Elana, good questions about the perennial kale! I've have some perennial collards and have been wondering some of the same things.
Elena Brooks wrote:They've already been attacked by the cabbage white caterpillars (I only got them in September). How do you deal with that problem? Do you net them or share the harvest with the wildlife? Can they survive the slug/snail/caterpillar damage (that's a more pressing question for the edible landscaping project obviously as would be left to tend to itself)?
I find that daily checking and hand picking the caterpillars helps a lot. I've also make a spray that is very effective against cabbage moths.
3 C fresh mint
2 bulbs fresh garlic
1 or two fresh cayenne peppers or 2 tsp cayenne powder
3 qts water
biosafe dishwashing soap
Chop garlic (no need to peel), mint, and cayenne peppers (wear gloves for fresh cayenne!) Place these in the water in a pot and bring to a simmer. Cool and strain into a spray bottle. Add a squirt of soap. Spray it on your cabbages, kale, collards, etc., undersides of leaves too. It has to be re-applied after rain or watering. I've brought badly eaten plants back to thriving with this spray.