carrots.
Beets
Beets grow well in cool soil and can be planted in March. Soak seeds overnight to speed germination. Plant 1 inch deep and 2 inches apart.
Thin seedlings to 4 inches apart for larger roots. Harvest both roots and greens. Beets store well in the refrigerator for weeks.
Onions
Onions are best planted from sets or transplants in March. Plant sets 1 inch deep and 4 inches apart. Choose short-day varieties for southern Illinois and long-day for the north.
Onions need consistent moisture and full sun. Harvest in 100 to 120 days. Green onions can be picked earlier.
Broccoli
Broccoli prefers cool weather and can be planted as transplants in March. Space plants 18 inches apart in rich soil. Use row covers to protect from cabbage worms.
Harvest central heads when tight and firm. Side shoots will produce later. Broccoli bolts quickly in heat, so early planting is key.
Cabbage
Cabbage is another cool-season crop for March. Set transplants 12 to 18 inches apart. Use a starter fertilizer high in nitrogen.
Harvest heads when firm and solid. Cabbage can tolerate light frost. Store in a cool place for up to two months.
How To Prepare Your Garden Bed For March Planting
Good soil preparation is critical for March planting in Illinois. Start by clearing away winter debris and dead plants. Remove any weeds that have sprouted.
Test your soil pH. Most vegetables prefer a pH between 6.0 and 7.0. Add lime if needed to raise pH. Add sulfur to lower it.
Amending The Soil
Work in 2 to 3 inches of compost or well-rotted manure. This improves drainage and adds nutrients. Avoid fresh manure, which can burn roots.
Add a balanced organic fertilizer like 10-10-10 at planting time. Follow package rates for your garden size.
Using Raised Beds
Raised beds warm up faster in spring than ground soil. They also drain better, preventing rot. Build beds 4 feet wide and 8 to 12 inches high.
Fill with a mix of topsoil, compost, and perlite. This creates ideal growing conditions for March vegetables.
Succession Planting For Continuous Harvest
Succession planting ensures you have vegetables all season. Plant small batches every two weeks. This works well for radishes, lettuce, and spinach.
For example, plant a 3-foot row of radishes every 10 days. You will have fresh radishes from April through June.
Interplanting Techniques
Interplant fast-growing crops with slower ones. Plant radishes between rows of carrots. The radishes are ready before the carrots need space.
This method maximizes garden space and reduces weeds. It also provides a continuous supply of fresh vegetables.
Protecting Plants From Late Frosts
March weather in Illinois is unpredictable. Frost can occur even after warm days. Protect young plants with row covers, cloches, or old blankets.
Remove covers during the day if temperatures rise above 50°F. This prevents overheating and allows pollination.
Using Cold Frames
Cold frames extend your growing season by several weeks. They trap heat from the sun and protect from wind. Build a simple frame with an old window or clear plastic.
Place cold frames over beds in late February. They warm the soil and air, allowing earlier planting.
Common Mistakes When Planting In March
Many gardeners plant too early or too deep. Check soil temperature before planting. Seeds planted in cold, wet soil often rot.
Another mistake is overwatering. March soil is usually moist from snow melt. Only water if the top inch of soil feels dry.
Ignoring hardiness zones is also common. Northern Illinois gardeners should wait until late March for most crops. Southern gardeners can start two weeks earlier.
Vegetables To Avoid Planting In March
Warm-season vegetables like tomatoes, peppers, and corn should not be planted in March. They need soil temperatures above 60°F and will die in frost.
Beans, cucumbers, and squash also require warm soil. Start these indoors in late March for transplanting in May.
Indoor Seed Starting For March
Start warm-season seeds indoors in March for transplanting later. Use seed trays with drainage holes and a sterile seed-starting mix.
Place trays under grow lights or in a sunny window. Keep soil moist but not wet. Harden off seedlings by exposing them to outdoor conditions gradually.
Best Vegetables To Start Indoors
Tomatoes, peppers, and eggplants need 6 to 8 weeks indoors before transplanting. Start them in early March for a May planting.
Broccoli, cabbage, and cauliflower can also be started indoors. They transplant well and mature faster.
Watering Tips For March Gardens
March soil is often wet from rain and snow. Overwatering can lead to root rot and fungal diseases. Water only when the top inch of soil is dry.
Use drip irrigation or soaker hoses to deliver water directly to roots. This reduces leaf wetness and disease risk.
Fertilizing March Vegetables
Cool-season vegetables need less fertilizer than warm-season crops. Apply a balanced fertilizer at planting time. Side-dress with compost tea or fish emulsion after 4 weeks.
Avoid high-nitrogen fertilizers, which promote leaf growth at the expense of roots and fruits.
Pest And Disease Management
March pests include aphids, slugs, and cutworms. Use row covers to exclude insects. Handpick slugs and snails at night.
Rotate crops each year to prevent soil-borne diseases. Remove any diseased plants immediately.
Harvesting March-Planted Vegetables
Harvest peas, radishes, and lettuce as soon as they are ready. Regular picking encourages more production. Leave root crops like carrots and beets in the ground until needed.
Kale and spinach can be harvested leaf by leaf. This extends the harvest period for weeks.
Extending The Season With Mulch
Mulch helps regulate soil temperature and retain moisture. Apply a 2-inch layer of straw or shredded leaves around plants. This also suppresses weeds.
Remove mulch in late spring to allow soil to warm up for warm-season crops.
Frequently Asked Questions
What Vegetables Can I Plant In March In Illinois?
You can plant peas, spinach, lettuce, kale, carrots, radishes, beets, onions, broccoli, and cabbage in March. These are all cool-season crops that tolerate frost.
Is It Too Early To Plant Tomatoes In March In Illinois?
Yes, it is too early to plant tomatoes outdoors in March. Start tomato seeds indoors in late March for transplanting after the last frost in May.
How Do I Protect My March Garden From Frost?
Use row covers, cloches, or cold frames to protect plants from frost. Water the soil before a frost event to release heat overnight.
Can I Plant Potatoes In March In Illinois?
Yes, you can plant potatoes in March once the soil is workable. Plant seed potatoes 4 inches deep and 12 inches apart. They tolerate light frost.
What Is The Best Way To Start Seeds Indoors In March?
Use seed trays with drainage, sterile seed-starting mix, and grow lights. Keep soil moist and provide 14 to 16 hours of light daily. Harden off seedlings before transplanting.
Final Thoughts On March Planting In Illinois
March planting in Illinois requires careful timing and preparation. Focus on cold-hardy vegetables that mature quickly. Use row covers and cold frames to protect from late frosts.
Start warm-season seeds indoors for a head start. With proper planning, you can enjoy fresh vegetables from your garden as early as May. Remember to check your local frost dates and soil temperatures before planting.
By following this guide, you will make the most of Illinois’ short spring season. Happy gardening!