Swamp Milkweed (Asclepias incarnata)

With our wet year, swamp milkweed flourished, which could be one reason why this species had the most monarch eggs and larva in my plot. They were also the only variety that bloomed the first year for me.  Here is swamp milkweed in my research plot with a 3rd instar monarch larva under one of the leaves.

Research was completed this summer by members of the Monarch Consortium to determine which type of milkweed attracted the most monarchs.  (Hopefully I'll be able to report about their findings in future blog posts.)  Every week, those of us with milkweed plots counted the number of eggs and larva on each of the 54 milkweed we planted.  We also took note of things like the condition of the milkweed, presence of spiders and aphids, and the amount of rain.  Of the 9 milkweed species in my plot, swamp milkweed was the species that had the most eggs and larva, with a total of 40 eggs and 17 larva counted throughout the summer.   Swamp milkweed are a tall, slender-leaved plant.  If you look closely at these swamp milkweed, you can see a 4th instar caterpillar on the end of a leaf, level with the 33" mark on the yardstick.