When should I sow my broccoli seeds indoors and when should I transplant outside?

1 Answer 1


Look up the last frost date for your zip code here. Duluth, for example, has a last frost date of May 21.

Or, as Ed Staub points out in a comment below, for a better picture of the situation go to the original source of the data at the National Climatic Data Center (1971-2000):

  • View the data sheet for your state.
  • In the "State and Station Name" column, find the observation station that is nearest and/or most like your location weather-wise.
  • In the row for 32°F, read across to the 50% column. (This means that there is a 50% chance of a temperature below 32°F after that date.)
  • This date is a reasonable time to transplant broccoli.
  • If you are going to cover the transplants -- which is an effective cabbage looper protection -- then you might be able to transplant a week or two early depending on how heavy your row cover fabric is.

You can transplant broccoli outside a week or two before the last frost date, and start the seed 4 to 6 weeks prior to the transplant date.

About a week before you transplant, start hardening off the plants: first set them outside on a moderate day for a couple of hours, avoiding winds or too much intense sunlight. Then set them outside for longer periods each day. This lets them acclimate to outside conditions so they don't get a sudden shock.

  • I'm in zone 4b so I'll probably put them in Feb. 12th along with Cabbage and Parsley. Thanks :) Jan 29, 2012 at 23:34
  • 1
    @LogicaLunatic: See this answer for info about what the USDA Zones don't tell you -- specifically your last frost date, which is the thing you need to know. Your zone is not relevant in this case. FWIW, I'd start the parsley 2-3 weeks earlier than the broccoli, and the cabbage seeds perhaps a week after the broccoli, though I'd transplant them all at about the same time. (Parsley seeds take a long time to germinate.)
    – bstpierre
    Jan 30, 2012 at 2:13
  • 3
    A better source for frost dates is to go to the source - the National Climatic Data Center (1971-2000). With global warming, you have to worry about stale data - I found one site listing dates from 1988, which are likely to be a week or two off. I don't see where the Old Farmer's Almanac gives a date, and the NCDC tables are a lot richer, too.
    – Ed Staub
    Jan 30, 2012 at 3:48
  • @EdStaub: Thanks, +1 to your comment. I've edited the answer to include that link.
    – bstpierre
    Jan 31, 2012 at 12:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.