[barley]

any ideas why Brussels blow open

every year they seem to grow away lovely and firm nice buttons then "BAM" they blow open 
still edible but prefer buttons than mini brassicas 

[Yorkie]

They need to be very very very firmly planted in the ground.

[barley]

thanks yorkie

will have to plant with my hob nail boots on next year 

[Aunt Sally]

DD. runs a heavy lawn roller over the ground before he plants his sprouts.  It can't be too firm !

[Flowertot]

And if they are tall and your site is windy, stake them so they don't move.

[Goosegirl]

I never dig my brassica bed the autumn before and, when planting out, I really ram my knuckles well around their planting areas but am careful not to touch the stem. Get hedging stakes with a pointy end, about 4' high and bang them in about 6"-8" from the plant. Tie in as necessary using that rubber twine-in-a-ball (which is often re-useable) so it doesn't cut into the stem as it thickens.

[azubah]

Which variety did you sow? I have had success only with f1 seed.

[barley]

can't remember which variety 

I never dig the patch over for next years brassicas but maybe the staking is not good enough

we get strong winds out here across the fields

[PudsTree]

The variety is key with Brussels Sprouts especially if your site suffers from strong winds. As someone mentioned earlier, go for the F1 ones, with Brussels Sprouts they really are worth the extra money.

[Goosegirl]

I too get very strong winds here, and staking has to be firm as the plants get quite heavy towards the end; also tying in regularly helps to stop the stems bending over as they grow. I think you can get sprout varieties of different heights too, so choose one with a smaller one.

[moose]

I'm on a very windy site and have had great success with Early Half Tall and Darkmar21. Don't need to stake the half tall 'cos they are but have done with the Darkmar.

[marcofez]

I'm on a very windy site and have had great success with Early Half Tall and Darkmar21. Don't need to stake the half tall 'cos they are but have done with the Darkmar.

I'm on a windy site as well.
Does the early half tall taste good and crops well as I'm looking for another brussel variety?
Cheers

[Totty]

Combine all the ideas already posted, use f1 seed (much more reliable, Montgomerie is exceptional IMO), stake em if they are a tall variety, extra firm ground, and not too much nitrogen rich feed.

Totty

[Glosterboy]

It would appear the very informative reply comments have covered most reasons of why some brussels can and do burst open. This morning up the lottie I got talking to an old timer (84 years young) whose brussels were immaculate. He said "Hard firm ground, don't manure the ground, it makes the soil too rich, 24 inches-ish apart and don't hoe around the plants. If there are weeds? Pull them out for minimal ground disturbance". His Brussels were not staked. Our lotties are not in a not too exposed area.

[moose]

Marcofez, the early half tall crop well and not being F1 if you get a fairly long cropping period. They taste like...................brussels sprouts. Seriously all I can say is we like them-even the kids when they were younger.
I've remembered that I've also grown Seven Hills which is a later cropper and is not as tall as some.