I am in PA and I planted tropical milkweed. It has attracted tons of monarch eggs. I like the way it looks, and it doesn't spread by runners which was important to me. I have found a few swallowtail caterpillars on my parsley.

I'm live in PA and agree with mostone about the tropical milkweed. It's the only kind I have here anymore. I don't have to worry about it spreading all over the place, the butterflies prefer it here to any other milkweed I've tried, and it blooms up until the frost. That takes care of the Monarchs.

Now, it just depends what kind of butterflies you want to attract and you can go from there with what kind of plants to plant. Both Black Swallowtails and Giant Swallowtails lay their eggs on rue (make sure it's Ruta graveolens). False nettle is a host plant for Red Admirals, Question Marks, and Eastern Commas. Cassia hebecarpa is host for Clouded Sulphurs, Clouded Sulphurs, Little Yellows, and Sleepy Oranges. Lupinus perennis is host for various types of butterflies. Violets are a host for various types of fritillaries. The Variegated Fritillary cats will also eat passionvine (as does the Gulf Fritillary, but you probably don't get those there). Baptisia australis (wild indigo) hosts a bunch of different kinds of butterfly cats. If you want to attract Zebra Swallowtails, plant paw paw trees, and you'll have the bonus of getting fruit from them. I could name many more garden plants, bushes and trees for you that are butterfly host plants, but I really don't know what you're looking to attract. For nectar plants I highly recommend Verbena bonariensis, which is a prolific seeder, but the butterflies just love it. I get more butterflies and a greater variety of them on that plant than any other kind that I have in the garden. Today I had dozens of Common Buckeyes and skippers on mine.
Cathy

I am in NJ. I recommend "Swamp Milkweed" (hate that common name) as a perennial here. there are the normal pink plus a cultivated white flower form. Very nice plant and much prettier in a garden situation than common milkweed. Orange Milkweed (A. tuberosa) is also an easy perennial for a sunny spot. Definately keep parsley growing for the swallowtails too. Native Joe-Pyes (Eupatorium) are great nectar plants for butterflies and perennials.

I'm in South Jersey. The things that get the most attention in my garden are plain old butterfly weed (a. tuberosa), a dwarf white buddleia, I believe the name was "white ball," (I have seen a lot of fliers get very territorial over it!) and zinnia. I highly recommend zinnia! I have several types growing and they all are appreciated, but the bright pink, single bloom varieties tend to go over exceptionally well. Last year I also grew "candy cane mix" zinnia from seed, and that bed was a very popular place in addition to being a striking flower in itself.

What I love about the "butterfly weed" is that I bought a pack of seeds last year, harvested the seed pods at the end of the season, and planted those seeds this year. The gift that keeps on giving!

Thanks for the great suggestions everyone! In the spring I think I'll start with the tropical milkweed for the monarchs and a few others for the other guys. Thanks for your help!

My property is a Monarch waystation and I attempt to grow about 12 different species of milkweeds. Asclepias is not the easiest genus to grow! I concur about tropical milkweed (Asclepias curassavica), it has pretty flowers, is fairly easy to grow, and the Monarchs just love it.

I can't grow enough of tropical so I supplement with common milkweed (Asclepias syriaca) both plants growing in my gardens and some wild-collected. This plant doesn't really make a good garden plant, because it spreads by runners, and pops up in slightly different spots each year, but I let it grow where it wants with some manicuring. It makes great food for the larger cats because it has large leaves, and they don't wilt too quickly.

If you don't have common milkweed already I wouldn't recommend planting it unless you have a semi-wild area or grow it where you can keep it "corraled", or perhaps mowed regularly at the edges. Then it is okay. It has a divine fragrance when it's blooming.

Cherry, ash, willow, sassafras, and poplar trees are good host plants. I have watched a female Eastern tiger swallowtail lay eggs on the Black cherry trees, but unfortunately she was about 30 feet up in the air!

Caterwallin, do you know what the botanical name of "false nettles" is? I would like to grow some nettles.

Terene, The botanical name of false nettles is Boehmeria cylindrica. I could try to save you some seeds from mine if they cooperate (never saved them before and hope I catch them after they're ripe but before they drop).
Cathy