Sowing Options for Broccoli Seed Germination

For Fall Harvest:

Sowing in flats Indoors — Option 1

  • Fill the cells of a flat with starter soil mix.
  • Sow broccoli seeds at a depth of 1/4 to 1/2 inch in each cell.
  • Fill a mister bottle with water and mist the seeds and soil to water without disturbing them.
  • Cover the flat with plastic wrap to create a miniature greenhouse. Watch for moisture to cling to the underside of the plastic wrap in big droplets; if it does not, it is time to water your broccoli.
  • Place the flat in a sunny window with filtered light with indoor degrees average of 75 degrees, such as through curtains or blinds. Check the flat every day; seeds should germinate within a week.

Sowing Outdoors – Option 2

For a fall crop, seeds may be planted directly in the garden in late summer. Plant seeds at a depth of 1/4 to 3/4 inches, spaced 3 inches apart. They should be thinned to final spacing (about 16 inches) once they are established.  Watch your soil temperature as Broccoli seeds like 75 degree average temp.


For Spring Harvest :

Sowing Broccoli Indoors

For an late spring and/or early summer harvest, broccoli seeds should be sown indoors six to eight weeks before the last frost.  Plant seeds in a seed-starter kit or in small containers filled with seed starting mix, and place in a warm location. Follow the steps above for sowing in flats.  Keep moderately moist and allow drainage. Wait for seedlings to reach 3 inches tall before transplanting outside. This may take four to six weeks.

Sowing Broccoli Outdoors

Sow broccoli, a cool-season crop, directly into the garden up to four weeks before the last expected frost. These crops germinate within three to 10 days under optimal conditions and tolerate daytime temperatures as low as 40 degrees Fahrenheit.

Soil temperatures should be between 68 to 85 Fahrenheit, with an ideal range of 75 to 77 F, but seeds can germinate in temperatures as low as 40 F.

Planting too early in the year may when it is cold may cause them to “button” or produce tiny broccoli heads. But high heat may cause bolting, so in areas with warm summers like we have here in Georgia / Florida its best not to plant broccoli too late as the broccoli can not handle the hot soil.

Germination Time

While broccoli seeds prefer warm soil, sprouts will also emerge under cooler temperatures, albeit much more slowly. Seeds will germinate in about six days in 75 F soil. A seedling heating mat can be a helpful boost to germination time if you are starting seeds indoors. Seeds can be stored for up to three years in a dry place.

Plant seeds at the appropriate time and keep the soil evenly moist for quick germination.

Vegetable seeds, on average, germinate in about seven to 10 days. A few, such as radishes and broccoli, may germinate in three days; carrots and parsnips may take several weeks to appear.

Extreme soil temperatures may slow or curtail germination, as well as soil that is too dry or too wet. Follow the recommendations on the seed packet for planting depths and space, unless your soil is heavy clay. Then reduce planting depth slightly.

Direct-Seeded Crops

Sow cool-season crops, such as lettuce, kale, spinach, onions and broccoli, directly into the garden up to four weeks before the last expected frost. These crops germinate within three to 10 days under optimal conditions and tolerate daytime temperatures as low as 40 degrees Fahrenheit.

Plant semihardy vegetables, such as turnips, carrots, cauliflower, parsnips and potatoes, two weeks later. These crops typically take seven to 10 days, although carrots and parsnips take longer. Carrots germinate in 10 to 15 days; parnsips in 15 to 25 days. Wait to plant beans, corn and melon until the soil is warm and all danger of frost has passed. These seeds germinate within six to 10 days under optimal conditions.

Some crops, such as peppers and tomatoes, take so long to grow that they won’t mature before the first frost if sown from seed in the garden. Start these crops indoors four to six weeks before the last frost. Plant tomato and pepper seeds in seed starting trays, waxed milk cartons or even yogurt cups. Sow the seeds 1/8 inch deep in a soilless starting mix. Moisten the soil with a spray bottle and cover the seeds with plastic wrap until they germinate. Tomatoes germinate in six to 14 days; peppers in 10 to 20 days.


After seeds germinate and broccoli is growing, soil should be at 60 F and plants should be receiving plenty of full sun and moisture. Once true foliage appears, a light organic fertilizer may be applied. Broccoli is a heavy feeder and demands plenty of nitrogen, so it should be monitored for signs of nitrogen deficiency such as yellowing leaves, and fertilized accordingly. Maturing broccoli plants prefer soil in the pH range of 6.5 to 7.5, with temperatures of 60 to 65 F.

Soil Temperatures

When seeds germinate is based, in part, on the temperature of the soil. In cold soils, many seeds such as bean seeds are slow to germinate, or may even rot, never germinating at all. Read the seed packet and wait to plant seeds until the soil is adequately warm. Conversely, cool-season plants, such as lettuce, kale and spinach, germinate best in cool soils and may not germinate well when planted midsummer for a fall harvest. Store these seeds in the refrigerator for two weeks prior to planting to increase the odds of successful germination.


Although some plants are drought tolerant once established, all seeds need moist soil to germinate. Moisten the soil before planting vegetable seeds and water lightly after planting, as well. Water at least weekly or as needed to keep the soil moist, but not soggy, which may cause seeds to rot. Don’t allow the soil to dry out because it forms a crust that is difficult for the growing plant to emerge through. Use a light hand so you don’t wash seeds away.


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