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.

I'm in Boston Metro and have had my calui and broccoli in for a while now. Planted them 3/15 (had to do some covering until about a week ago). You can plant them, we should be in the clear. On the other hand, we live in MA, so anything is possible :)

Sorry for the delay. I've moved almost everything outside. I still have a few late started flowers inside but all the veggies have been planted in the garden. I've been pretty busy with my new containers. My neighbor had som pretty large fiberglass containers he used for raising worms. He no longer uses them so I asked and he gave me a couple to make a raised container garden. I've got one planted and am ready to put the other on blocks. It took $50 worth of soil to fill the first one and it's not quite full but that's ok because after I've trimmed the bottom leaves from the tomatoes planted in it I can finish filling it so the plants can make more roots where the bottom leaves were. Back to the subject, it's starting to get hot here so I imagine I will be working more on the inside planters now to stay cool. One problem I have is the window boxes I have are just a little too long for the windows so I've got to buy a shorter one or use smaller containers. I like the window boxes because they have their own tray. I'm guessing the broccoli and cauliflower is out because they take more light but what about cabbage? Anyone ever grown it inside?

Brassica are cool-weather plants that you may want to consider an autumn/winter crop every year. My mother soaked my father's garden vegetables in a kettle of cool salty water to drive out the bugs before cooking. I was an unobservant kid, so I don't know if it worked, but I do remember holes in the leaves and no worms at dinner, so I guess it worked. ;-) Note that after you get big central broccoli heads, you'll get numerous smaller side forets for the rest of the season, so don't discard the plants. The little florets are great for stir-fry, or you can toss them in your pasta water for the last few minutes of boiling, drain together and dress with olive oil, chili flakes and grated cheese for a quick easy meal that features all your garden successes. And wishing you many gardening successes in the New Year!