Open Grow Guide

When to plant vegetables

By Open Grow Guide Updated

The best sign that it is time to plant vegetables is the temperature of the soil, which is more reliable than the calendar. Once the soil is between 40 and 50 °F (4 and 10 °C), you can direct-seed peas, spinach, lettuce and radish. Warm-season crops need soil between 50 and 60 °F (10 and 16 °C) and will not mature if seeded directly in the garden. Many vegetables start indoors instead, a set number of weeks before they move outside. Seedlings move outside to begin hardening off two weeks before you plant them in the garden.

When: Late winter to early summer (Feb–Jun)

When to do it

Peas go in the ground first. Pea seeds germinate as long as the soil is above 40 °F (4 °C), and garden peas withstand frosts and light freezes, though the blossoms cannot. Sow them as early as the ground can be worked. Lettuce, spinach and onion seed all have a minimum germination soil temperature of 35 °F (2 °C). Wait until after the last frost before transplanting tomatoes, eggplants, peppers and summer squash. Do not plant corn seed before the soil at the 4-inch (10 cm) depth reaches 50 °F (10 °C). Beans need at least 60 °F (16 °C) at that same depth. Sow cucumber seed after the last frost date, once the soil is at least 70 °F (21 °C) at the one-inch (2.5 cm) depth. Plant potatoes once daytime temperatures reach 60 °F (16 °C).

What you need

Use a soil thermometer to check readings such as the 70 °F (21 °C) that cucumber seed needs at the one-inch (2.5 cm) depth. For starting seeds indoors, you need a sterile, soilless germination mix and flats. A heating mat keeps tomato seed flats at 75 to 85 °F (24 to 29 °C) for best germination. Your planting stock depends on the crop: seeds, transplants, garlic cloves, potato seed pieces or sweet potato slips. A protected outdoor spot, out of the wind, is needed for hardening off tomato transplants. For mulch, choose herbicide-free grass clippings, weed-free straw or other organic material, or use black plastic to raise the soil temperature. Tomatoes can be staked or caged, and staked plants can be spaced 18 to 24 inches (46 to 61 cm) apart, a bit closer than caged ones. Fertilizer goes alongside the tomato row when the first fruits start to enlarge. Plan on one inch (2.5 cm) of rainfall or irrigation per week for the vegetable garden.

Step by step

  1. Step 1

    Check soil temperature first

    It guides planting better than the calendar.

  2. Step 2

    Direct-seed peas, spinach, lettuce, radish now

    Soil should be 40-50°F.

  3. Step 3

    Confirm pea seed can sprout

    It germinates once soil tops 40°F.

  4. Step 4

    Sow peas as soon as soil can be worked

    Peas tolerate frost; blossoms do not.

  5. Step 5

    Sow pea seed at the right depth

    Plant 1-1.5 in deep, 1-2 in apart, rows 2 ft apart.

  6. Step 6

    Wait longer for warm-season crops

    They need 50-60°F soil and won't mature if seeded early.

  7. Step 7

    Start tomato seeds indoors

    Begin 5-6 weeks before transplanting outdoors.

  8. Step 8

    Start broccoli, cabbage, and cauliflower seeds indoors

    Begin 10-11 weeks before transplanting.

  9. Step 9

    Start eggplant and pepper seeds indoors

    Begin 9 weeks before transplanting.

  10. Step 10

    Start leek and onion seeds indoors early

    Begin 14-15 weeks before transplanting.

  11. Step 11

    Plant tomato seeds in a sterile mix

    Set them one-fourth inch deep.

  12. Step 12

    Keep tomato flats warm on a heating mat

    Hold 75-85°F for germination, then 70°F once seedlings emerge.

  13. Step 13

    Keep pepper seedlings warm

    Hold soil at 70°F for best results.

  14. Step 14

    Move seedlings outside to harden off

    Start two weeks before planting outdoors.

  15. Step 15

    Harden off tomatoes in shelter

    Start with a few hours of sun, then add more over a week or two.

