Questions on: Sunflower
Ron Smith, Horticulturist, NDSU Extension Service
Q: I have sunflowers growing on the side of my house next to the foundation. They return every year by reseeding. The plants start to grow healthy, but as they get taller, the bottom leaves turn brown and dry up. This continues until the entire plant is dead. I do get flowers, but the plants die too soon. I think there is something wrong with the soil, but I don't know what to do about it. Do you have any suggestions? (e-mail reference)
A: There are too many sunflower diseases to single one out. The diseases include alternara, white mold, rust and more. I wouldn't keep the sunflowers in that spot any longer. Move the plants to a location that gets full sun and air circulation. If that is the only spot you can grow the sunflowers, apply a general fungicide every 10 to 14 days as they grow.
Q: I have a question about sunflower seeds that I hope you can help me with. I planted sunflowers this past summer. Can I eat the seeds right off the flower or do I have to cook the seeds? (e-mail reference)
A: Some aficionados claim you get better nutrition and health benefits from raw seed consumption over the cooked.
Q. Can you tell me what is wrong with my sunflower and squash leaves? They seem to have a grayish discoloration. I also bought what I thought was a kobold blue liatris, but it looks like a garden weed. Is this what it should look like? (Moorhead, Minn.)
A. Both plants have a bad case of downy mildew, and the weed is giant foxtail. Spray plants with Daconil in the spring to prevent onset of the disease, and repeat monthly. Control the weed with a preemergent herbicide.
Q. We have a problem with the enclosed sunflower plants. They have started to curl up some and have a firmer, drier texture compared to the normal soft-leaved plants. They are located on the edge of a field next to canola that has been sprayed with some type of chemical. Can you tell us what kind of chemical would cause this and will we still have a crop? (New Rockford, N.D.)
A. There is no doubt your sunflowers were hit with a broadleaf herbicide spray, most likely a phenoxy type like 2,4-D or MCPP. On the samples you sent, the damage appeared extensive, and may cause the plants to not flower properly, or be unable to get seed.
I hope this visual diagnosis helps. To get specific about which phenoxy was used, a chemical lab analysis, likely using a chromatograph, would be necessary. The cost would be approximately $250 per test.
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