Last year I transplanted one Maximilian Sunflower (Helianthus maximiliani) from a friend’s garden. In September there were buds and in October there were flowers. I didn’t note the height of those blooms, but from the photograph angles I would guess that they were no taller than 6 feet.
These are annuals, so last year’s plants dropped seed from which this year’s plants are growing. And growing they certainly are! Firstly, there is now a small cluster of plants instead of just the one. And secondly, they have reached a very impressive estimated height of 9-10 feet.
This is a photo from September 24. There were just flower buds at this point. The nearby Desert Willow tree is currently an estimated 12 feet tall.

And this is a photo from October 7, the day after I first saw blooms. The stems have splayed out more.

Here are the Maximilian Sunflowers with a 5 foot 2 inch measuring comparison!

I was cautioned by friends familiar with this plant to not water them at all. If Maximilian Sunflowers get any extra water, they can grow even taller and be more likely to fall over. So I have dutifully ignored mine and they seem to be thriving on that treatment.
Maximilian Sunflowers are native to grassland prairies, where there would be bunch grasses that are several feet tall. In that situation, the sunflowers would need to be tall to be found, and the grasses would help to hold them up. It is not uncommon for people here to grow them up against a fence for support, but with my “inside out” garden (with the turf on the outside) I don’t have that option.


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