Fold the circle in half to mark the center line, and then unfold it. Fold it in half in the other direction, and unfold it to mark the exact center of the circle. Use the scissors to cut down one of the lines from the outermost edge of the circle into the exact center. Step 3 I mentioned a few weeks ago that not only do I have to lime my plot because our soil is so acid, but I also have to use brassica collars here to stop cabbage root fly. I have bought 180 of them this year so far and used the lot and I already had some from previous years which have been used as well. For consistent crops of tasty, high-quality caulis, it’s best to choose F1 hybrid varieties, and if you’ve ever had problems with clubroot disease, select resistant varieties. Look too for varieties with an RHS Award of Garden Merit (AGM), which shows they performed well in trials – see our list of AGM fruit and veg for RHS-recommended varieties of cauliflowers and many other crops.

You may find that staples will not work to secure the ends of the plastic sheet together. In that case, you might want to use glue to hold the ends together. Autumn varieties – sow indoors or outdoors in mid- to late spring. They are slightly slower growing than summer types and bred to withstand higher summer temperatures, although light shade in the middle of the day is beneficial. They grow best in cool autumn weather and should be harvested before the first frosts.

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We want a plant collar in the shape of a cylinder, with an open top and bottom. A few options that don’t require much work include: Protect seedlings and young plants from slugs and snails, and keep watch for aphids and whitefly, removing them before they multiply

Plants canbe protected by growing them under the cover of an insect-proof mesh. Horticultural fleece may be preferred for seedbeds as it will also help warm the soil. This can also help reduce other brassica problems such as cabbage caterpillars. It should be kept in place throughout the growing seasonTypically I recommend covering cole crops with floating row cover to keep pests away, but in the case of cabbage root flies, covering them too early may actually trap newly emerged adult flies underneath the row cover, so instead I turn to making cabbage collars to protect my plants. I put a collar around each plant by late April because the first generation of adult flies typically starts to emerge in early May through June here in my Pennsylvania garden. Making Cabbage Collars What You’ll Need: Cabbage root flies overwinter in the soil as pupae. When spring arrives, they pupate into adults, feed on flower nectar, and go onto breed and lay eggs over the course of the next five to six weeks. While you can certainly buy brassica collars for your plants, these simple tools are just too easy to make at home with materials from your recycling bin to not try at least once. Personally, I prefer cardboard. It is easy to work with and will ultimately decompose. Just follow these steps to make your own brassica collars: Cut the cardboard into a 6- to 8-inch circle, making one square for each susceptible plant in your garden. If you’re using recycled frozen pizza cardboard rounds, you’ll just have to cut them to a 6-to 8-inch diameter if necessary. Step 2