Wisteria leaves turning yellow

[green.willow]

Last summer I planted a rather large wisteria. It flourished. I live in the high desert, so it got a couple of gallons of water twice a week, all winter and once it stated leafing out, I turned on the watering system. Started out looking good, but now the leaves are all yellowing. I'm at a loss, other than I'm pretty sure it getting plenty of water as everything else on that leg of the system is doing fine. Ideas?

 

[DirtMechanic]

From UC:

"High Desert soils are mostly loamy sand, deep and well-drained Entisols* formed in alluvium fans derived dominantly from granitic rocks and related rocks."

Typical Entisol Profile

These soils have very low organic matter, are high in potassium and have pH's around 7.5 to 8.0. A saline and/or alkaline surface layer occurs in places."

Does that sound like your soil? Wisteria like a mildly acidic soil. Do you know which wisteria you have? Are the pods smooth (american) or (asian)? Do flowers come before the leaf out (asian) or after leaf out (american)? Is plenty of water more than one inch per week or less?

"Average seasonal foliar displays aside, why do wisteria leaves turn yellow in the growing season? One of the main reasons may be an iron deficiency in the soil. An easy to find soil kit can give you the answer. If iron is deficient, roots have trouble taking up nutrients. Wisteria enjoy neutral to slightly acidic soil. The lack of iron in soil will create a soil pH that is too alkaline. This is easy to amend with the addition of compost or peat. Another possible issue is poor drainage. Overly boggy, soggy soil is not a condition that a wisteria will put up with and that excess moisture will manifest in limp, yellowing leaves that will start to fall off the plant. Check your drainage and stop watering until you can maintain proper porosity."

Read more at Gardening Know How: Wisteria Leaf Problems: What To Do For A Wisteria With Yellow Leaves https://www.gardeningknowhow.com/ornamental/vines/wisteria/wisteria-with-yellow-leaves.htm

And always, clear pictures of both context and closeups are most helpful.

 

[green.willow]

I believe it's an Asian. Yes, that would be my soil. I just now tested it. High PH (7.5) High Phosphorus. High Potash. Depleted nitrogen. I have some high Nitrogen fertilizer on hand but it it 22-8-8. Do you think that will be okay, or should I hunt down something with no P and K?

 

[DirtMechanic]

Actually, a measure of P has 2 parts, available and present but not useable. Let me share some graphs related to the power of acids and bases to dissolve or otherwise lock up resources you think you have, but in actuality cannot access.

This idea is true of K as well. The pH preference of the plant is more important than one might understand initially due to availability. Calcium Nitrate might be a good fertilizer, with an iron kicker. Azomite and some other broad micronutrient supply come to mind. Calcium nitrate is one of the only water soluble, readily usable forms of calcium you can find.

The thing is, I am in a completely opposite environment from you. There will be a few, 1, 2, or 3 of the more respected nursuries or plant sellers in your area, and you should seek their council.

 

[green.willow]

Thank you so much! Good nurseries are hard to find around here. I will call one I like in Albuquerque and make a trip up there if the have Calcium nitrate. I will also look into micronutrients. Very much appreciate your help. I will pick up some peat tomorrow to try to lower the PH a bit, as well.