I don't think they can behave as perennials because when they reach the flowering stage, even if you cut off the flowers, the plant is still in the reproductive mode and will keep trying to flower. The seeds seem to take forever to mature - mine started flowering in March and just now are all the seeds mature. The seeds pod (though not a true pod) will begin to turn yellow and then brown. I've read that they will not mature after removing from the plant. Once the seed pods turn brown, they will crack open very easily if touched and the seeds will burst out. The seeds all begin to mature at about the same time, it takes about 3 weeks for all seeds to be dry, with the earliest flowering ones coming first. I haven't tested the germination of any of the seeds I saved yet. I will try a couple of the plants in the fall. I will have mystery plants though as I had Jade Cross E hybrids and Long Island Improved (open pollinated) flower at the same time and a few broccoli plants flower. The plants produce a very large amount of seed; I haven't counted but I can see thousands of seed from the small amount I harvested so far and I have about 10 plants total.

I recommend Jade Cross (Jade Cross E) as a hybrid crop. I grew these last year and they performed excellently. They did not have problems like I had with Long Island Improved Brussels Sprouts. I'm trying Gustus hybrids this year.

Last fall I planted Long Island Improved and Jade Cross E. The Long Island Improved did not do good; they only made open sprouts even though the temperature was less than 70 when they made sprouts. The Jade Cross E hybrids made excellent sprouts though. This year, I bought seeds for Gustus hybrids and will try them in my fall garden. I'm also going to try Long Island Improved to see if they will form correctly.

Had the chance to google the name of the place where I bought the starts. It is called KIS Farm. The link below (warning: Pop-ups) is to an article in the local newspaper that describes the various goals of the enterprise. Pretty interesting. Apparently, the clerk was author Jessi Bloom. Before you get all eponym-nic on me, note her book is titled, "Free-Range Chicken Gardens." A good book, but her name should've been.... let's see. A bloom is to a plant like a blank is to a chicken... Jessi Egg? Here is a link that might be useful: KIS Farm Article