Broccoli and Bok Choy in October

by Linda Carloni, ABG Board Member

Many experts recommend that broccoli and bok choy (as well as other cruciferous vegetables) be planted in the inner East Bay in February/March or from July through September. But I plant mine from seedlings in October. Planting in October risks slow growth if the autumn is cool. But I fear the cabbageworm more than the cold weather.

My first experience in growing broccoli was not a happy one. A friend gave me some lovely seedlings in September. I let them sit on the porch a few days. When I had time, I planted them in a well-composted bed and sat back to await my crunchy delicious vegetables. To my horror the seedlings slowly disappeared – every morning I would check them and every morning there were fewer intact leaves. Eventually I pulled out the remaining uneaten shards of the plants in disgust, shook them over the bed and was confronted with tiny green caterpillars wiggling all over the soil of the bed.

The first sign of the problem that caused my broccoli debacle (technically, the imported cabbageworm, or Pieris rapae) are the butterflies. Pretty things flitting around, with white wings lightly marked with black, frequently referred to as Cabbage Whites. But don’t be fooled by their beauty – they hide their single yellow eggs on the underside of the foliage. In about a week, the eggs hatch into tiny green larvae, or caterpillars. The caterpillars are voracious, quickly devouring pretty much any cole crop (cauliflower, cabbage, broccoli, kale and the like). The larvae start small – about a tenth of an inch, but rapidly grow to over an inch. They feed for around two weeks, pupate and then hatch in about 10 days to start another round of egg-laying. In California, there can be five generations in a year.

What to do? I didn’t want to use pesticides, and I’m a lazy gardener, so handpicking sounded like too much work. I didn’t really even want to kill them, as they probably serve some purpose in the ecosystem. I just wanted them out of my food crops. After doing some research, I’ve settled on two techniques:

Plant late

Cabbageworm butterflies markedly reduce in number as the weather gets cooler. Since we frequently get a stretch of hot weather in September, I delay planting my seedlings until October. This does, of course, risk slow growth in the late fall if we have cool weather.

Use floating row cover

If you can keep the butterflies from laying their eggs on your cole crop leaves, you can prevent the damage from those eggs when they hatch. So I lay down floating row cover. This is an incredibly light weight fabric that sits loosely right on top of the leaves. You can find it at groworganic.com or other garden suppliers.

I secure it loosely with random rocks, but you could also use earth staples. It should have enough looseness so the leaves will stay upright and have some room to grow. I use the lightest weight, as I’m not trying to shade the plants or keep them warm. Sometimes this lightest weight is called insect barrier – pretty self-explanatory! As soon as I reliably see no butterflies flitting about and the plants seem large enough to withstand a bit of damage if it happens, I remove the fabric.

Since I’ve used these two techniques, my broccoli and bok choy have produced satisfying crops; I hope these tips work for you.