Give large plants space to grow

I will be holding a workshop on pruning stone fruit trees (peaches, nectarines, apricots, plums) from noon to about 3 p.m. on Dec. 17 at the Master Gardener's Orchard. We also will be talking about pruning grapes -- both table and wine grapes -- at this workshop. Bring your bypass pruning shears if you want to get some hands-on experience. For directions to the orchard, call the Master Gardener help line at 257-5555. If you miss that workshop, other classes will be offered on pruning during January.

Question: We see a lot of small to very tall junipers, as well as various bushes planted up close against the exterior of houses and buildings. As we consider planting trees and bushes for shade, which plants and/or trees do you recommend in which the roots will not pose a risk to the structure and/or foundation?

Answer: I wouldn't worry too much about getting shrubs close to the house. The problem arises when we plant things that will grow to be very large close to a house or driveway.

Generally speaking, if you keep shrubs a distance away from the house at least half of their mature height, you will have no problems. For example, if you plant a Texas ranger shrub that has a mature height of 6 feet, it should be no closer than 3 feet from the foundation. Trees that have a mature height of 20 feet should be no closer than 10 feet from the foundation.

There is another problem that is perhaps more important to consider, and that is the closest you should put water. Because of our soils here, I would never put a water source such as a drip emitter closer than 3 feet from the foundation or a patio, sidewalk or driveway. There are just too many locations in our valley with high sulfates, and the corrosion problem and weakening of footings for walls is just too great to risk it.

Trees with notorious roots are mulberries, poplars (cottonwoods), willows (except desert willow which is not really a willow) and those plants common to bottomlands.

Q: I have a crepe myrtle, raywood ash and mulberry tree, all about 3 to 4 years old. I want to make flower beds around the bases, and my girlfriend told me that the flowers would have bugs that would infest the trees, such as borers, and eventually kill them. Is this true, or can I plant certain types of tall grasses or specific flowers that would not affect the trees?

A: I would not worry about bugs in the flower beds infesting the trees. I would, however, be more concerned with the fact that the flowers will have to be watered much more often than the trees and you could end up with some disease problems in the lower trunks due to keeping the soil so wet in that area for the flowers.

If you are going to do that, make sure that the soil drains away from the tree trunks and does not keep the soil wet for extended periods. I would keep flowers away from the trunk at least 2 feet and mulch the area around the tree with 2 to 3 inches of wood mulch. Otherwise, use some herbaceous perennials or lower-water-use annuals that don't require water as often.

Q: I have been losing a lot of trees to the borers in the last one to two years, which includes flowering plum, mimosa, screwbean mesquite, an apple, cherry and peach. How can I save these types of trees from borers, as well as my chaste tree, Meyers lemon and a pine? I fertilize the fruit trees one to three times a year with fruit and nut tree fertilizer. All others get fertilizer several times during spring and summer months.

A: I would not worry about the chaste tree or the pine concerning borers. I would protect fruit trees by painting the trunk and lower limbs with white latex paint diluted 50/50 with water to help reduce borer problems.

Whenever you have fruit trees, and other trees susceptible to borers, leave as many lower limbs on the trees as possible to protect the trunk from direct sunlight. Be careful when you prune and don't open up the canopy too much by removing so much wood and allowing light to sunburn the limbs.

Mimosa's biggest problem is a wilt disease that causes the top to die back, which can lead one to assume it is borers. There is nothing you can do about this disease and it can spread to other mimosas through root grafts. You are lucky to have one that old.

The lemon is not that susceptible to borers either, but I would still paint it. There really is not much you can do about spraying for borers with a pesticide because we do not know the correct timing for spraying to kill them before they enter the trees. Paint and appropriate pruning are your best solutions.

Q: I am a personal chef and am relocating to Las Vegas from New York. How do herbs like the Las Vegas climate? I am interested in dill, mint, basil, thyme, oregano, parsley, rosemary and sage. Also, we have beautiful, established geraniums here in New York. We also have a great clematis and rosebushes. Do we move them to Las Vegas or give them to our friends? Thank you for your sage advise (pun intended).

A: Most herbs will work well here with a little bit of care and some light shade cloth on the more tender ones. The best times of year are in the spring and fall months for quite a few herbs. Some struggle during the summer due to high light intensity and low humidity.

Geraniums will be a challenge, and you will have to give them some protection from sun and wind. They like the spring and fall months best, as well. Be prepared to modify the soil heavily here to get good results. The soils are desert soils and not friendly to nondesert plants, so we have to do a lot of manipulation to it from the start.

Roses do very well here but struggle, like many of the plants you mentioned, in the summer. In many ways, our summers are our winters.

I have seen clematis here, but they will struggle unless protected from late afternoon sun and wind. I would not leave any of your plants behind, but be prepared to be frustrated for a while until you get the hang of desert gardening.

You will be surprised at what can be grown here with a little bit of knowledge and effort.

You will find that other things will grow very well here and you may add some new things to your menus such as napolitos.

Q: I have seen and heard different things about when to prune trees.

I have both evergreen and nonevergreen. I see some neighbors cut their trees way back with stubs for branches and very little foliage and others who trim.

Should I be cutting my trees way back prior to winter or when is the best time to prune?

A: Heavy pruning is always done in winter or, in the case of plants that are "bleeders" (sap oozing after you prune them), early spring just at bud break.

That is one reason why elms should be delayed in their pruning, for instance.

They are bleeders, and that is why we usually delay pruning grapes, as well.

When regular maintenance pruning is done, and if it is done correctly, no one really would notice that the tree has been pruned.

If done correctly, maintenance pruning would need to be done once every three or four years. This is why good tree trimmers don't get noticed.

I have seen some beautiful work done in Las Vegas by some local professionals. But who would notice it unless you are looking closely?

The ones we notice are the tree butchers.

When done incorrectly, the tree will obviously look like it has undergone radical surgery.

This type of tree pruning is called tree butchery and is never acceptable. I could write a whole column on the subject, and it is a personal sore point with me.

Some professionals say they are "forced" into plant butchery by their customers because customers sometimes are ignorant of the right way to prune and don't want to be bothered again with pruning for years if possible.

But in fact, trees that are radically pruned or butchered will need much more upkeep so that they look good and are not a safety liability to the public.

I believe tree butchers should carry malpractice insurance.

Bob Morris is a horticulture specialist with the University of Nevada Cooperative Extension.