Issue: July 19, 1999

Rock landscape isn't xeriscape

Why are so many people changing their landscapes to rocks? I know it conserves water, but doesn't it make it a lot hotter? A rock landscape isn't a xeriscape, is it?

People are trying to conserve water by changing their landscapes to rock landscapes. Like many others, they are exhibiting a growing awareness of the limited water available in New Mexico. They are probably also responding to the increasing water rates and public education regarding the water issue. You are correct in suggesting that a rock landscape is hotter than a landscape with plants.

You are also correct in your statement that rock landscapes are not considered xeriscapes by many horticulturists and proponents of xeriscape. Rock landscapes do reduce landscape water use, but the savings in water is not as great as some people think because water used in evaporative coolers is increased.

Rocks can be an important part of a true xeriscape which reduces water use, but not at the expense of the beautiful landscape. Rocks are an excellent mulch material to use around plants native to hot, dry environments. Plants native to cooler, moister parts of the world may have difficulty surviving the heat that is common in rock mulches in the summer in New Mexico. Plants native to cooler environments do better with an organic mulch.

For those plants that will tolerate the heat of rock mulch, and there are a very large number of such plants, the rocks reduce weed competition and evaporation of water. Beneath the mulch the temperatures are also lower.

If the rock mulch is to be effective in reducing weed growth, it should be three to four inches thick. Weed barrier fabrics, those which are permeable to oxygen and water, may be used under the rock mulch, but are not always necessary. This same thickness of mulch reduces evaporation by cooling the soil beneath the mulch and by keeping the wind and sunlight away from moist soil.

If you have read my gardening column before, you know that I prefer a landscape with a lot of plants. The plants, though they do use some water, cool the environment and create beauty and are worth the extra water that they consume, especially if they are plants adapted to low water conditions.

What to do with old rotting globe willow

My globe willow tree is about 30 years old and beginning to have a lot of large dead branches (picture enclosed). There are also mushrooms growing on the trunk. What can I do to save the tree?

A globe willow tree in the condition you described and at that age is probably beyond saving. The photos you sent confirm that conclusion.

The globe willow does not live to be hundreds of years old. Thirty years is a long time for a globe willow. Yes, there are some that live longer, but there are many more that don't live as long.

The dead branches showing in the picture are above electrical lines and are quite large. They are a hazard to your electrical service and to people standing under them. The dead branches certainly should be removed.

The presence of mushrooms growing on the trunk indicates that the trunk is also rotting. This is not safe and, since the tree is leaning, creates a great hazard.

The best solution is to remove the tree. This is best accomplished by a professional in the tree care business who is insured and has the proper equipment. It is important that people, structures, and the electrical service be protected as the tree is removed.