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Wednesday - July 02, 2008

From: Fort Worth, TX
Region: Southwest
Topic: Container Gardens, Soils, Shade Tolerant, Shrubs
Title: Darkened leaves on blueberry bush
Answered by: Barbara Medford

QUESTION:

I have a blueberry bush planted in a very large pot. It has been doing very well, producing berries and new growth. All of a sudden the leaves have begun to turn dark. I have it potted in good soil and good light, but wonder if I have been watering it too much. Can you help me?

ANSWER:

This is probably a hybrid blueberry bush, with who knows what parentage, but we will work with what we know about two blueberries native to Texas and try to deduce from that what is causing your leaves to darken.

Vaccinium fuscatum (black highbush blueberry) and Vaccinium corymbosum (highbush blueberry) are both native to Texas. The USDA Plant Profile for the black highbush shows it growing naturally in only a few counties in far East Texas. The highbush blueberry, in this USDA Plant Profile, grows in a few more Texas counties, but they are all in deep east and northeast Texas. This is probably our best clue to what's going on with your blueberries. East Texas is well known to have acid, sandy soils, rich in organic matter because of the stands of trees, including pines in that area. Fort Worth is well known to NOT have that kind of soil, with the soils generally being more alkaline.

You obviously made a wise choice potting your blueberry. Read this article from Botany.com on Vaccinium, and learn how to manufacture the correct soil for an acid-loving plant in an area with alkaline soils. Page down on the site until you come to paragraphs on Potting, Container Growing and Fertilizer. They will give you step-by-step instructions for planting and caring for your blueberry. The only place we found a mention of darkening leaves was in reference to a possible nitrogen deficiency. When the soil is amended, a high-nitrogen fertilizer, blood meal or cottonseed meal need to be added. According to our Native Plant Database, blueberries frequently grow in swamp areas, and need a damp soil, with good drainage. They can tolerate sun, part shade to shade; since they are more commonly found in cooler areas, it might be well to put the pot in a spot that is shaded during the hottest part of the day.

Vaccinium fuscatum