Thanks Sally. In addition to variable rates of seed germination due to several environmental factors as Monarch Watch article points out, seed production is also limited by tricky to pollinate flowers and the need for cross pollination as most milkweeds are not self fertile.
To this last point of the necessity of cross pollenation, In the case of Common Milkweed (and other milkweeds), most of the plants in any given patch are basically clones of the original mother plant spreading via rhizomes to form a colony . Thus each colony needs cross fertilization from another non genetically identical plant or colony, a distant cousin!
For me this translates into not only planting Milkweed, but planting milkweed from several divergent sources.
Currently I have Common Milkweed from eight different sources within 100 miles of my patch.
(Thankyou Sallyg and Muddy1 and others!) Again, this is Common Milkweed I'm primarily speaking of...
