Why Are My Brussels Sprouts Blowing Out?


I don’t normally grow Brussels Sprouts. Why? Because the majority of people in my family profess to not liking them. But this year I had the room, and the seeds and well… one thing led to another.

The upshot was that I ended up with a row of Brussels Sprouts in my Winter garden. They looked happy and were growing strong until about a month ago when the ‘buds’ started to appear. I went away for a week and when I came back I found this. Not tight little round balls ready for harvest but mini-cabbages glued to the side of the stalk.

This is called ‘blowing out’. Instead of staying compacted the sprouts open up like, well like ermm.. Cabbages. This is not what I expected to see. So why did this happen? Is my soil not right? Did I plant them too close together? Should I have fertilised them? What?

There could be a few reasons.

Soil too Loose
I suspect the main reason is that I didn’t firm them in hard enough. Brussels, like Cauliflowers like to be snug so the soil needs to be firmed before planting and pushed in (with your foot) all around the plant. I confess I didn’t do that. Brussels Sprouts get quite tall and when they rock in the wind their roots can snap resulting in ‘blowing out’.

Soil Too Acidic
Brussels Sprouts (like many Brassicas) will fail if the soil is too acidic. We’re aiming for a pH of 6.5-7.5 so lime the soil to correct it. When I tested my soil at the beginning of the season it was around 6.5 but my soil has acidic tendencies and I suspect if I tested it now it would be more on the acidic side.

It’s unlikely that it is the variety I chose. It was Long Island Improved, an heirloom variety. While some F1 hybrids claim resistance to blowing out they would probably succumb given the wrong growing environment too.

So… you live and you learn. That’s what I love about vegetable growing. And, armed with this kind of knowledge, there’s always next year!

7 Comments on “Why Are My Brussels Sprouts Blowing Out?

  1. I’ve been following your blog for quite a while now. I really enjoy reading your posts. Gardening is all about learning as you go. There’s a touch of alchemy and lots of luck involved too.

    I am hoping to grow some winter veg this year and lots more seasonal veg on my very tiny plot this year. When I plant out my seeds, I always wonder who the winners and who the losers will be.

    Leanne xx

  2. What a shame. I don’t know why it’s happened, I haven’t grown sprouts before (hopefully next year), but I do remember it happening a bit when I was little and we had a veg garden. Let us hope that next year they are successful – it would be lovely to have home-grown sprouts on the table at Christmas. Or not, depending on your point of view. I love them though.

  3. I find this happens much more with wind-rock loosening the plants, rather than soil deficiency/acidity. You can’t plant brassicas too firmly, and I normally stake them for good measure.

    There’s the old test for whether you’ve planted the seedling firmly enough: tug on one of the leaves. The leaf should break, rather than the plant pull out.

    On the plus side — blown sprouts still taste good. You can use them shredded, instead of whole. Try stir-frying them?

  4. Are the sprouts still edible after ‘blowing out’? I think they get a bad rap. I didn’t like them as a child, which seems to be common, but I love them as an adult! Thanks for sharing your sprouting experience with us!

  5. How disappointing! I’ve never heard of this phenomenon but then I’ve only grown Brussels sprouts a couple of times. I plant to again this year. Was also unfamiliar with the need to firm the soil. My soil is so clayey I’m hesitant to press it down at all except the space immediately around my tomato stakes.

  6. Oh I adore brussels… I love to eat bowlfuls of them. I so wish I could grow them. Alas, it’s too hot where I am and they never get sprouts!