Harsh desert sun can damage apples

: I kept an article you wrote about apple trees from June 2007. From what I have read, they need to have full sun. I have space on the east side of the house which gets shade. Will they do OK there? It is between the house and the street and I was thinking that some shade in summer will keep the fruit from getting baked in the sun.

A: You need about six to eight hours of sun a day to get a decent crop of apples. If you think you can get that much light, you could pull it off. Anything less than that, unless you have a lot of bright indirect light, will just lower your production level and the quality of the fruit produced.

You might try trellising the fruit trees near a wall that gets lots of light in that location. But you are right, a decrease in direct light, particularly late afternoon light, will reduce damage to the fruit. Thinning apples more heavily on the south and west sides also will reduce the amount of sun-damaged fruit.

Q: What special care should I have with bougainvilleas in the Las Vegas winter? I am a new resident. Should they be covered to avoid freezing in colder months?

A: For winter protection on bougainvillea it just depends on where you live. If you are in a warm part of the valley or in a warm microclimate, it may never freeze and you will have few problems with winter damage. If you are in a cold part of the valley, such as low spots near the Las Vegas Wash or in the northwest where we get cold winds, then it may freeze to the ground.

It also depends on the year. Some years nothing in the valley freezes while other years it can get very cold.

In most cases, if it does freeze to the ground, it will grow back from the roots if the plant is well-established going into the winter. If it is weak and poorly established, it may not survive.

It will help if you can put down a thick layer of mulch over the roots before it gets cold. I would suggest about 6 inches. It will help insulate the roots and prevent them from freezing, which they will not survive.

You can throw a blanket over the plant during the coldest nights to help protect it from the cold. Take the blanket off in the morning after the night or early morning freeze period has passed. Next spring, as new growth appears, trim off freeze-dead stems from the plant.

Q: I planted three regular-sized oleanders last spring: white, red and pink. Only the pink one has flowers now and is the only one that continuously had flowers since planting. Shouldn't all of them have flowers at the same time? Aren't oleanders supposed to have flowers year-round?

A: The pink or salmon-colored one may be a dwarf variety. There are also differences in varieties. The standard-sized oleanders may have to be much older for flowering to begin.

Flowering will not begin until the oleander has reached an age when growth slows and flowering/reproduction begins. If the pink is not a dwarf form, it just may be ready to flower while the others are not. Just give them some time.

In the meantime, give them plenty of water and not too much nitrogen fertilizer; focus on high-phosphorus fertilizers to help promote flowering.

Q: I'm planning to buy a lemon tree for my backyard. What type of soil do I need to use when I plant the lemon tree? What type of lemon tree can I plant in the Las Vegas Valley where I live? And for the winter time what should I do with my lemon? For all citrus trees, does the soil need to be the same? What type of spray should I use to keep them bug-free?

A: The most commonly planted lemon in the valley is Meyer lemon. It can handle wintertime temperatures down to about 22 F. At temperatures below this you may lose it or have light to severe damage.

Find a warm microclimate in your yard to help protect your lemon. Otherwise, plant it in a large container and move it into your garage until all threats from freezing have passed.

Plant lemons either in the ground or in containers. When planting in the ground, use the same soil you took from the hole, but amend it with at least 50 percent compost at the time of planting. Also mix a starter fertilizer into the soil. Stake the tree to make sure the roots do not move during the first few months. Water deeply and thoroughly at each irrigation.

Mulch around the trees on the surface of the soil with 3 to 4 inches of wood mulch to a distance at least 3 feet from the trunk. Lemon trees are relatively pest-free so you should require few pesticides.

Q: I have a loquat tree located in a courtyard. It seems to suffer from either a nutrient deficiency or lack of water. The mature leaves turn brown all along the edges and this progresses inward. It seems to be getting progressively worse. New leaves are not a dark green like one would expect on loquats and seem small and stunted and about three shades lighter.

A: Loquat is a semitropical fruit tree that is thought to originate in subtropical cooler parts of China. It has been grown in Japan for more than 1,000 years.

It is out of its climate zone when it is grown in the desert, so it needs some help with soil amendments at planting time and organic mulch. The leaves will scorch in the desert heat, low humidity and dry winds. It is best grown in protected areas in the yard away from wind and late afternoon sun. It does not like to go without water so water stressing it will cause problems, in particular borer problems.

A big problem on loquat is borers. Check the limbs of your tree for borer damage. Symptoms of borers are similar to your description. This would be flaking off of bark with sawdust under the flaking bark where the borer or borers were feeding.

Although it likes a similar climate to citrus and is a bit more cold hardy than most citrus, it does not like the hot part of the yard like citrus can endure. It also will help if the trunk and limbs are whitewashed to help reduce the heat load on exposed wood. It also will do better with a full canopy of dense leaves so fertilizer applications are important.

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 morrisr@unce.unr.edu.