The wasps feed off the caterpillars, they are a part of the food chain. I normally just knock down the nests when they are in a bad spot, near the house or pathways I travel. As long as they are not in an area where I will get stung, I let them be. The butterflies and caterpillars are very sensitive to poisons, so unless the nest is in a bad place, has gotten too big to safely knock down, or the little bastards sting me, no poisons.
I have tried the tea, it has a really "planty" taste. I'd be happy to send you leaves to try or plants if you want to grow it. PM me for details.

I'm a little too far north to get very much fruit. Most of the fruits are quarter size, you can't see them until they get ripe, they from camo green to bright yellow. You end up with about a teaspoon of fruit in each one. Farther south where I grew up, the fruit is small orange size with large fleshy seeds. So thew answer is yes and no.

@glennlab My milkweed is volunteer; a previous owner may have started them. There are deer here, and whatever they like will not wait for butterflies.

@EdEarl Fennel, dill, and milhweed are not that tasty to deer which is probably why the butterflies have adapted to it as well as concentrating the poison to keep the birds from eating them.

If the success of this season of people rearing Monarchs in Michigan is any indication (some people have hit 300+ rearing) You should be seeing some eventually.
That said we've had REALLY bad years before. 2013 I saw 2, and I made the mistake of giving a plant away with the one batch of eggs on it early thinking there would be more. Truly horrific year in my area.

This year for weeks have had them passing by all day long. Someone in my neighborhood is a power house raising them. My humble record is 30 in a season.

The movement to rear all sorts of butterflies is taking off. I no longer feel guilty not rearing, but I keep the plants around & have a count of around a dozen sighted in chrysalis around front porch, and that's not including back yard. So it was a banner year in S.E. Michigan for the monarch.

@Qualia That's great. I'll keep looking.

@EdEarl My understanding is the migration is really a form of "chains" /"links" so we're at the end of our season here in Michigan in August/Sept. Yours should be longer. A lot of people up here who do rearing seriously order tags. I've wanted to do that in the past but the tags were always sold out by the time I thought about it.

@EdEarl there are some great butterfly rearing forums on FB. Everyone from rank newbies to experts chime in on it.
It blows me away what people rear nowadays. It's so cool. Monarchs have to be the easiest LOL

@Qualia I was going to mention that I had only seen one so far and that the fall migration should be starting anytime now, but I got distracted. I feel bad when I have less than a few thousand fritillaries, but they are a stay at home butterfly.

I have at least 4 adults that live on my porch, they are slowly moving up from Central America. Right now, I think they are wintering under my house, each summer for the last 15 years, we have had babies that find their way into the house.

@glennlab If it's the mediterranean gecko(they're flesh toned -translucent skin) those are not indigenous & draw triatoma bugs. You really don't want them around. I don't know that they really have predators otoh. Mexican vine snakes will eat them though.

@glennlab Being a Tx expat though I greatly miss seeing Carolina anole around. I used to make pets out of them as a kid. My thing was finding the biggest buffest male around, capturing it, putting one in a dry bathtub to get it used to handling, stuff it with flies, then let it go after hanging out.
Dearly Carolina anoles.