Broccoli, being a cole crop, can be planted as soon as the soil can be worked. Don't plant it deeper than 1 inch from the root ball and not up to the first set of leaves. It does not grow new roots from the stem like tomatoes. The same for cabbage and Brussels sprouts.

Ok, valray - here comes the opposite advice, just to confuse you. You can certainly plant cole crops (brassicas) deeper than they were in their pots. And they do grow roots from the stems. You will see this if you have a big old brassica which has fallen over. There will be roots where it has lain on the soil. You can also see this happening if you have a cabbage in the fridge for a long time. Often roots will form around the cut end of the stem. This trait is very useful with overwintering brassicas such as brussels sprouts and purple sprouting broccoli as it increases their stability and helps them deal with the weather.

g'day valray,

if i get lanky leggy brassicas (includes broccolli) of any sort they all get planted deep to give the plant support, my experience is that they often do grow roots up the stem, anyhow least wise it works for me.

len

Here is a link that might be useful: lens garden page

The University of Illinois extension service says to plant broccoli only slightly deeper than the root ball.

Last year a few of my brocoli plants fell over and grew roots from where the stem touched the soil????????? not like the original root ball but it def rooted.

I'm not surprised that there's differing opinions on this. There wasn't a straight answer out there when I did my bit of research. It seemed like it might work - I've observed the roots on bent-over stems as well. Maybe I'll try deep-planting one or two seedlings and see what happens. It will probably be obvious fairly quickly if it's working or not and I'll report back.

Always planted deep due to low levels of light inside, always worked for me. Always read they will root up the stem. Although around here it isn't even much use growing broccoli in the spring due to our springs where the hot weather comes on pretty quick. Bolts every time, I guess I'll plant again in the fall.

Oh Flora UK! I got sooo excited when I saw mention of Purple sprouting broccoli...then I saw you are in the UK! pants! for a minute I thought I would find a supply in the USA! anyone in the US know if you can get it? to me it is a superior veg like asparagus, I like all veg, but these are in a class of their own.
my dad always refered to broccoli as we commonly know it as calabrese, he didn't rate it, at all, I like it but a bit of the purple sprouting stuff, what I would give... so if you know a source in the US let me know and you can have...? oh! I know! my first born son! he's 4 barely house trained but a keen digger...not always where you want him to but you could work on that...

valray,
I imagine you can set them out now...they like cool weather and it is best that they are not setting in pots any longer than necessary. Plant almost up to leaves if leggy. Also wind can break them off or lean them over if they are sticking up in the air.

UPDATE: Well it's been over a week since I planted my seedlings deep. They're doing fine so I think it's been successful. The stems would have rotted by now if they were going to, I think.

yes valray,

to gain confidence plant some of your seedling deep, we just planted ours and as always they where leggy plants so as always they are planted deep, and thriving. i realy can't understand why the boffins at a university would say different? might be vested interests involved??

len

for a minute I thought I would find a supply in the USA! anyone in the US know if you can get it? to me it is a superior veg like asparagus, I like all veg, but these are in a class of their own.

Funny you should mention that -- I just got my purple sprouting broccoli seeds in the mail a couple days ago and have them in bags to germinate. I've never eaten it before, but it looked interesting -- nice to know it comes well recommended!

I forget the place where I got it (they were cheap but took months to shop), but it looks like Baker Creek Heirloom Seeds carries it -- $2.50 a pack, $12 for a quarter pound. I've ordered from them before and they ship fast and all of the seeds I've ever ordered from them (except Stevia) have had good germination rates.

karenrei - I'm sure you've researched PSB and know it needs a long growing season. This year's are about 3 inches tall now (in seed modules in the porch). I am in the process of hardening them off and then they will be planted out in a couple of weeks. But I will not be harvesting until next Feb/March/April. (There is still a bit to harvest on last winter's plants) Do you think yours will overwinter in your zone? Also, if you have never grown it before be prepared for much smaller heads than on green broccoli. It looks like this. (Taken in April) {{gwi:38321}} But the flavour is terrific. You can eat the tender leaves around the head too. (BTW don't be tempted by the 1/4 pound of seed unless you are a farmer. It has very high germination and I would plant maybe four or five plants per person in your family.)

Growing season doesn't matter to me; I have a nice LED grow chamber now, so if I'm worried something won't make it, I'll just grow it in pots and take it indoors when it gets too cold.