Why broccoli goes 'blind'

Brassicas and I frequently don't see eye to eye. For every Savoy cabbage that plumps up like a football, there'll be two more that never really get started.

And yet I'm lucky in many respects. I don't have cabbage clubroot, or cabbage root fly. A lot of whitefly, yes, and if I don't throw a net over the plants, the pigeons and the caterpillars think all their Christmases have come at once. But in general, I think I'm just a bit inept at growing brassicas. I'll grow cavolo nero (and wonder why it grows so much better in the Secret Garden, pictured above, than on my own plot), and purple sprouting, Chinese broccoli (kailans) in spring and reasonably satisfactory broccoli for the winter. The kailans are a bit of a law unto themselves but the others are pretty reliable.

I'm also improving with the broccoli Romanesco - often called cauliflower Romanesco. This most delicious and intriguingly beautiful of brassicas is the plant which produces pale green fractal whorls in a triangular tower. It looks more like a science project viewed under a microscope than a vegetable. It's delicious to eat - especially with an anchovy sauce, or with bacon lardons - and difficult to find in shops outside farmers' markets. All of which goes to make it one of the first items on the allotment Most Wanted list.

This year, we've had a couple of good meals with some medium-sized heads. but I notice that about a third of the plants have come up 'blind'. Instead of a bud, or head, there is just a bare green stub at the centre of the plant. The leaf growth however is noticeably abundant.

That little stub in the middle? That's where the central stem should normally throw up
central bud, or cauli head.

And here's one I made earlier, complete with head full of those
distinctive edible whorls.

Research on the web and in my text books suggests that this is due to the prevalence of low temperature when the plants are young or due to damage to the terminal bud during handling the plants or due to injury by pests

or 

drying out at seedling stage

or 

Swede midge (Dr D G Hessayon, The Vegetable and Herb Expert)

or 

any of the above (Stefan Buczacki, Pests, Diseases and Disorders of Plants).

The drying out suggestion makes the most sense to me. We had low temperatures until very late spring, but I didn't plant them out until June, by which time we were well over the winter chill. I'd never heard of Swede midge before now, but I've examined the plants very carefully and can't find any traces of insect activity at all.

Broccoli, like so many other veg, dislike any check in their growth, including a sudden drought. Something to look out for next year, when hopefully they will all produce beautiful green caulis.