bad butterfly, please go away

There's been a couple of cabbage white butterflies fluttering around these days. Some little holes have started appearing on the kale and gailan too. And sure enough, with every little hole comes a little caterpillar... while with every big hole comes a very plump caterpillar. 

I took a moment to observe a butterfly. As they fly about, they seem to try to find a good leaf to land on. They sort of stay there for a moment, make this pivot-like movement, then continue off in flight. Like a detective snooping around behind a suspect, I take a look at the underside of the leaf. Sure enough, there's a tiny white egg, about 1mm wide.

Apparently these butterflies are really territorial, and at the community gardens, they made butterfly cutouts as decoys. I've tried the same here to see if it actually works. If not, then planting land cress as a plant trap is an alternative solution (scientifically proven!). As the story goes, butterflies tend to prefer laying eggs on land cress, the caterpillars are poisoned by eating the land cress leaves, and your kale and other brassicas aren't touched by butterflies or caterpillars.