Heliopsis vs. Helianthus (Indiana)
I have noticed that Heliopsis helianthoides observations on iNat often get ID'd to Helianthus, especially by the computer vision. It's getting more accurate but I still want to express how I quickly discern them in the field. When a Heliopsis is observed, the most common incorrect ID's that I see from the computer vision are some of the woodland sunflowers (Helianthus decapetalus, Helianthus strumosus and Helianthus divaricatus).
The easiest difference is that Heliopsis has phyllaries that come to a blunt tip, while Helianthus has "spiky" involucres consisting of sharp-tipped bracts. The flower buds of Heliopsis are quite urn-shaped just before opening. The technical difference between Heliopsis and Helianthoides is that Heliopsis has fertile ray florets but Helianthus has sterile ones.
Heliopsis involucre:
https://www.inaturalist.org/observations/86352061 | https://www.inaturalist.org/observations/85402033
Assorted Helianthus involucre:
https://www.inaturalist.org/observations/94454703 | https://www.inaturalist.org/observations/90899588 | https://www.inaturalist.org/observations/86586799
In each photo, the Heliopsis are on the left, Helianthus is on the right. https://www.inaturalist.org/observations/237021501
Other features that I have noticed are that Heliopsis usually grows with the inflorescence facing straight up, perpendicular to the horizon, while the woodland Helianthus usually have nodding heads that want to face the horizon. Heliopsis often has slightly more orange rays than the woodland sunflowers, but meager individuals can be paler yellow.
Both Heliopsis helianthoides and Helianthus spp are sunflowers that tolerate a wide range of habitat preferences. Heliopsis can grow in shade or sun, in moist to slightly dry ground. Heliopsis helianthoides is also the host plant of Lygaeus turcicus, a bug that resembles the large milkweed bug. Red goldenrod aphids of the genus Uroleucon can also be abundant on the stems of Heliopsis, but I wouldn't be surprised if they also feed on Helianthus. Of the three woodland sunflowers mentioned before, H. divaricatus seems to be most adapted to open or savannah areas, the others are typically found in woods. Heliopsis is often used in restoration plantings because it has high germination rates and will often flower the first summer after planting. I will say that the plants that I see in restorations are often quite a bit more vigorous than populations that I believe to be wild, and often have more pronounced inner phyllaries. I attribute this to the affects of breeding plants at an industrial scale--the more vigorous plants may produce more seed. Indeed, Heliopsis helianthoides is quite variable and this fact no doubt accounts for the low accuracy of iNat's computer vision.
Last edited 8-21-2024
