Plant Doctor Archive

Brassicas not their best

I'M having trouble growing brassicas. I end up with lots of leaf but no hearts. The soil grows potatoes, carrots, beans, peas, beetroots, corn and tomatoes well, but not brassicas. What are the optimum conditions for them?

OBVIOUSLY your soil conditions are good, so I think it must be timing. Most brassicas, including cauliflower, broccoli, Brussels sprouts and cabbage, grow best in cool conditions and, in warm parts of the country, often don't do so well through the heat of summer. They can grow during summer, but the high temperatures can prevent hearting and they'll go to seed much more readily.

The ideal time to plant is in mid to late summer and into autumn, so they do most of their growing through the cooler months.

Broccoli is a little more tolerant then the others of warm growing conditions and can be quite productive through spring and into early summer in some areas. They need reasonably moist, fertile conditions to encourage leaf growth, so it may pay to sprinkle a high nitrogen fertiliser around each plant a couple of weeks after planting and again a few weeks later. But if you mixed lots of compost into the garden for your summer tomato and corn crop, there may still be plenty of nutrients left for the brassicas.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.