The page says,"Broccoli, cauliflower, cabbage and kohlrabi heads grown for seed should not be trimmed for consumption." Which is sort of odd for them to say. If you cut the heads to eat, of course you'll get no seed, because the heads are the flower buds which you need to leave in place to flower and then go to seed.
So you need to grow more than you want to eat since some plants will be left for seed production instead of consumption.
Remy

Not true.... Broccoli flowers over and over. You can harvest the main head, and then more come off the sides. So I wonder if I cut the main head for consumption and then left the rest to flower, will the seeds be quality?

I wonder if this is to do with the quality of the seeds from later growth? With beans it is recommended to keep the best bean plants purely for seed, not just to keep any left over at the end of the season. Maybe the seed from the first large broccoli head is more vigorous than that from later side shoots? Perhaps the idea is to allow the plant to put all its energy into seed.

Also there may be a question of what any offspring will look like. If you are growing hybrids or have other brassicas around you may not get similar plants in the next generation. I wouldn't want to trade brassica seed for this reason. You don't know for sure what you are giving or getting. (Some of the kales, e.g red Russian, are good at not crossing and produce typical offspring.)

ok, good to know. My broccoli was the only brassica flowering , although I had others in veg state. Thank you.

I know broccoli make side shoots. I was saying it was silly the way they wrote. You can't cut broccoli heads and expect seeds.
Of course if you don't cut the side shoots for eating, you can save seed. It doesn't matter to the plant which heads the seeds came from. The plant is making side shoots in an attempt flower and make seeds. You won't get as many seeds since the smaller heads will make less seed. Smaller heads of broccoli from a group of plants for seed saving will attract insects. So you do need a group of plants still.
Broccoli is a shorter season crop so it is not like beans where harvesting most of the beans to eat and then leaving some to mature at the end of the season can be risky. Unless of course you are growing it as a fall crop in a cold area and you are not giving the plant enough time to develop side shoots and mature before winter, but you are in zone 9 so that is not a problem.
Remy

Cool, so even though there won't be as many seeds, you still believe the seeds I get from the side shoots will be quality?

Sorry I haven't been by in awhile, but yes, they will be good seed still.
Remy

Thank you! Case Closed!

Just a thought. Maybe because you would be selecting for later production. I've read that to select for earliness in say, tomatoes, you want to save seed from one of the first tomatoes. Might be the same idea in broccoli.

Yayanator,

just my two cents...

the largest, most vigorous seed definitely comes from the main flowering head of brassica species, though sufficiently good seed can still be saved from side shoots. do you have more than a few plants? ideally, 'outcrossing' species, such as broccoli, should have a large population (60-80 plants) pollinating eachother (some broccoli varieties can be 'self-incompatible') to avoid what is known as inbreeding depression. of course, you can save seed from just a few plants and go from there, but you may be better off buying seed from a reputable seller, and going big next year :).

all the best,
Winston

Thanks Winston, that was some really useful information. I couldn't wait for my plants to dry up anymore as I needed the space to plant new things so I chopped them off at the base and I am just going to hang dry them. I have many many pods and I was planning on saving the seeds. I am going to let my new broccoli grow from the root(s) I left in the ground. When I start new broccoli one day, maybe I will grow some from the seed I save and some from a different variety so that we don't get that inbreeding thing going on... sound good?

by the way - until I get that farm I want I won't be able to go big. I only garden in my front yard and it's about 15 x 30 with five big trees already sucking the life out of the soil!