Hi,

I can't figure out what's causing my zinnias to have yellow new growth. I water daily but don't think it's overwatering. I'm concerned it's a disease. If it's a nutrient deficiency, can you figure out what it is just by looking at this leaf?

Hi & welcome! What is that spot? A pot, or plastic-covered ground?

It's biodegradeable mulch. The plant is in a field.

I'm not familiar with growing Zinnias in mulch but I suspect that might be the problem.

I can't figure out that pic. Looks like black plastic on the soil, but what are those white lines? A photo from a different perspective might help.

Those leaves look pretty healthy. Normally yellow leaves are a sign of some nutritional imbalance or deficiency, but zinnas rarely need (in fact don't like) much fertilizer. Could just be from brief low temps. Can you tell us about the growing conditions?

Zoe, that's cut flower netting. They are growing cut flowers like this:
https://www.harrisseeds.com/pr...
https://www.floretflowers.com/...

It could be a lack of an immobile nutrient (like Sulfur) in the soil. It could also be that low temperatures or a PH issue is preventing uptake of a nutrient/nutrients. Have you had the soil tested by your local extension office?

https://landresources.montana....

Interesting article, Danita. I didn't know about that. Thank you.

Yes the white string stuff is netting. I've grown them in this mulch before so I don't suspect that to be the cause. I've never had this yellow on new growth before. I'm concerned it's a disease and could kill my other plants. I'm in south Mississippi and our weather has been all over the place. No freezing conditions but it has swung from the 50s-80s since they've been planted. I have many other zinnias planted but most don't have this yellow new growth.

I didn't have it tested this year. I guess it was dumb of me not to. The only thing i did to the soil was to add leaves. It wasn't a giant amount but enough to loosen up the soil and add organic matter to my soil. It's very sandy/loamy and i need to add stuff to get it to hold moisture better. I haven't fertilized since planting. If i do, it will be with neptune's hravest as im trying to stay away from chemicals.

Could be the uneven temperatures.

In my area, yellowing new growth is a sign of iron deficiency or spotty caliche deposits with high alkalinity. I don't see disease in those pics, but I agree with Danita that a soil test might be your best move.

Your soil may be getting nutrient-depleted if you grow there every year without replenishing nutrients somehow. Sandy soil is known for leaching nutrients quickly, too. I'd get a soil test asap.