Black Sunflower leaves
The leaves on my firecracker sunflower are turning black around the edges and are very brittle. The black appears to start around the edges and then work it’s way toward the center of the leaf. I have applied an organic fungicide but it appears to be ineffective. I really would appreciate any ideas you might have. Thank you.
Lane County Oregon sunflowers
Thank you for your question. Are you able to take and send photos of the leaves, both closeup and from a distance? Thanks!
Thank you! There are two potential causes identified in Extension literature. The first is sunburn, described here: https://pnwhandbooks.org/plantdisease/host-disease/sunflower-helianthus-spp-sunburn The second is a phosphorus deficiency (the ‘P’ in the N-P-K on fertilizer containers, such as 10-10-10). Since I don’t know whether your plant is in full sun, your watering habits, or the soil nutrients, none can be ruled out. But, since it is an annual, it will be an issue for only a short time longer, and none of these will kill it prematurely. Thanks for using Ask an Expert!
Thank you for your help. My sunflowers are in full sun so I water every morning (on hot days) and every other day on cooler days. I will check out the potassium levels.