Blame bad pruning, rock mulch for privets’ decline
Q: I have been living here for seven years and in the past two years my privets have turned brown and lost their leaves during the months of January and February. Last year they came back, although they weren’t as full and robust as they used to be. The privets right next to them seem to do fine throughout the winter. Why are they suddenly losing all of their leaves in the winter? What can I do to save my privets and have them come back with full growth?
A: I looked at the pictures you sent and I will post them on my blog. There are two things going on that need to be corrected or the others will start looking like the bad ones as well.
You are looking at a snapshot in time. You have two problems contributing to this problem: how the plants are pruned and the continual breakdown of the soil. Both need to be addressed.
From the looks of it, these plants are pruned with a hedge shears. If you are not careful, in a few years the old, woody growth will dominate the bottom of the hedge. This old bottom growth cannot support young succulent growth. The bottom of the hedge will be “woody,” with new growth only at the top.
Hedges are supposed to be pruned like a trapezoid, with the wider base at the bottom. Or, they can be pruned individually to remove older growth . This type of pruning causes newer growth at the bottom, which supports leaves and results in plants that are full from top to bottom.
The second problem is the type of mulch you are using. Rock mulch returns nothing to the soil. Organic mulches, such as wood mulch, continually breakdown and add to soil’s “health.”
Simply applying a fertilizer without returning some sort of organic material to the soil is not adequate. As time passes, the soil becomes depleted of organic component. Without this component, many of the soil processes necessary for good plant health diminish.
Soil health diminishes to the point that the plant becomes sick or unhealthy. Unhealthy plants are more prone to winter damage than healthy plants. One sign of low-temperature damage to “unhealthy” evergreens is leaf drop.
To correct these problems you need to remove the rock mulch and put down compost, followed by coarse wood mulch. Coarse mulch, such as the kind you get from chipping and composting green waste from your yard, will not blow into your spa/pool.
Bark mulch will blow away and is not a suitable mulch for our soils. It is only decorative .
Unfortunately, the damage to your privets will not be corrected easily. However if you want to keep them, then someone will need to start pruning them properly and renewing the soil with amendments that have been depleted.
Otherwise I would just replace the plants as they go downhill and maintain a schedule of plant replacement over the years as the plants start to look ugly.
Bob Morris is a horticulture expert living in Las Vegas; he is on special assignment in Balkh Province, Afghanistan, for the University of California, Davis. Visit his blog at xtremehorticulture.blogspot.com.
