Why Broccoli Didn’t Flower

Recently, a gardener asked our Master Gardener clinic why their broccoli didn’t flower. That question comes up regularly, and I’ve studied it in my own garden, with my own successes and failures.

Someone also asked me the other day if it was too late to plant winter brassicas.

Finally, I want to share a tip about what to do with your Brussels sprouts plants this time of year.

So I’ll tackle three brassica topics in this post. Here we go.

Why broccoli didn’t flower

If your spring- or summer-planted broccoli didn’t set its flower buds (the part we eat), it could be due to  planting at the wrong time, uneven watering, fertilization issues, planting bad starts or bad treatment of seeds or seedlings.

For summer harvest broccoli, timing is tricky, because you want to plant earlier in spring so you get the crop before the summer heat, but if you plant too early, the broccoli won’t get a robust start. If you plant too late, the heat stresses it. I’ve had best success when planting starts in early to mid-May (or doing a succession of plantings through May). That means you’ll be cutting heads in mid-July and into August.

In my experience, they like a lot of compost, which also helps to regulate moisture. So I put them in a well-composted bed, and add a top-dressing a few weeks after planting. I’ll feed once with a balanced complete organic fertilizer, about a month after planting.

Fertilizing with a lot of nitrogen as they’re trying to form heads could prevent the plant from flowering, and probably just produce more leaves.

For overwintering broccoli like purple sprouting (my favorite), I start the seeds in late May/early June, then plant them out in August. Also tricky to keep them consistently watered during that seedling stage. I top-dress with compost in mid-September, then lay a bed of straw mulch over the soil for the winter. They’ll send up a small central head by early March, followed by sprouts.

I don’t grow fall-harvest broccoli often, but I believe that it’s on the same planting and transplanting schedule as sprouting broccoli, but will produce heads in late September. I found the harvest to be small, so now I just concentrate on the sprouting ones.

Brussels sprouts ‘tip’

On to the Brussels sprouts. If you have winter harvest sprouts in the garden now, you’ve probably noticed small sprouts forming along the leaf axils. Also, you’ll probably see a denser set of leaves forming like at the top of the plant. If you cut off that growing tip, the sprouts should develop faster and more robustly. That’s because the plant is now putting all its energy into the sprouts rather than the new leaves.

Here are photos showing this cut on one of my plants:

Brussels sprout topBrussels sprout top cut

Planting brassicas now?

One final note about whether you could be planting brassicas now. The answer is, not really.Most brassicas should be planted in May and June, and transplanted in August, or at the latest in early September.

However! If you can find healthy kale plants still in the nurseries, you could put them in, but I would not expect much production from them over the fall and winter.

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