Yesterday I happened to notice that of the six Tithonia Mexican sunflowers I planted, one is definitely different. Five have a rather open habit with orange flowers. The sixth one (on the left) is pretty vertical and more dense with leaves that are a lot larger.
Some internet sleuthing turned up some help in identification. There are two genera of Tithonia. What is usually sold as Mexican Sunflower or Torch Flower is Tithonia rotundifolia that has orange flowers and can get 4-6’ tall.
However, Tithonia diversifolia has a woody stem, yellow flowers and can get 6-9’ tall! That might be what the sixth plant is:
What I found most interesting is that the diversifolia can be used as a green fertilizer either by mulching with it or burying it because it has the ability to make fertilizer in the soil. Used as a fertilizer, this Tithonia’s NPK is 1.76% N, 0.82% P and 3.92% K.
If those flower buds open to yellow flowers, the mystery might be solved.