Wait until end of September to plant trees, shrubs, fruit

People are asking when they can start planting roses, fruit trees and other landscape plants. I would hold off a bit more until things cool down. Planting can occur almost 12 months of the year in our climate, but there are times to plant that are better than other times.

For the best times, begin planting most trees, shrubs and fruit around the end of September. Planting at this time presents the fewest climate and weather problems for gardeners. This ideal time begins to taper off around the middle of November, but you can still plant.

This doesn’t hold true for plants that like hot weather such as palms and warm-season lawn grasses such as hybrid Bermuda grass and paspalum. Palms have fewer deaths when planted in the spring through the middle of summer. Avoid fall planting of palm trees.

Lawns are a different story. There are basically two types: cool-season lawns (mostly tall fescue) and warm-season lawns (such as Bermuda grass).

I like to joke that our climate grows either of them poorly; it’s not truly warm enough for the warm-season grasses in the winter and cool enough for the cool-season grasses during the summer. Combine that with our soils, and those are the biggest problems for lawns growing in our climate.

Most of the Mojave Desert sits right in the middle between warm-season and cool-season plants. That makes plant selection and growing a bit tricky.

Our climate is considered sub- or semi-tropical, which makes tropical plants like citrus, guava and moringa tempting to plant, but they may be short-lived if we get a cold winter. Don’t fall in love with these plants but, instead, consider them an experiment.

Q: My two new trees are looking healthy and well-established. I sense it’s time to do some limb removal. Both tops are forked. I’m wondering if removing a branch will help establish a single leader and promote more vertical growth and correct a lopsided droop.

A: Corrective pruning should be done at planting time, usually during the spring or fall months, but done during the first couple of years. Look at the “crotch” where these forked limbs come together. If this crotch has a V-shape, then it needs to be pruned this winter. As the tree grows, the crotch will weaken, and the weaker of the two branches will split away from the other.

If this crotch has a U-shape, then let it go. The point of attachment for both branches is strong enough and does not present a future hazard. Now when the plants are young is the best time to make these structural decisions.

Wait until leaf drop for corrective pruning if the tree is deciduous. In Las Vegas, that could be anytime from mid-November to mid-December. Major structural changes to the tree should be done during the winter months.

If the tree is evergreen, like a pine or olive tree for instance, then wait until it’s cold enough that regrowth after the pruning cut is made will not occur. That will usually be around mid-October to Nov. 1 at the earliest.

Will it kill these trees if you do it other times of the year? No, but it’s not the ideal time to do it.

Don’t remove too much from the tree when it’s young, but now is the time for corrective pruning. Corrective pruning addresses future problems and helps it look better.

The time to encourage balanced new growth in the tree is when it’s young. This helps shape the tree more rapidly during its life. The tree will rectify everything wrong with it over time, but pruning now corrects misshapen growth faster and makes it look better.

Q: We had three mock orange bushes that lined the walkway to our front door for several years. Last year the middle one died. The leaves looked as though they are — for lack of a better phrase — getting sunburned, and then it progresses to the point where the plant dies.

Thinking it was just old age, we cut it off down to the stump. Now another one that gets even more direct sunlight is almost gone, and the third is showing some of the same symptoms.

A: You are right. It is sunburn but it’s sunburn because of improper pruning. These plants are suffering from landscaperitis: an overzealous pruner got hold of the mock orange bushes and cut them back too far, probably just in time for the intense heat and in a location with very intense sunlight.

If they were pruned in the fall when it is cooler, watered and fertilized after pruning and given enough time for growth before it got hot again, then they would probably be OK. But when plants are heavily pruned in late spring, exposing major limbs to direct intense desert sunlight, then the hot summer and intense sunlight can kill these limbs. Plant disease was not the primary cause of death.

What to do? All landscape plants have a life expectancy. When they are mismanaged, then plant life expectancy is shorter. Replace these plants with something appropriate for that spot.

Determine the size needed and the exposure they will receive in direct sunlight. Avoid pruning plants just before it gets hot or when it is already hot.

When “blow and go” landscapers do the landscape maintenance, expect to replace plants about every 10 years as they progressively get worse to look at. It is the cost of doing business with them.

Q: We moved here from Denver and are trying to get our vegetable garden adjusted to our new environment. Las Vegas is very different from what we are used to.

A: Vegetable and herb planting and harvesting requires that you shift your warm and cool seasons and adapt to this warmer, desert climate. Denver weather is definitely seasonal; it has a distinct cool and warm season for vegetables. The Las Vegas climate is less seasonal with planting seasons harder to discern.

Las Vegas has basically two seasons: two cool seasons and a hot season. There is a fall cool season that is usually ignored when planting vegetables in colder climates. Our warm season during the middle of summer may not the best for tomatoes, peppers and eggplant, but it certainly is a productive time for melon and winter squash.

Both locations are windy, so vegetable and herb gardens benefit from wind protection. While many warm-season vegetables stop producing because of the heat in Las Vegas, they continue to produce in Denver where it’s cooler in the summertime. Tomatoes ripen in June but produce sporadically after that because of the summer heat of Las Vegas. But fall tomatoes will do well in Las Vegas as well as cool-season vegetables.

Both cities are renowned for their sunlight intensity, but the summer heat and low humidity of Las Vegas can create vegetable havoc during the summer. Vegetables in both locations will benefit from shade cloth.

Q: Can I grow lantana without drip irrigation?

A: I assume you’re asking if it can be hand-watered. Yes, it can, but is the time and effort worth it to you? Whenever hand-watering with a hose, construct a basin or doughnut around the plant to hold the applied water. The water must be held in place around the plant long enough so that it soaks into the ground and wets the roots.

The depth of the basin and its diameter depends on the size of the plant. In the case of lantana, the basins can be about a foot in diameter and only a couple of inches deep. When hand-watering, fill the basin to its tippy-top with water so that it stays in one place long enough to wet the 12-inch-deep roots of lantana.

In the case of trees, the basin must be much larger and deeper. The basin is constructed large enough to wet the roots beneath the trees canopy.

For large trees (pines), the soil should be wetted to a depth of 36 inches, medium-sized trees (such as olive and fruit trees) to 24 inches and smaller trees and large shrubs (desert willow) to 18 inches deep.

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