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vegetable seeds to plant outdoors in cool spring temperatures

7 early spring vegetables

It’s not unusual to be dreaming of planting your garden in the middle of winter. Fortunately, there are quite a few different early spring vegetables with hardy seeds that can be planted outdoors in cool temperatures. Crops like carrots, peas, and lettuce are perfect early spring vegetables for your outdoor garden!

early spring vegetables - vegetable seeds to plant outdoors in cool spring temperatures

1. Lettuce

Lettuce is another favorite early spring crop to direct seed. Lettuce seeds can germinate at exceptionally low temperatures. While these seeds can germinate at 32°F (0°C) over several months, lettuce seeds germinate in about a week at 50°F (10°C) soil. The optimal temperature range is 60°-75°F  (16°-24°C).

Lettuce can be seeded throughout the spring for a continuous crop. Some gardeners prefer leaf lettuce (like Black-Seeded Simpson) while others like to mix in some head-forming types of lettuce. See my favorite vegetable varieties to grow for recommendations.

2. Carrots

Carrot is one of my favorite early spring crops. Carrot seeds can germinate in soil temperatures from 40°-95°F (4°-35°C), although optimal temperatures are in the range of 65°-85°F (18°-29°C).

I tend to plant my carrots outdoors about 4 weeks before the last frost date. Gardeners using a cold frame or frost cover may be able to direct seed 8-12 weeks before the last frost date. Spring-grown carrots are usually harvested in early summer to make way for warm-season crops like tomatoes and peppers. A second fall crop of carrots can be seeded in late summer for a late fall-winter harvest.

3. Onions

Onion seeds – particularly green onion seeds (scallions) – can be sown quite early in the spring. These cool-season seeds can germinate (albeit slowly) in soil as low as barely above freezing (32°F/0°C). That said, onion seeds can germinate in a week at 59°F (15°C), and have an optimal soil temperature range of 65°-85°F (18°-29°C) for germination.

Most gardeners harvest whole green onion plants at once, pulling up the entire plant (roots and all). Try to harvest alternating plants as you move down a row or through a square foot to allow the remaining plants extra room to receive sunlight and water.

4. Peas

Pea seeds are another early spring favorite. Peas have large seeds that germinate when soil is between 40°-85°F (4°-29°C). That said, peas germinate much more quickly in the range of 65°-75°F (18°-24°C). Get these seeds in the ground before spring temperatures get too hot!

Peas are generally sown in early spring for a late spring/early summer harvest. A second crop can be sown in the fall, particularly in areas with mild autumn temperatures.

5. Beets

The beet is a classic early spring garden vegetable. Beet seeds germinate in a wide range of temperatures, sprouting when soil is anywhere between 40°-95°F (4°-35°C). While beet seeds can germinate in soil as cool as 40°F (4°C), they germinate much more quickly in the range of 65°-85°F (18°-29°C).

I like to plant my beet seeds outdoors when the soil reaches about 60°F (15°C). Beet seeds should take about 10 days to germinate at 59°F (15°C), but the seeds usually germinate more quickly because soil generally continues to warm after the seeds are planted.

The wide range of germination for these seeds makes this a perfect veggie for early spring planting and for succession planting throughout the growing season. Start planting your beet seeds in the early spring as soon as soil can be worked. Continue seeding beets every 2-3 weeks for a continuous harvest.

6. Spinach

Spinach seeds are very well suited to germination in cool spring temperatures. Like lettuce, these seeds can germinate at 32°F (0°C) over several months. Spinach seeds germinate in about 12 days at 50°F (10°C) soil. The optimal temperature range for germination is 65°-75°F  (18°-24°C).

Spinach crops grow best in cool temperatures and tend to bolt (prematurely growing seeds rather than harvestable leaves) as temperatures become warmer in late spring/early summer. Look for bolt-resistant varieties in areas with hot summer weather to extend your late spring harvest.

7. Radishes

Radish seeds are often the quickest vegetable seed to go from planting to harvest in the cool-weather spring veggie garden. Seeds germinate between 40°-95°F (4°-35°C) with an optimal soil temperature range of 65°-85°F (18°-29°C). 

In optimal temperatures, radish seeds usually germinate in less than a week (and small varieties are sometimes ready for harvest in under a month). Radishes can be planted through the early spring for a continual harvest of tender young radishes.

Outdoor seeding basics for early spring planting

Seeds for many cool-season early spring vegetables can be direct seeded outdoors for 4-6 weeks before the local last frost date. Gardeners with cold frames or frost cover may be able to plant 6-8 weeks before the last frost date as long as the soil has thawed and can be easily worked with a handheld trowel.

Seed germination is affected by many different conditions, including the health of the seed itself, soil moisture, and soil temperature. In general, many vegetable seeds germinate very slowly or not at all at near-freezing temperatures (and most seeds stop germinating at temperatures over 100°F (38°C).

That said, seeds for many “cool-season” early spring vegetables will germinate at temperatures as low as 32°-40°F (0°-4°C) (source: University of California). Germination is quite slow at these low soil temperatures, but planting is certainly possible. The speed of germination for these cool spring vegetable seeds usually increases rapidly as the garden soil warms up in the spring.

Planting vegetable seeds outdoors in cool early spring temperatures is easiest with a soil thermometer. I use a soil thermometer with a 4” probe to measure the temperature of my vegetable garden beds prior to direct seeding. Check soil temperatures for a few days prior to sowing, looking for a consistent pattern of either stable or steadily warming soil.

Soil temperature chart for germinating seeds outdoors in cool weather

Here is an overview table giving approximate optimal temperatures and days-to-germination for the cool spring vegetable crops listed above:

Summary Table: Estimated Vegetable Seed Germination At Cool Spring Temperatures

CropMinimum Soil Temperature for GerminationOptimal Soil Temperature RangeGermination Time at Soil Temperature of 59°F (15°C)
Beet40°F (4°C)
65°-85°F (18°-29°C)
10 Days
Carrot40°F (4°C)65°-85°F (18°-29°C)10 Days
Lettuce32°F (0°C)60°-75°F  (16°-24°C)4 Days
Onion32°F (0°C)65°-85°F (18°-29°C)7 Days
Pea40°F (4°C)65°-75°F (18°-24°C)9 Days
Radish40°F (4°C)65°-85°F (18°-29°C)6 Days
Spinach32°F (0°C)65°-75°F (18°-24°C)7 Day

Reference: https://sacmg.ucanr.edu/files/164220.pdf 


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