The first plants are common milkweed and the last two photos are of Joe Pye Weed, Not a milkweed but still a favourite nectar plant of the monarchs.
It is interesting that you have found no caterpillars on that milkweed, as it seems to be the red-stemmed variety that I asked about in another forum last year. With the exception of one patch (where there is no other choices), I do not usually find anything on this type either. My observattion, is that this is a tougher variety anf given the choice monarchs will lay eggs on the more tender green-stemmed plants or on swamp milkweed.
John Beaulieu & Brenda Stride
Midhurst, Ontario CANADA
MONARCH WAYSTATION NO. 553