Ask Mr. Smarty Plants

Since we have no personal experience with Helianthus maximiliani (Maximilian sunflower), we would like for you to read these comments from Dave's Garden.  If it does, indeed, grow large, spreading roots, you would have to divide it and repot every year. Several of the comments referred to it as invasive and difficult to control. In terms of a pot up on bricks in a tank, that sounds very unstable. We are talking Central Texas, right? And what do we have in Central Texas? Wind, right? These plants get up to 8 to 10 ft. tall, and are somewhat top-heavy, the stalk often bending over with the weight of the big flowers and seeds. We think the first good breeze you have, your sunflowers will have to learn how to swim. 

We don't want you to think we don't like Maximilian sunflowers, we do, but they just really aren't what we would call container plants.  Unlike most sunflowers, they are perennial, and reproduce not only from seeds but from the underground rhizomes, which will rapidly grow them out of a container. They are gorgeous against a fence, but until they begin to bloom from August to November, they are pretty unimpressive. And if you were planning to submerge parts of the pots in the water, don't. They are not water plants, need only dry to moist soil, and their roots would drown before you ever got the chance to see the blooms. Here are some pictures from the Image Archive of Central Texas Plants of various stages and parts of this plant. If you are really interested in planting in your stock tane, go to our Special Collection, Wetland Plants for Central Texas. And a couple of our How-To Articles that also deal with this situation are Container Gardening with Native Plants and Water Gardening.

From our Native Plant Image Gallery:

Helianthus maximiliani

Helianthus maximiliani

Helianthus maximiliani

Helianthus maximiliani