I routinely pinch or cut back the really tall species of Goldenrod (Solidago), perennial Helianthus, and Asters. They end up being a bit shorter and blooming a bit later. This seems to help prevent them from flopping as much. I usually do this in June, but early July is probably not too late, especially if you have a longer growing season. In the wild part of the yard, I've observed that these species are grazed on by deer, so they are probably well-adapted to this type of pruning. Unfortunately this Spring, I've had tendonitis in wrists and elbows, so I haven't cut back much. Only did a little pinching. The Helianthus maximiliani will probably end up being 10 feet fall and flop all over everything. 8-O

I’ve been meaning for a while to update some of my posts. I really appreciate the helpful info I’ve gotten virtually every time I’ve asked for an ID and I thought you’d be interested to see what the plants I inquired about early in the growing season turned out to be. But first, one lesson I’ve learned is that I should put a marker next to plants that are mixed in with others for ease of reference. This post was challenging in that regard, so I just did my best. Also, the photos I inserted are tiny, not sure whether they’ll will re-size when I post. Goldenrod #1, photos taken late August. Solidago canadensis, perhaps?

Thanks for the comment. At first I thought it was Zigzag Goldenrod but thought I should clear it here. The leaves appear to be sessile to me. I only have this one clump, all the other Goldenrod I have are of the flowers on top variety. I don't know where I could have picked up any seeds some where else. This area where it's growing is not cultivated by me except for some woody shrubs I put there. More pics.

I revisited this post to get the exact ID. This goldenrod species is Solidago altissima, or more precisely the Solidago altissima complex which includes 3 varieties. The different varieties can occur together, and there can be specimens that exhibit intermediate stages between varieties. This photo shows Solidago altissima var. altissima on the left. The upper leaves are not reduced in size. The goldenrod on the right is Solidago altissima var. pluricephela. The inflorescence is elongated and the upper leaves are reduced in size. In this photo the shorter plant on the left is Solidago altissima var. pluricephela. The plant on the right looks intermediate showing traits from both Solidago altissima var. altissima and Solidago altissima var. pluricephela.