Hundred of tropical MW sprouts - in MARYLAND!

[BlizzardNole]

Every year I plant a few dozen tropical milkweeds that I start under lights. I assumed they are annuals here in central MD. Last year, I let them grow higher than usual and they seeded heavily. After planting my garden around May 1st I kept seeing patches of these little weeds coming up everywhere. I'd pick 'em and they'd keep coming. Finally I let them come up to see what they are and to my surprise, I have hundreds of tropical milkweeds coming up everywhere! We had a fairly hard first half of winter - I lost a pink Pampas grass to the cold. Just how far north do these tropical MWs come up as perennials?

[Mona Miller]

Not necessarily perennial in Zone 7. Some years when allowed to seed, they will come up. Other years, I never see even one.

http://plants.usda.gov/java/profile?symbol=ASCU
The USDA map now shows it as a perennial in TN. Coastal areas. California.

For it to be a perennial it would have to come back from the root, not reseed.

[Wyvern]

Parts of MD are between Zone 6 or Zone 7... so some years it will be one zone and some years the other. This past winter seemed to be a solid Zone 7 and tropical mw's can survive. I have about a dozen tropical mw's I grew last year that died back to the ground and came back again this year. These are not new seedlings as my plants did not get a chance to even form seed pods (too many cats chewed them up)

[Mona Miller]

I've heard that some of the tropical milkweed varieties can also be hardier than others. Save some seed, if you can.

[Wyvern]

Definitely will try to baby them this year to get seeds.

[Mona Miller]

Some one in MS sent me some tropical that she said was more hardy. I have to get them planted. So much to do, that I don't have time for every thing--but do take time to enjoy the butterflies.