  16. Step 16

    Harden off transplants gradually

    Start two weeks ahead, adding sun over 10-14 days.

  17. Step 17

    Keep seedlings in on windy, cold days

    Avoid wind and temperatures below 45°F.

  18. Step 18

    Give unhardened transplants a sheltered spot outside

    Add time outside daily for a week before transplanting.

  19. Step 19

    Wait for the last frost to transplant warm crops

    This covers tomatoes, eggplants, peppers, and squash.

  20. Step 20

    Check night temperatures before setting out peppers

    Transplant only once lows stay above 50°F.

  21. Step 21

    Check soil for cucumbers

    Sow after frost once soil hits 70°F at one inch deep.

  22. Step 22

    Sow cucumber seed shallow

    Plant one-half inch deep, vining types two inches apart before thinning.

  23. Step 23

    Wait for warm soil to sow pumpkin and squash

    They need 65°F at 2 in deep.

  24. Step 24

    Plant pumpkin and winter squash seed

    Set three-fourths inch deep, 24-36 in apart.

  25. Step 25

    Space pepper plants in the garden

    Set 18 in apart, rows 30-36 in apart.

  26. Step 26

    Dig a trench for tomatoes

    Dig 3-4 in deep, burying the stem to just below the lowest leaves.

  27. Step 27

    Strip lower leaves and plant tomatoes deep

    Set the plant 5-6 in deep; the buried stem roots and strengthens it.

  28. Step 28

    Space tomato plants by variety

    Give determinate types 2 ft, indeterminate 3 ft apart; staked plants can sit 18-24 in apart.

  29. Step 29

    Watch for tomato blossom drop

    It happens below 55°F or above 75°F at night.

  30. Step 30

    Water tomato transplants before and after planting

    Water well before, firm the soil, then water again after.

  31. Step 31

    Water the garden weekly

    One inch of rain or irrigation a week is ideal.

  32. Step 32

    Mulch tomato plants for moisture and warmth

    Use organic mulch 3-4 in deep, or black plastic instead.

  33. Step 33

    Fertilize tomatoes once fruit starts to enlarge

    Apply fertilizer alongside the row at that stage.

  34. Step 34

    Sow lettuce seed shallow

    Plant 1/4-1/2 in deep, rows 18-30 in apart.

  35. Step 35

    Time a fall lettuce crop by the frost date

    Sow about three months before first fall frost.

  36. Step 36

    Grow broccoli transplants, then harden them off

    Grow six to eight weeks for spring, five to six for fall; protect from freezing.

  37. Step 37

    Space broccoli rows and plants

    Set rows 3 ft apart, plants 1.5-2 ft apart.

  38. Step 38

    Grow broccoli at its preferred temperature

    It does best at 65-75°F.

  39. Step 39

    Check soil for corn

    Wait until 4 in deep soil reaches at least 50°F.

  40. Step 40

    Wait longer for extra-sweet corn

    Plant once soil reaches 65°F.

  41. Step 41

    Plant corn seed shallow

    Set it about 1 in deep.

  42. Step 42

    Space sweet corn rows and seed

    Set rows 3 ft apart, seed 10 in apart.

  43. Step 43

    Adjust spacing for small, early corn

    Space 8-9 in apart, rows 30 in apart.

  44. Step 44

    Check soil for beans

    Wait until 4 in deep soil reaches at least 60°F.

  45. Step 45

    Plant bean seed shallow

    Set all beans 1 in deep.

  46. Step 46

    Space bush-type bean rows

    Set rows 2-3 ft apart.

  47. Step 47

    Space bush-type bean seed

    Set seed 2-4 in apart in the row.

  48. Step 48

    Check soil for carrots

    Carrot seed germinates best at 55-75°F.

  49. Step 49

    Cover carrot seed lightly

    Cover only 1/8 in deep.

  50. Step 50

    Space carrot rows

    Set rows 12-18 in apart.

  51. Step 51

    Sow beet seed shallow

    Plant 1/2 in deep.

