Ozark sunflower

Sunflowers are in the Asteraceae family and Helianthus genus. Helianthus is derived from the Latin “helios” (sun) and “anthos” (flower). The epithet, “silphioides” means “looks like silphium” which is another genus in the Asteraceae family. It does look a bit like another wildflower I find on Ozark Edge- Silphium integrifolium. Common names include Silphium sunflower, Rosinweed sunflower and, my favorite, Ozark sunflower. Its peak occurrence is within the Ozark mountains of Arkansas.

Buds appear at the top of the plant in late July and early August. The large flowers of Helianthus silphioides are about 2-3 " in width. They are butterscotch yellow with a dark, redish central disk. At the base of each flower, layered green bracts lay flat to the stem. Each plant sends up a nearly bare stem that branches numerous times toward the top to give rise to 12 or more flowers.

Helianthus silphioides is later to bloom than Helianthus mollis, usually waiting until late August to fully open. Peak bloom typically occurs in September and ends by early October.

Ozark sunflowers are perennial native wildflowers growing to a height of 6 feet or more. They have distinctive leaves that occur opposite on the lower aspect of the plant and alternate on the upper part. The beautiful lower leaves are much larger than the sparse upper leaves. They have a somewhat oval shape and are rough to the touch. Rubbing ones hand against the leaves is similar to rubbing against sandpaper. The edges of the leaves are toothed. They have a tendency to fold longitudinally along the prominent vein. On the upper portion of the stem, the alternate leaves are more widely spaced and smaller. The photos below show leaves from the top to the lower part of the plant.

The stem tends to have bristly hairs on the lower aspect and may be nearly hairless on the top half of the plant.

Seed dispersal of Helianthus silphioides is thought to be limited without human or animal intervention. The seeds are not dispersed by wind and are more likely to fall and stay under the maternal plant. Little is known about the life history of this plant. Deer and other mammals eat the achenes (one-seeded fruit with thin wall) which may help in seed dispersal. Birds may also assist in spreading the plants.

Very little is known or documented regarding the pollinators of this beautiful native wildflower. I've recorded and photographed Monarch butterflies visiting the flowers. They are beautiful next to the bright yellow of the flowers.

Other insect visitors I've documented include Drone flies, Pearl crescent butterflies, Sachem skippers and many Soldier beetles.

Across its limited range, Helianthus silphioides doesn’t seem to be too picky about its habitat. It is reported to prefer acid soil and can thrive on both dry upland sites as well as wet, sandy sites. On Ozarkedge, I find it growing at the edges of prairie/grassland habitat, preferring areas with partial shade. I also find it growing at the borders of woods or open woods and at the edges of sunny glades. In the past I've often seen Ozark sunflowers blooming beautifully along Arkansas roadsides, but sadly, that is rare now due to roadside mowing.

NaturesServe shows Helianthus silphioides as Apparently Secure, however within its range it is only shown as Secure in Mississippi! It is listed as Critically Imperiled in Illinois, Kentucky and Oklahoma and Imperiled in Tennessee and Louisiana. There is No Status Rank shown for Missouri, Arkansas and Alabama.

In Arkansas it has a C-value of 7 out of 10 (in the group of 4-7). This means "Typically matrix taxa in intact, stable habitats, with some limited ability to respond to destabilizing forces and repopulate areas from which they have been extirpated.".

There are many potential threats to the long term viability of Helianthus silphioides. Much of its preferred habitat is being lost to pine plantations, agriculture, development and roadside mowing. Exotic plant species such as kudzu, Japanese honeysuckle and many others encroach on the remaining habitat. Since Helianthus silphioides is such a showy species, it has also lost ground to collection from gardening enthusiasts and seed companies who dig the plants for their own purposes.

Some years I find red aphids on the Ozark sunflowers . They appear suddenly when the plants bloom and can cover many stems. Aphids are not uncommon on sunflowers. Surrounding plants seem to be ignored by the intruders. Fortunately, the aphid attack doesn’t seem to adversely affect Helianthus silphioides. I assume it is part of nature’s cycle.

Certainly the praying mantis I photographed below enjoyed the feast.