Wood mulch works well around fruit trees

Q: Please provide me with recommendations for types of mulch for fruit trees.

A: By definition, mulches lay on top of the soil surface and are not mixed with the soil. There are organic mulches such as wood chips and there are inorganic mulches such as rock and plastic. Most mulches shade the soil surface, help to conserve water and reduce weed problems.

Mulches made from wood decompose over time as long as moisture is present. Decomposing wood mulch enriches the soil. Rock and bark mulches do not. Their purpose is primarily to add beauty and reduce weed problems.

Any wood mulch, not bark mulch, works well around fruit trees. The best kind is a mixture of different types of wood and decomposes in two to three years. You don’t want to use only bark mulch if your purpose is soil improvement.

Decaying wood does take nitrogen from the soil but this is not a problem as long as trees and shrubs are fertilized annually.

Some of the best mulches for fruit trees are wood chips from a variety of trees but excluding trees with long thorns such as many of the mesquite trees, athel and salt cedar and palms. Palm trimmings decompose very slowly. Wood chips from trees with long thorns end up puncturing the bottom of a sneaker or vehicle tires.

Just about any wood source will pose no problems, including eucalyptus, cedar and even oleander. An excellent mulch is also the residue left behind from stump grinders.

Q: I dug up some of our native soil and amended it with 50 percent planting mix. The next day after it dried, this white substance appeared on the surface. Is this salt or alkali? I know my soil will effervesce when you pour vinegar over it.

A: Salt and alkali are pretty much the same thing. Alkali should not be confused with alkaline. Alkaline refers to pH. Alkali refers to salts. Soils that create bubbles or effervesce when vinegar is applied to them have quite a bit of calcium carbonate, or lime present.

The old-timers who grew things in desert soils would refer to “white alkali” and “black alkali.” I think the word “alkali” has remained in our vocabulary, but not the difference between white and black types, and it is just as confusing now as it was then.

Although alkali refers to the white salt accumulation on the top of soils. These white salts were usually sodium sulfate, sodium chloride and magnesium sulfate.

Black alkali on the other hand left blackish spots on the soil surface usually composed of sodium carbonate and organic matter. It was understood that black alkali was more damaging to plants in soils than white alkali.

When ranking these salts and their injurious effects on crops, sodium carbonate was considered the worst while sodium chloride (table salt) was somewhere in the middle and sodium sulfate the least injurious. When you had black alkali salts, many farmers would just give up and walk away from those soils.

The salts in your picture look like white alkali. I would have to guess it is a mixture of salts containing calcium, sodium and magnesium and carbonates, sulfates and chlorides. You wouldn’t know unless you submitted the soil for a soil test.

When salts accumulate on the soil surface it is best to take a flat-nosed shovel and scrape off the top inch or so and dispose of it. Then begin activities that reduce the salt content.

Most salts are removed with water and flushing. Level the soil surface as much as possible. Sprinkle the soil with water to push the remaining salts deeper into the soil. The idea is to push the salts deeper than the roots of your crops.

If the soil does not drain easily, there may be a high sodium problem. If this is the case, apply gypsum to the top of the soil and rake or rototill it in as deep as you can. Then begin your irrigations.

Gypsum is used to remove sodium from the soil and replace it with calcium. Sodium is a bad player in soils and prevents drainage. Substituting calcium for sodium improves drainage. Also, mixing compost in the soil will help in the removal of salts and make them less injurious to plants.

Q: We have a very old globe mallow shrub that looks bad after a frost. When and how should it be pruned to bring it back to its former glory? Does Mexican red bird of paradise need regular pruning? How can one tell what and where to cut?

A: If the globe mallow is looking kind of old and ratty you can cut it down to an inch of the soil and totally renew it or you can selectively cut down some of the older stems and renew it slowly.

If you want to keep it bushy from head to toe then take about one third of the oldest wood out now, next year take another third and the following year take another third. This will renew it over a three-year cycle and help keep the foliage and flowers from top to bottom.

You would do this pruning in the winter months or immediately after it finishes flowering.

Mexican red bird of paradise usually gets a pruning to the ground every few years because of hard freezes. You have a couple of choices, much like your globe mallow. You can cut it to the ground or selectively remove one third of the oldest wood to the ground and in a three-year cycle.

You would do this pruning during the winter months or before new growth starts in the spring or after flowering is finished.

Q: I recently purchased tulips already in a container and they bloomed for almost 10 days. The roots were sitting in water, and I had to add a little each time so their roots reached the water. How can I save the bulbs for later planting next year? Can I keep them cold all year until next year?

A: This is the beginning of February and you are not too late to plant now if you are able. Could you plant them in some containers and enjoy them that way rather than planting them in the ground?

When tulips bloom, they are exhausted. They consume a lot of energy stored in the bulb to push the leaves and flower out. They need many weeks or months after that to rebuild that corm to its original size or even larger.

So after bloom the leaves must remain attached to the plant while they rebuild the corm. Once the corm has rebuilt its size, everything green could be cut back and slipped back into the refrigerator for six weeks. They can then be repotted again and forced to bloom.

You can repeat this cycle several times as long as they rebuild the corms each time and receive eight weeks of chilling in the refrigerator. You can do this to nearly any spring flowering bulb.

It would be very difficult to keep them for a year in a refrigerator or even specialized containers for that length of time primarily because of storage diseases. It should not stop you from trying it, though. They will bloom again as long as they have about six weeks of cold temperatures. Give it a try.

Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com. Send questions to extremehort@aol.com.