Crops Build Nutrition in Soil

QUESTION: The soil in my garden is of varying consistencies of sand and clay, all comparatively hard and sterile. I am considering planting some sort of winter ground cover in my vegetable garden, which I could then dig in. Do you have any suggestions?

M.L., Bakersfield

ANSWER: Plants grown for their nutrient and organic value that are then tilled into the soil are called cover crops, and there are many.

Various grasses are used--including cereal grasses--as are wild clovers, vetches, beans and peas. Even the common yellow mustard that now blankets our hillsides in spring was a cover crop in orchards and vineyards, though it is now considered too weedy.

As they grow, these plants accumulate nitrogen from the soil. When you dig them back into the soil, that nitrogen becomes available to the vegetables that follow, or to trees or vines already growing in an orchard. Since the plants are tilled into the soil, they also add valuable organic matter.

Some plants are much better at this than others, but seeds of true cover crops--that do well in California--are hard to find.

One excellent source is Peaceful Valley Farm Supply (P.O. Box 2209, Grass Valley, CA 95945, [916] 272-4769). It has a mix of seeds that includes wild beans, peas, vetches and oats that it recommends for homeowners called the “Green Manure Soil Builder Mix.” The company suggests sowing three to five pounds per thousand square feet; saying that it returns up to 290 pounds of nitrogen to each acre and up to 49 tons of organic matter.

It sells the mix in small amounts--five pounds minimum at 59 cents a pound--but you’ll have to buy something else from the company, because there is a $20 minimum per order.

The reason cover crops are not used by more home gardeners is obvious: You can’t grow anything else in that spot until the plants are tilled under. However, if you plan to let the vegetable garden rest for a season, fall is the time to sow many cover crops, including the mix mentioned above. They’ll grow with the rains, and in spring you can dig them under, adding fertility and tilth to the garden.

Oil Spray Should Rid Red Pine of Pesky Pests

Q: I have some pest problem on my mature red pine. The tips of the branches get black and the roots of the needles are sooted black, and eventually the limb gets brown and dies out. Is there any insecticide I can use to cure this problem?H.H., Torrance

A: Most people have probably seen sooty mold fungus on citrus, but it is also common on pines. This black fungus lives on the sugary excrement of leaf-sucking insects, which are the actual problem. On pines, these may be aphids, pine scale or even pine mealybugs.

Most vigorous trees can stand some damage, but if too many branches are yellowing and then dying, you can blast these creatures with a strong spray of water or use a commercial soap or oil spray. Do not use so-called “dormant oils” but look for oils listed as “supreme” or “superior.”

The label should say that they can be used during hot summer weather and that they can be used on conifers. SunSpray Ultra-Fine oil is one.

Scale are the most difficult to get rid of because they are protected by hard shells, and only a few parasitic wasps and ladybugs can get under (or drill through) that shell.

The defenseless new hatchlings, called “crawlers,” are your target, so you must discover when they are crawling about. Use a hand lens to spot them (they’re about the size of the period at the end of this sentence), or double-sided tape to trap them, and when you see a lot, spray with oil. Begin checking as early as February and continue into early summer.

Also make sure ants aren’t protecting the scale (the ants feed on the honey-like excrement). If they are climbing the trunk of the tree, stop them with a band of sticky gel like Tanglefoot.

Sod Needs Preparation, but Timing Isn’t Vital

Q: When is the best time of the year to have new sod put on the frontyard? The soil is hard clay. What kind of grass will stand up to the neighbors’ cats and dogs?

A.B., Long Beach

A: Unlike grass seed, sod can be installed at almost any time of the year, as long as there is a good sprinkler system to water it daily at first (or more often in hot weather). A neighbor put in a new sod lawn just weeks ago, at the height of summer, and it’s doing fine. Inland though, it is probably too hot even for sod, so from mid-September on would be a better time.

Bermuda and zoysia grasses are the exception. Since they are dormant in winter, they are usually available March through November.

You cannot, however, plant your new sod on top of that hard clay. The soil must be dug and amended, just as if you were preparing a seed bed for sowing a lawn. Most grasses need a good, improved soil, and the better the soil, the quicker the sod will root into the ground.

The answer to the second part of your question, concerning dogs and cats, is not so straightforward.

According to Bob Cohen, who has 30 years’ experience with the Green Scene, lawn and landscape installers in the San Fernando Valley, choosing a type of grass that works in your environment is more important.

First decide if your lawn area is sunny or shady, and if your climate is mild (as it is near the coast) or hot in summer and cold in winter (as in inland areas). If it’s shady or cool, he might suggest a fescue-bluegrass mix, like the new Eden grass. Adding bluegrass, which does not make a good lawn by itself in Southern California, lets the lawn repair itself because bluegrass creeps. Straight fescue does not and can get spotty when dogs are about.

In moderate climates (within a few miles of the coast), St. Augustine is a good choice and can stand sun or shade. It is fast, makes runners and repairs itself quickly.

If the garden is sunny and hot, Cohen would suggest tough Bermuda, zoysia or kikuyu, all creeping grasses that do best in hot climates. They go dormant in winter but can be over-seeded, even with tall fescues.

Hybrid Bermudas, like ‘Tifgreen’ and the new UC-developed ‘El Toro’ zoysia, are very tough and fast. Kikuyu grass has naturalized in many lawns and is very tough, ideal for wherever dogs may play.

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Questions should be sent to “Garden Q&A;” in care of the Real Estate section, Los Angeles Times, Times Mirror Square, Los Angeles 90053. Please include your address and telephone number. Questions cannot be answered individually.