PlantFiles: Maximillian Sunflower, Prairie Sunflower
Helianthus maximilianii

After 3 years, a single plug has grown to a 2-foot clump that produces over a dozen stems. It is in rich soil in full sun and grows about 12' high. This year I cut it down to about 9' late in the season because it was flopping over despite being tied to a 4' fence. The shape of the plant was much improved by this pruning and I intend to do it again next year, but earlier and more often to keep it at 9' and hopefully encourage fuller growth.

The "branches" that emerge from the main stems are about 3-4' long and covered with leaves and flowers from base to tip. These branches have a tendency to snap at the base if birds land on them or they get heavy from flowers. I remove them (and put them in a vase) to maintain the elegant shape of the plant.

We enjoy the privacy afforded by this tall and fast-growing flower. I'm surprised that others don't use it more. I haven't seen any others in my town, only a few scattered at farms and fields in my area. With its graceful stems and palm-frond leaves, this is a very beautiful plant.

This blooms very late in the season here in zone 6b, with the asters and mums.

Further to comment by straea:
Have grown this plant in three different perennial beds (all upgraded clay). I was actually assured by the nursery that it was not invasive. After two or three year it was advancing through the beds, in one case into the lawn and in another into an ornamental pine. It was so shallow rooted that removing all of it was quite easy. I now use clump-forming Heliopsis helianthoides (false sunflower) cultivars instead.

It was only after I planted this that I first heard about its potentially aggressive tendencies. Guess I didn't do enough research. Regardless, last year (its first year), planted in early summer from a good-sized but not huge container, it bloomed in a small clump on tall, wiry stems that didn't shade its neighbors as much as one might think from a tall plant. I enjoyed the pretty blooms and then birds enjoyed the seeds. Apparently it was expending most of its energy on its roots last year, because this year it came up in a clump over twice the size of last year's and has been spreading its roots outward over the past two months, sending up new sprouts as it goes. I wouldn't have planted it close to my Oriental poppies if I had known how aggressive it can be (and this is poor, dry soil, not its preferred good soil) and would recommend using it in a spot where its creeping root system would be a benefit rather than a potential drawback. By the way, my garden is very windy and it's in one of the windiest spots of all, and it didn't need staking, though it did tend to tilt its bloom stalks somewhat as it bloomed (which I personally thought added to its charm). I don't know if it adapts to frequently windy sites or what.

Their first year, they grew to about ten feet tall. Problem was they were not bushy so they looked scraggly with blooms only near the top. Should I pinch them?
Compared to a hybrid named Marc's Apollo growing next to them that was bushy, prolific and bloomed to the end of November, they were kind of sad. One more year of scraggly growth and they get yanked for more Apollos

Perennial sunflowers! Who can resist?

They're great in the late summer/fall. The first season (2001), they grew 6-8 feet but have been growing progressively smaller each subsequent season. Probably poor soil or something: my soil is heavy-ish clay with little nitrogen, and I don't have the energy to enrich.

They do self-seed vigorously, but the seedlings are easy to identify and pull out. Compared to chinese elm seedlings, these are no sweat.

Zone 8b, Southeast, TX in Broaddus:
In March, I found a 3" tall seedling under my bird feeder. Tom fills bird feeder with sunflower seeds.
I transplanted seedling to full-sun area in March -06. I placed a 6' tomato cage over it while small. Today, May 23-06 my Maximiliani Sunflower is 5' tall and has one bloom 4" across.

It's a keeper, and free!

Hopefully this won't be too invasive because I love it and so do the finches. They blend in with it so well that you really have to look close to see them. As the flowers loose the yellow and turn brown in the fall, so do the finches! They do have a tendency to flop (the plant, not the finches).

Use Maximaillian sunflower extremely sparingly in new plantings, particularly on good soil. It is very aggressive and will dominate a planting.

Striking plant to have in the garden! Three inch wide blooms stacked one above another on three feet of stalk.

The Maximillian sunflower is really beautiful in the Fall together with golden rod, purple and white asters, and orange butterfly weed.
They do require tying but it is very much worth it.

I was disappointed at first since there were no blooms all summer and the plants became quite large and were shading out some other plants in the same bed. Then in the fall they were covered with six inch blooms when not much else was blooming. I have since moved them to another spot where they will not shade out other plants and there is a fence behind them which I use to tie them up with a string since the heads are very heavy and they tend to fall over. There are so many blooms they are also good for cutting for indoor arrangements in fall colors.

Helianthus maximilianii is sometimes sold as a perennial. I started seed and now have transplanted about 30 seedlings, all of them now (mid-July) 12"+ and growing, vigorous,with long arching leaves. All are clearly related but have the sunflower trait of variations on a common theme.

No flowers have appeared; the catalog described this plant as a kind of flowering hedge. That's what I hope for!

Common Name: Prairie Sunflower

Very robust 6' to 8' plants, producing large quantities of single yellow blooms in late summer.