The common name Prairie Sunflower covers a few different species of Helianthus. From it's height and habit, it sounds like you have H. maximilianni, which is a super plant. I have a couple of clumps so far, from WS a few years back, and subsequent transplanting of volunteers, both from self-sowing and rhizome-like expansion.

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That clump is nearly 10' tall, and was trimmed back twice in late spring and early summer. My clumps are located in soil which is a little too fertile and a little too moist, so I have to support them, even after trimming them back.

When I root-prune them this year, I'm going to try a clump in a more arid location, to see if they will stand on their own.

I love this plant, but it needs to be kept in it's place. In good conditions, it spreads like crazy. The good thing is you can pull up and cut off shoots which are out of bounds, and simply stick them into the soil in the middle of the clump. They re-root immediately. I'm going to try this year's new clump in a buried bottomless pot, about 3' in diameter and 18" deep.

That IS a lovely plant. I like your bamboo support, Donn, did you make that? I had to take this plant out of my perennial garden. Over the course of 2 seasons, it literally "ate" a number of other perennials. It was too much work for me to try and keep it in check. I gave it to my friend who planted it out in her field, so it's always available if we need some! :)

Oh I am so glad you posted this!! Last summer (almost fall) I did a trade for some Helianthus plants (more like roots) and I put them each on the corners of the house. it looks like most of them are sprouting.

I am so glad they are so pretty!!!

I guess I need to watch them since they spread.

Karen

I whack mine back twice in late spring. However, I am going to have to move them as they are out by the street. Perhaps in the back yard next to my huge Norwegian spruce.

Yes, Mary, I made the support cage. It's 5' tall. Each upright is on a 4' piece of rebar, driven 2' into the ground, and you can just see a short piece of black poly tube at the bottom, which keeps the bamboo off the ground. You can't see them, but there are two grids of stout waxed cord tied into the cage to keep the stalks separated from one another.