Garden Detective

How to put luster back in those red leaves

To restore vibrant color to a Japanese maple, first try adding fresh mulch around the tree.
To restore vibrant color to a Japanese maple, first try adding fresh mulch around the tree. Bigstock

Experts tackle readers’ garden questions.

Q: I purchased an 8-foot-tall, roundish-shaped Japanese maple from a local nursery. They said, “In this area, this is the only Japanese maple that will stand up to the hot, direct sun and you won’t believe the fall colors!” The first year, the tree leaves turned a stunning bright red. The next two years, they were just a dull burnt red color. What does the tree need to restore its bright color? More water or some nutrient?

Greg Nakamoto, Lincoln

Master gardener Anna Symkowick-Rose: The Japanese maple (Acer palmatum) is often purchased for its stunning fall color; however, some varieties are not well-suited for the hot, dry climates in the Sacramento area.

Depending on the variety, your Japanese maple may benefit from being planted in a sheltered spot that is partly shaded and protected. In addition, Japanese maples have high water needs. They like evenly moist soil with good drainage. If the tree is planted in a clay type of soil, this could be contributing to its issues.

Sometimes dull-colored leaves are a symptom of a mineral or nutrient deficiency, the most common being nitrogen and iron. Mineral deficiency can be caused by water-logged soil, root disease and nematodes (a roundworm that can cause plant diseases). To determine if the soil has a mineral deficiency, a professional lab can perform a soil analysis. For a list of soil and plant tissue laboratories, visit http://sacmg.ucanr.edu/files/229594.pdf.

Typically, landscape plants do not require fertilizer; however, they do benefit from a thick layer of mulch (three to five inches) in the form of compost or fine wood chips placed 12 to 18 inches away from the tree trunk. The mulch will help retain moisture in the soil, reduce weeds and slowly release nitrogen. The mulch should be replenished every one or two years.

If there is not mulch already around the tree, try this remedy first. If there is mulch, take some time to replenish it. A fresh layer of mulch may be all that is needed to gain back those beautiful red colors.

For more information on landscape plants, visit the University of California Integrated Pest Management website at www.ipm.ucanr.edu or call the Sacramento County Master Gardener office at the number provided below.

Anna Symkowick-Rose is a UC Cooperative Extension master gardener for Sacramento County.

Garden questions?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&g@sacbee.com. Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:

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  • Sutter, Yuba: 530-822-7515; 9 a.m.-noon Monday-Tuesday and 1-4 p.m. Thursdays
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