Helianthus spp. at Knoxville, TN Garden Center

I thank the person who gave me a native swamp sunflower (Helianthus angustifolia). This long-lived perennial appears to have its own internal clock for blooming around the first day of October. Its long narrow rough-textured leaves average 6 inches in length. The 2-3 inch wide flowers appear first on top of the tall 6 to 7  foot plants, and numerous floral side branches soon follow.

Fall sunflowers are best grown in full sun to insure shorter sturdier plants which need no staking. Plants growing in partially shaded sites do not branch well and produce fewer flowers.  If you have no room for 6-10 foot plants, cut them back by half once or twice before the mid- August. Pruning improves branching.

Swamp sunflowers are abit hoggish when it comes to soil moisture. Established plants possess moderate drought and great heat tolerances. Do not fertilize fall sunflowers as they are voracious feeders and tend to need staking, a chore I like to avoid.

In ten years plants have never become invasive in my garden.  I suspect the late flowers have not enough time to mature viable seeds. Two other fall sunflowers to select for your fall garden are 18- inch tall ‘Lowdown’ willowleaf (H. salicifolius ‘Lowdown’) and 6-8 foot tall Helianthus x ‘Lemon Lady’.

Helianthus spp. are winter hardy in the Southern Appalachian region (USDA zones 6 and 7). Plant fall sunflowers from March thru July so that plant roots have adequate time to become well anchored and survive the winter cold.