Proper pruning, irrigation act like steroids for trees

The University of Nevada Cooperative Extension Master Gardener Program offers gardening classes to the public as well as comprehensive horticultural instruction to those wishing to become master gardeners. All classes are held at the extension's Lifelong Learning Center, 8050 S. Maryland Parkway. For more information, call 257-5555.

Q: This fall, I planted a few 24-inch box African sumacs and California multitrunked pepper trees. How can I maximize their growth during the next few years? With so much talk in the papers recently about steroids, is there something comparable for trees? When is the best time to thin out extra branches and how aggressive should I be?

A: There are no plant steroids, so to speak, that will help you create the plant world's equivalent of Mark McGwire. Perhaps in the future there might be, but there is nothing now. Most likely if it is done to the plant world, it would be through genetic engineering.

My best advice to you would be to do one initial pruning at the time of planting to help create the major limbs coming from the trunk. Each month during the growing season, remove new branches that will be unnecessary. These would be branches that are crossing, damaged, weak and growing back toward the center of the tree.

Fertilize the trees every two months from January through August. Water them deeply at each irrigation but allow the soil to dry between irrigations. Avoid frequent shallow irrigations as this may cause the trees to weaken and blow over in strong winds.

You want to push new growth as quickly as possible and in directions that create size. Growth that does not increase size should be eliminated. Later on, the trees will create volume in the canopy.

Q: I want to grow a vegetable garden this coming summer. I live in Sun City Anthem and my backyard has desert landscaping. I have been informed that I have to replace the top 18 inches to 36 inches of natural soil with store-bought top soil. My question is how much of the natural soil needs to be replaced with top soil? And what brand or kind of soil replacement is best for a general garden?

A: I don't agree that all of your soil needs to be replaced unless the soil is extremely rocky and you plan on growing root crops like carrots and beets. All you would need is about 12 inches of new soil if you have good drainage beneath it.

Preparing existing soil for vegetable production is going to be very labor intensive. If you are unable to provide this labor, then importing soil for vegetable gardens and creating a raised bed might be a better alternative.

There are numerous books about vegetable gardening. A couple that you might want to consider would be "Square Foot Gardening: A New Way to Garden in Less Space With Less Work" by Mel Bartholomew and George Brookbank's books that are focused for our climate area. Bartholomew's book will give you some ideas about how to garden in very small spaces and Brookbank's book will give you some details about planting dates, working with our soils and irrigation.

By the way, you do not need to build expensive walls surrounding a raised bed. If the bed is large enough, its sloping sides are sufficient to contain it.

Unless there are some unusual circumstances where the soil is toxic, most vegetables that are harvested above ground should grow well in amended native soil. Look around you. Are plants of all different kinds growing in your neighbors' yards successfully? If they are, chances are good that your soil will be fine.

We do have soils in our area that are toxic due to high amounts of naturally occurring boron and sodium, but you would see these problems popping up with other plants as well. The most critical issues for you to address will be drainage of your soil after it is irrigated and the lack of organic material.

If you choose to tackle the job of preparing your existing soil, I would rake away the rock mulch from the vegetable site. Make sure your garden area has a minimum of six hours of full sun each day. The best sun in the summer is in the morning and early afternoon. It is best if the garden spot has shade on it from 3 p.m. to sunset.

If the soil beneath the rock mulch can be dug, dig as deeply as you can to loosen the soil. If it is difficult to dig, try flooding the area slowly with a hose to a depth of at least 12 inches. Allow the soil to dry and drain for one week prior to digging. Remove rocks larger than a golf ball.

You can dig by hand or rent a very heavy-duty rototiller. A rear tine tiller would be best. If the soil can be dug by hand when it is moist, a rototiller will probably work fine. Work the soil as deeply as possible with the rototiller; the key to using a rototiller is to have moist soil. Rototilling dry, compacted desert soil that has never been loosened or has been compacted with equipment during construction will shake you and the tiller to death.

There may be quite a few soils where a rototiller will not work even when they are moist. In cases such as these, you may need to loosen the soil first with a soil trencher such as the kind used for burying irrigation pipe. Cut trenches at least 12 inches deep.

Once the soil has been opened either by rototilling or trenching, apply 4 inches to 6 inches of good quality compost. Get some high-phosphorus fertilizer such as treble superphosphate and apply it evenly over the entire garden spot. If you are an organic gardener, use bone meal or rock phosphate. Rototill all of this entire area as deeply as possible.

At this point, you have a garden area that has native soil, compost and starter fertilizer mixed together but not chemically working together. Think of it as making a cake and adding the dry ingredients. The dry ingredients do not work together until the mix becomes wet. They work together faster when the mix gets warm.

It is best if this garden mix has some moisture and heat before planting. This will require you to water the entire spot several times. If it is cold outside, then cover the area with clear plastic and let it cook or warm up for a time. This will allow the garden mix to stabilize.

Be sure to bury the edges of the plastic under soil, pin it down along the edges and put some weights in the center. You might also put stakes along the edges and run rope or cord crisscrossed back and forth over the top of the plastic. If wind gets under the plastic, it will keep blowing it off of the garden spot.

Check with your nurseries and garden suppliers for compost and garden soils. There are some good ones out there.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at extremehort@aol.com.