“Ive been feeding butterflies for decades with the Buddleia bush (Butterfly bush) and similar butterfly-attracting flowers. “
Monarchs can sip nectar from Buddleia but their caterpillars cannot feed on it. Asclepia milkweed is the food source for their caterpillars, plant some and you’ll do them a favor.
Dill weed works, too.
My yard is awash in Milkweed. I forgot to mention that. It was seeded by blown-in seeds so I created several guarded patches for the caterpillars to feed on. We’ve had a few over the years and my granddaughter has had the opportunity to watch them grow from eggs to caterpillars (they flew away before we could see them).
Unfortunately, former milkweed wild patches along highway roads have been cut down by about 70% so traditional breeding grounds are being eliminated by ignorance.