[argonaut]

Planted a number of Broccoli plants last winter ... they survived winter well.
However they are growing and don't much look like Broccoli plants I had last year.

The stems have gone long thin and very tall quickly ....
http://flic.kr/p/9AqYba
is this what is described as 'bolted'   and do I have to bin them.

[compostqueen]

That's run to seed, as you can from the seed heads at the top of the plant

If you give them to the chickens they would be delighted    If not, you could leave them as a treat for the birds who love them, the pigeons will eat them green parts and then you can compost what's left

[argonaut]

out they will come into compost then.   

what causes this, anything I could have done different.

[compostqueen]

They might not have all run to seed

I don't know as I'm not that clued up on them but it could be the hot, dry weather

[realfood]

The first question is what kind of Broccoli?
In fact, there are two different groups of Broccoli plants which are:-

Sprouting Broccoli or Brassica oleracea Cymosa group.

This type of Broccoli is sown in the Spring and usually eventually harvested in late Winter and early Spring. In other words, it is a group of hardy, over-wintering varieties of Broccoli to eat in late Winter and Spring. But just to complicate matters, there are now sprouting broccoli cultivars that are ready for eating in the Autumn.

Calabrese or Italian Sprouting Broccoli, or Brassica oleracea Italica group.

This type of Broccoli is sown in the Spring  and harvested in the Autumn and early Winter, as it is not frost hardy. Some catalogs also list the Romanesco varieties (look rather like green cauliflowers), in this group. The edible spears are usually shades of green.

It sounds to me if you have planted the first group. You need to pick the emerging buds before they open and steam them. Fabulous!! Picked a Carrier bag full today. The main edible part of broccoli is the immature buds which if left, will turn into the flowers.