(Picture from Washington Post)
This spring, I was pleasantly surprised to find that the mowing of our upper meadow after 3 years stimulated the small patch of Common Milkweed, that had already been growing in our meadow. Common Milkweed is the most prolific of the 12 native milkweeds in PA and is also know as Asclepias syriaca.
Our Milkweed have expanded to several patches and now includes roughly 1000 healthy individual plants.
Milkweed spread via seeds carried by the wind, birds or animals or by rhizomes underground. The mowing probably exposed fertile ground for the seeds and stimulated the rhizomes.
Milkweeds' milky sap contain poisonous glycosides, which the monarchs feed upon and can tolerate and in turn gives it the protection it needs from predators. Milkweeds' nectar and pollen are free of these poisons and provide food for numerous bees, butterflies and other insects.
It's well after May, and I have not spotted any monarchs coming through still.
Here is a map of the first adult sightings for North America through June 20th:
The milkweed are blooming, mature and ready. Hopefully, the monarchs will show up soon.