Last Updated on October 9, 2026

How to Start Cabbage Seeds Indoors

Start cabbage seeds indoors 8 to 6 weeks before your last spring frost and plant them out 4 to 2 weeks before it. Sow 1/4 inch deep, keep the tray at normal room temperature with no heat mat, and the seedlings come up in about 6 days at 68°F.

Those are the windows the Plan My Garden planner uses for cabbage. Cabbage can also go in for fall, timed from your first fall frost instead (see the fall section below). To turn the weeks into dates, look up your frost dates by zip code or enter your last frost on my seed starting calendar.

The spring cabbage timeline

University of Maryland Extension allows cabbage, broccoli and cauliflower 4 to 6 weeks indoors, so treat 6 weeks, the long combination of sowing at 8 weeks and holding until 2 weeks before the frost, as the ceiling and try not to go past it. Utah State’s own transplant-readiness bar, 4 to 6 mature leaves and a well-developed root system, generally takes 6 to 7 weeks to reach, past that ceiling, so judge readiness by leaf count and roots rather than the calendar if the two disagree. Holding plants too long risks bolting: Maryland Extension’s page on bolting says cabbage family crops can send up flower stalks in response to cool or hot temperatures and long days, that overly mature, stressed transplants are more likely to flower too early, and that bolting often prevents a usable crop. Illinois Extension adds that the cold trigger is 35 to 45°F held for an extended stretch, more likely if plants go out too early or an unseasonable cold spell hits right after transplanting.

Cabbage germination temperature and days to emerge

Cabbage seed sprouts across a wide range. These numbers are from my seed germination temperature chart, which uses the UC ANR California Master Gardener Handbook table for temperatures and J.F. Harrington’s UC Davis emergence table for days.

Warmer is faster, but you do not need the extra heat. University of Minnesota Extension notes there is no need for a heating mat with cabbage. Normal room temperatures between 60°F and 70°F, with bright overhead light, give the best plants, and higher temperatures make tall, weak seedlings that are hard to handle without damage. At room temperature, plan on about a week to see sprouts.

Step by step

1. Moisten the mix. Wet the seed-starting mix in a bucket before you fill anything. I use a mix with compost in it, like Coast of Maine.
2. Pick cells or blocks. If you are just starting out, I recommend cell packs. Maryland Extension suggests cells of 4 to 9 square inches for broccoli and cabbage, and a 2-inch soil block (2 by 2 inches, 4 square inches) is at the small end of that.
3. Sow 1/4 inch deep. That is Minnesota Extension’s depth for spring cabbage. I put two seeds in each cell or block.
4. Cover, but skip the heat. A clear dome or plastic wrap keeps the mix moist. Set the tray somewhere in that 60 to 70°F room range.
5. Uncover and light up. Take the cover off as soon as the seeds sprout, which helps prevent damping off. Hang the lights 2 to 4 inches above the seedlings and run them 12 to 16 hours a day on a timer; tomato and cabbage family plants are prone to stretching toward the light, so keep them close (Maryland Extension).
6. Keep them cool. After germination, grow seedlings somewhat cooler, with 65 to 70°F days and 55 to 60°F nights (Maryland Extension).
7. Thin to one. Snip the weaker seedling at the soil line with scissors. Minnesota Extension warns that pulling it can damage the roots of the one you keep.
8. Water from below. Pour water into the tray and let the cells drink it up through the holes. For soil blocks I add about an inch of water to the tray daily or every other day.

Feeding is usually not needed: most potting mixes contain enough fertilizer to grow a seedling for at least 6 weeks, which covers the whole time cabbage spends indoors (Maryland Extension). The full method for every crop is in How to Start Seeds Indoors, and the supply list is in my step-by-step seed starting guide.

Hardening off and planting out

Cabbage goes out before your last frost, so the seedlings have to be tough first. Hardened cabbage tolerates frost and can go in among the earliest cool-season crops (Illinois Extension); it is the seedlings in the tray that are frost-sensitive (Minnesota Extension). Hardening off is the difference. Minnesota Extension also cautions against setting plants out before the weather has settled; hardening off, plus bringing seedlings in on nights below 40°F, is how to meet the planner’s window without exposing them to that risk.

Start 10 to 14 days before planting, a few hours outside out of direct sun at first, then a little more time and sun each day. For the day-by-day version, see my hardening off schedule, which spreads the same idea over 7 to 10 days for crops in general; for cabbage, follow the 10 to 14 day window above. Minnesota Extension adds three cabbage details: reduce watering once the plants have five true leaves, give them wind protection while they adjust, and bring them back indoors on nights below 40°F. A cold frame makes the job easier.

