Yellowing leaves on sunflowers

Question: Just curious about the possible cause of the yellowing leaves on some of my sunflowers. These are "volunteers" from seed dropped last year. They are growing in full sun in my pollinator garden. There are about a dozen or so plants here & there about 6-8" high but these are the only ones showing this sort of leaf variegation. Thanks!

responder: Barb  Replied May 30, 2023, 9:03 PM EDT
response: Hi,  I assume you touched the splotches to make sure they didn't come off and weren't something dropped by another plant (like sap?) or animal?  And did you check underneath for insects?   I don't actually think they look like disease or insect or deficiency for two reasons.  One is that it's so uncommon, occurring on only a few of the leaves of all the dozen or so plants you have.  The other is that the shape is not what is commonly seen with a nutrient deficiency, insect or disease.  The yellow blotches are quite irregular.  That said, I don't know what it is.  Please let me know if it spreads or if that is the extent of it.  If it spreads or you have any new data, let me know and I'll try to find a plant pathologist for more help.

responder: The Question Asker Replied June 01, 2023, 11:25 AM EDT
response: Yes – I touched the leaves; the coloring is part of the leaf itself, not something dropped/spilled on it. No sign of insects or other pests; the leaf is smooth, no raised bumps or other odd texture. I took a picture of the reverse side of the largest leaf yesterday: Maybe a mutation has created a new variety --   a variegated-leaf sunflower! HAHAThese sunflowers, by the way, are a third-generation batch that grew from volunteers that came up a few years ago from dropped seed that came up the following spring from seeds fallen from the multi-branched, lower-growing hybrid sunflowers I had planted. I simply dug up some of those volunteers and replanted a number of the seedlings where I wanted them - knowing I would get an assortment of sizes/colors/types since the first-year seeds were a hybrid variety.  But I was not particular as to what they looked like. Since then I just let the seeds fall where they may and thin out the plants to as many as I want.By the way – this is in the “Bookworm Garden” that I planted some years ago at our county library. Thought you might like a couple of pictures from a couple of years ago, each from a different corner of the bed. Note that I’ve registered it as a Monarch Waystation with MonarchWatch. Also, it has evolved since these photos were taken in late July 2021 because over the last 4 years I have been transitioning it from the herb garden it was originally, so there are now more native plants and fewer herb plants.       Here are views from the same angles as above taken yesterday:  Although they are not native, I left the large patch of thyme and allow the self-sowing alyssum to appear each year since they attract a multitude of tiny pollinators early. I also scatter Verbena bonariensis plants through the patch since they attract many species – and last fall a lot of migrating Painted Ladies were dropping by for them! There are daffodils planted around the mailbox (it’s not used for anything, just decoration from the early days) for early spring color.  There’s also rose campion (from my yard!) although it’s a Eurasian plant - but its bright magenta flowers are beautiful and it’s not hard to keep from being invasive thanks to its distinctive foliage. Here is what the space looked like from the street about 8 years ago!   Sorry to take so much of your time rambling on about the garden. You really needn’t pursue this further; if the plants succumb there are others to fill in! I mostly am just curious since I never had seen mottling like it in all my decades of gardening. Thanks, Barb!CarolSent from Mail for Windows From: Ask ExtensionSent: Tuesday, May 30, 2023 9:03 PMTo: botanygal47Subject: Re: Yellowing leaves on sunflowers (#0102410)

responder: Barb  Replied June 02, 2023, 4:23 PM EDT
response: Hi, I wonder if it is a weird genetic thing from the hybrid flowers since it's actually seemingly in the plant but not really damage.  It would be interesting to keep seeds from those yellow-leaf plants and see what they do next year. Thank you for sharing photos of your Bookworm Garden!  It is gorgeous and I can appreciate the work that has gone into it - first, creating it and then maintaining it.  And what an improvement, too, aside from the benefit to nature!  I also maintain a large perennial garden so I am familiar with both V. bonariensis and rose campion, the latter of which never lasted very long for me. Happy gardening and thanks again, Barb

responder: The Question Asker Replied June 03, 2023, 6:56 AM EDT
response: That’s what I was thinking – where are Mendel or Darwin when you need them… LOL I’ll keep some of the seeds (if the local goldfinches allow it!), but since the plant is not isolated from the rest, I expect the odds are pretty slim that I’d get a repeat performance next year. Thanks for the nice words about the Bookworm Garden! If you are in Marion sometime, stop by the library. Rose campion is a short-lived perennial, but as you know produces a LOT of seeds! After enjoying your plants for 3-4 years, save some seed – although you should get enough volunteers in the spring that you could watch for & save a few of those each year for a continuing supply.  Thanks again for your thoughts, Barb! All the best, Carol (“Retired” Penn State Master Gardener) Sent from Mail for Windows From: Ask ExtensionSent: Friday, June 2, 2023 4:23 PMTo: botanygal47Subject: Re: Yellowing leaves on sunflowers (#0102410)

responder: Barb  Replied June 04, 2023, 1:37 PM EDT
response: If I'm ever in Marion, I will definitely try to stop by. I grabbed a plant labeled Lychnis last year at a plant swap and I think it is rose campion.  If so, I'll remember to keep some seeds just in case. I've enjoyed your emails. Take care,