Verbesina are generally easily distinguished from most other plants on Kure based on broad serrated leaves (saw-toothed), an ascending stem, and orange-yellow flowers. In mature stands, Verbesina can reach heights of 7-8 feet, but you can also find mature plants as small as 3 inches tall. Few other plants on Kure have broad leaves and most can be readily distinguished from Verbesina.
If you take away the scale, the three leaves below look very similar (From left to right: Verbesina, Solanum, Chenopodium). Once you notice the watch buckle in the 1st and 3rd photos and the thumb in the 2nd, the small sizes of the leaves below is a clue. Other distinguishing characteristics are the rounded teeth and flanged stem in the Solanum, and the irregular teeth in the Chenopodium.
At the cotyledon stage, it can be difficult to distinguish Verbesina from Lobularia maritima. Verbesina at this age often shows a white or light leaf margin. A more reliable characteristic, however, is the shape at the base of the leaf. Verbesina leaves taper gradually to the stem, compared to Lobularia, which is rounded off before the stem. In the picture at the lower left, several Verbesina are joined by a single Lobularia (second from right). Note the shape of the base of the leaves comparing the leftmost plant with the Lobularia. The picture below right shows Verbesina on the left.
The first true leaves begin to show the characteristic serrated (saw-toothed) leaf margin (edge) and are broad, compared to a long slender second pair of leaves on Lobularia. Though difficult, the first true leaves on Verbesina are pubescent, bearing stiff white hairs.
Leaf shape and color in young plants is highly variable based on conditions, with color ranging from dark green nearly to yellow, and from oblong to spoon-shaped. Both Verbesina and Lobularia are pubescent, or hairy, a trait that is apparent from the first true leaves on, but the hairs on Verbesina are coarser and more readily visible. The hairs on Lobularia, also white, are appressed (lying flat) and give the leaves a soft whitish-green appearance.
Leaf characteristics can also differ substantially in larger plants. In the two examples below the number, size, and sharpness of the teeth are dramatically different, but in both cases, these can be identified as Verbesina due to the lack of a flange on the stem.
Description: Taprooted annual herbs; stems 2-10 dm long, many-branched. Leaves opposite, upper ones alternate, ovate or deltate, 4-15 cm long, 2-10 cm wide, both surfaces canescent-strigoese, sometimes less so on upper surface4, margins coarsely and often irregularly serrate, petioles dilated at the base to form a pair of stipule-like auricles. Heads solitary at the ends of long peduncles or in clusters of 2-3, radiate; involucral bracts ca. 15, green, subequal, linear, 7-15 mm long; ray florets 10-15 per head, pistillate, rays bright yellow, 10-25 mm long; disk florets numerous, corollas yellow, ca. 8 mm long. Achenes winged (Wagner et al., 1999; p. 372).