  52. Step 52

    Check soil for onions

    Onion seed needs 35°F minimum, 50-95°F optimum, best at 75°F.

  53. Step 53

    Check soil for spinach

    Spinach seed needs 35°F minimum, 45-75°F optimum.

  54. Step 54

    Check soil for lettuce

    Lettuce seed needs 35°F minimum, 40-80°F optimum.

  55. Step 55

    Check soil for squash

    Squash seed needs 60°F minimum, 70-95°F optimum.

  56. Step 56

    Check soil for muskmelon

    Muskmelon seed needs 60°F minimum, 75-95°F optimum.

  57. Step 57

    Check cucumber soil temperature

    Cucumber seed needs 60°F minimum, 60-95°F optimum.

  58. Step 58

    Plant potatoes once the ground warms

    Wait until daytime temperatures reach 60°F.

  59. Step 59

    Plant potato seed pieces

    Set 3-5 in deep, 6-12 in apart.

  60. Step 60

    Start cauliflower seed indoors shallow

    Press seed one-fourth to one-half inch deep.

  61. Step 61

    Direct-seed cauliflower outdoors shallow

    Plant one-fourth to one-half inch deep, three seeds every 18 in.

  62. Step 62

    Space transplanted cauliflower seedlings

    Space them 18 in apart.

  63. Step 63

    Start cabbage seeds indoors

    Begin four to six weeks before transplanting.

  64. Step 64

    Space hand-cultivated cabbage rows and plants

    Leave 24-30 in between rows, 18 in between plants.

  65. Step 65

    Space transplanted cabbage seedlings

    Space them 15-18 in apart.

  66. Step 66

    Protect cabbage seedlings from frost

    Cabbage seedlings are sensitive to frost.

  67. Step 67

    Plant garlic cloves

    Set most cultivars 1-1.5 in deep; elephant garlic deeper, 2-2.5 in.

  68. Step 68

    Space garlic cloves

    Space 4-6 in apart, depending on bulb size.

  69. Step 69

    Space garlic rows

    Set rows 6-12 in apart.

  70. Step 70

    Plant garlic early enough to root before freeze

    Set cloves in fall so roots form before the ground freezes.

  71. Step 71

    Make ridges for sweet potatoes

    Build them 8-12 in high, 12 in wide, rows 3 ft apart.

  72. Step 72

    Plant sweet potato slips deep

    Set slips 6 in deep.

  73. Step 73

    Space sweet potato slips on the ridge

    Space them about one foot apart on the ridge.

  74. Step 74

    Wait for warm soil before preparing sweet potato ground

    Wait until soil warms to 65°F.

  75. Step 75

    Plant sweet potato slips once frost danger passes

    Plant three to four weeks after your frost-free date.

Mistakes to avoid

Warm-season crops will not mature if you seed them directly in the garden. Transplanting before the last frost is another mistake, since tomatoes, eggplants, peppers and summer squash should wait until after it. Peppers also need nighttime lows above 50 °F (10 °C) before they go outdoors. Cabbage seedlings are sensitive to frost, and pea blossoms cannot withstand it. Putting tender seedlings outdoors on windy days, or when temperatures are below 45 °F (7 °C), is a mistake too. Unhardened transplants belong in a protected outdoor area, with their time outside increased each day for at least a week before transplanting. Tomato blossom drop occurs if nighttime temperatures dip below 55 °F (13 °C) or rise above 75 °F (24 °C). Corn seed should not go in before the soil at 4 inches (10 cm) reaches 50 °F (10 °C), and extra-sweet varieties wait until 65 °F (18 °C). Beans should not go in before the soil reaches 60 °F (16 °C) at that depth. Garlic set too late is a risk as well, since cloves need to be in early enough for a good root system to develop before the ground freezes. Depth matters for small seed too, so cover carrot seed only 1/8 inch (3 mm) deep.

How this page was made

  • Written with AI assistance from the sources listed on this page. AI is never the source of a fact.

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