I just bought a milkweed plant at my local Farmer's Market. Then, I learned that monarch caterpillars eat the new growth of seedlings. Do you if that means this mature plant won't help them? I'll let it go to seed, either way.
Discussion
The caterpillars can eat any of the growth. Adults often seek out tender new growth to give them the best chance at survival. That often means a seedling at the edge of a patch or a shoot from a recently pruned milkweed.