Blueberry Leaf Issue

Asked August 21, 2020, 3:22 PM EDT

I have a couple of blueberry bushes in my backyard and recently have noticed the leaves are showing burning or stress. The internet points to a potassium deficiency but wondering if it could also be lack of water during our hot period? Some info. says you need a tissue sampling to be sure?

Polk County Oregon

1 Response

Hi and thanks for contacting Ask an Expert.
This looks like sunburn. Many, many plant pix have been sent in with the crispy browning edges that are sunburned leaves. A few questions though.
Is this type of leaf showing all the way around the plants? Or just on one side? Are they shaded at all? Do you have them mulched or have a drip irrigation system for them.
You are correct that the plants need adequate and steady water supply. That doesn't mean water them constantly but enough to make sure the soil is moist. Water deeply at 3-4 days in this heat but check with your finger to see if the soil is still moist (down to the second knuckle). A great mulch for blueberries is sawdust and peat moss. Both will help the soil stay acidic.
If the damage is all on one side, could it be herbicide drift?
A temporary shade cloth cover will help the plants along with the mulch and water schedule I suggested.
Here is a link on blueberries grown in the home garden: https://catalog.extension.oregonstate.edu/ec1304/html
Potassium deficiency is relatively rare in Oregon. Leaves of K-deficient plants may develop several symptoms, including scorching along the margin, cupping, curling, and necrotic spots. Low leaf K values may be caused by poor drainage, drought, or very acid soils. I do not see any necrotic spots or curling on the leaves. If you want to do a tissue sample normal August leaf K levels are 0.41 to 0.70 percent.
Typical sources of potassium include mined rock powders and wood ash. Of course, manures, compost and other organic materials are potassium sources too. A mulch that includes composted manure will add potassium slowly and at low levels.
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