Plant out 4 to 2 weeks before your last frost. Utah State University Extension puts cabbage transplants in 2 to 3 weeks before the last frost: they should have 4 to 6 mature leaves and a well-developed root system, and cabbage is not seriously damaged by temperatures down to 25°F. Set each one at the same level it grew in its pot and handle it gently, since damage to the central growing point of a young plant can stop it from forming a head (Minnesota Extension). My transplanting guide covers watering in and mulching.

Cabbage is hardy on my vegetable frost tolerance chart, which has you cover it on nights below 24°F. For a cold snap right after planting, Utah State recommends hot caps and fabric covers to protect seedlings and transplants from frost. Spacing is one plant per square for compact varieties, as on How Many Cabbage Plants per Square Foot?

Why spring timing matters for cabbage

Starting indoors is what gets cabbage to head before summer heat. Sow too late in spring and the crop matures in the hottest part of summer, with poor quality (Minnesota Extension). Cabbage grows best under 80°F; higher temperatures cut growth and quality (Utah State).

Starting cabbage seeds for a fall crop

Fall cabbage is timed from your first fall frost, not your last spring one. The planner’s fall schedule gives deadlines: start seeds indoors by about 10 weeks (68 days) before your first fall frost and set transplants out by about 5 weeks (33 days) before it. It also gives a direct-sow window of 12 to 9 weeks before the frost. Those dates run late because cabbage is hardy and tolerates below-freezing temperatures late in its growth (Minnesota Extension).

Treat the two transplant dates as the latest you can go, not the target. To time a specific variety, use Utah State’s method: choose an early-maturing variety and aim for it to mature about 1 to 2 weeks after your first fall frost. Count back from that harvest date by the variety’s days to maturity. For a 60-day variety, that is 46 to 53 days, about 7 weeks before the frost, which is earlier than the planner’s deadline. Iowa State University Extension also recommends only early-season cultivars for fall, started indoors 4 to 5 weeks before planting them out.

Summer seedlings need different care. Illinois Extension suggests putting seed flats where they get some protection from the sun in summer and transplanting on cloudy, overcast or rainy days to cut shock. Keep them watered: irrigation is especially important for fall plantings (Illinois Extension), and an inch of water a week is enough for cabbage (Minnesota Extension). Harden fall seedlings off the same way, starting in the shade. My fall crop planting guide covers what to plant where the summer crops finish.

Where to get cabbage seed

Wood Prairie’s organic cabbage seed includes the early varieties Red Express (60 days) and Golden Acre (62 days), plus All Seasons and Filderkraut. Code PMG5 takes 5 percent off.

Quick questions

When should I start cabbage seeds indoors?

8 to 6 weeks before your last spring frost, then plant out 4 to 2 weeks before it. For a fall crop, the Plan My Garden planner has you start seeds indoors by about 10 weeks before your first fall frost and set transplants out by about 5 weeks before it.

How long do cabbage seeds take to germinate?

My seed germination temperature chart gives 5.8 days at a 68°F soil temperature, 8.7 days at 59°F, 14.6 days at 50°F and 4.5 days at 77°F. At normal room temperature, plan on about a week.

Do cabbage seeds need a heat mat?

No. University of Minnesota Extension says there is no need for a heating mat with cabbage. Normal room temperatures of 60°F to 70°F with bright overhead light give the best plants, and warmer rooms make tall, weak seedlings.

How deep do you plant cabbage seeds?

1/4 inch deep, which is University of Minnesota Extension’s depth for spring cabbage started indoors.

Why did my cabbage bolt instead of making a head?

University of Maryland Extension says cabbage family crops can send up flower stalks in response to cool or hot temperatures and long days, and that overly mature, stressed transplants are more likely to flower too early. Illinois Extension adds that the cold trigger is 35 to 45°F held for an extended stretch. Plant out after about 4 weeks indoors, not 6 or more.

Get your cabbage start weeks as dates

The planner turns your zip code’s frost dates into cabbage start-indoors and transplant dates. Plan My Garden is free to start: enter your zip code and it finds your frost dates, draw your beds, pick cabbage and everything else you want to grow, and it places each plant at square-foot spacing and builds a planting schedule (start indoors, transplant and direct sow dates) from your frost dates.

Related: How Many Broccoli Plants per Square Foot? · How Many Brussels Sprouts Plants per Square Foot? · How Many Collard Plants per Square Foot? · Seed Starting Calendar