You can transplant them outside before the last frost. After they are acclimated to outside temperatures, they will tolerate frost and freezing well. The planting date can be hard to determine. I think around April 1st is a good time to plant them outside. Before planting, I would monitor the weather for a week or so to see if the temperatures are fine. If temperatures are in the 50s for highs daily, and lows around 35-40, I would plant them. I would wait if the highs/lows are lower.

If you plant them on April 1st, then you want to start the seeds anywhere from 4 to 6 weeks before transplanting, depending on the size of plants you want. That would be around now.

Others in your zone may have a better time frame. Better yet, if you give your city and state or general area of the state, others can give an even better estimate since the USDA zones cover a large area with different climates.

Well, you can plant those plants outside well before the last frost date. In Ohio I plant them the first two weeks of April, light frosts or flurries do not hurt the plants. You want them to grow before summer heat to have the best edible quality.

I start those seeds here about March 20th for plant out about April 13th. I harden the seedlings outside for nearly the whole time except for cold snaps and heavy rains. I like to transplant them out when young...about 24 days getting excellent results. Crowding and root bounding are to be avoided while in pots.

Concur, Just be aware that greenhouse plants need to be hardened off before they will tolerate low temps. They may or may not show frost damage, but a quick cold shock will induce "buttoning" in broccoli and cauliflower. I avoid the problem by starting in coldframes rather than a heated area. 6-8 weeks before transplant.

Yeah, harden them off well. Then transplant them outside and they will eat the snow for breakfast. I agree that around April 1st would be good in your zone. Last spring (2nd week of April), my broccoli survived two consecutive nights down to 16 degrees F as well as countless nights in the 20s without any apparent damage. If you plan to put floating row covers on, you can start them even earlier (and you will need them anyway if you want to fight off those pesky Cabbage Whites).

I start them indoors only about 8 weeks before last frost then plant them out about 4-5 weeks before last frost with covers (milk jugs with the bottoms cut off). They start very fast from seed (2 days germination at 85F soil temp).

Getting an earlier start or setting them out earlier doesn't necessarily mean an earlier or better harvest. If the soil is cold when you plant them out (40's or below) they just sit there and don't grow anyway.

Mine are planted now and are going out in the hoop house March 1st ish. I need to get them hardened off first. I like to plant out a 5-6 week old seedling.

Jay

These are all great candidates for winter sowing. Check out the Winter Sowing Forum. It's very easy and you will have a hard time finding hardier plants.

Here is a link that might be useful: Winter Sowing Forum

I start broccoli on ~ Feb 26th. You must have a good light sourceor your seedling will get leggy. I aim to transplant somewhere between 4/1 and 4/15.