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Olive trees have tendency to sucker at base

Q: An olive tree on the property of our homeowner association is sending up suckers from its base and along the trunk. I am thinking it’s because the tree is not getting enough water. Our landscaper continues to remove them and thinks otherwise. Who is right?

A: Suckering from the base can be a sign of a lack of water in some trees, but olive trees also sucker from the base and along the trunk easily. If you look at the base of olive trees, you will see some knots or swellings attached to the lower trunk, trunk limbs and root flares as they get older.

There can be so many of them that the tree becomes disfigured. It gives olive trees a great deal of character in their old age.

These swellings along the trunk and limbs develop from clusters of immature buds embedded in woody growth. Suckers can originate from these knots. These knots or “burls” can get quite massive in older trees.

Burls are common in other trees, particularly trees that are prone to damage from fire or animals, such as coastal redwoods. Burls are valued by many woodworkers but despised by the construction lumber people.

Suckering from the base of some trees, however, can be in response to drought. There may or may not be obvious swellings at the base of these trees. The tree finds it difficult to deliver water to its top when water is scarce.

These clusters of undeveloped buds, previously asleep, begin growing from the base. Some are scattered through the wood, and others are in clusters. Growth from the bottom is easier to support when water is scarce than growth at the top.

Some trees like ash don’t have that survival mechanism. When water is scarce, their leaves begin to scorch, push very little new growth and limbs die back, particularly during hot weather.

You could still be right. The tree may not be getting enough water, and that just makes suckering even worse. It’s best to look at the tops of the trees to make a drought determination. When water is scarce, the canopy growth suffers. When water is really restricted, there is leaf scorch and dieback by the tallest limbs.

If the tree is growing nicely and has lots of leaves, then I would say it’s getting enough water. The suckering at the base of the tree is probably normal. However, if the tree is sparse in its canopy and growth is poor and it is suckering from the base, then I would worry about enough water.

Q: When during the year should you start and stop fertilizing landscape plants, and what kind of fertilizer is best for them all? It seems to me that with acid-loving plants, cacti, palms, roses, fruit trees and annual flowers, they might all require different kinds of fertilizers and different times to apply them.

A: You could go crazy trying to follow all the different rules when fertilizing for different types of plants. Keep it simple. Let me give you a few simple rules to follow when applying fertilizers.

If plants are winter tender — in other words, they might get hurt or die when temperatures dip below freezing — stop fertilizing these plants in July. Our citrus trees fall into this category.

Lawns, bedding plants such as annual flowers and vegetables should be lightly fertilized once a month. Lawns that are expected to remain dark green during the winter should have fertilizer applied around Thanksgiving before freezing weather.

For light fertilizer applications, reduce the amount applied to half the rate recommended on the bag or container. Light applications of fertilizer can be applied every month and immediately watered in if applied early in the morning. Get in the habit of applying fertilizers early in the morning or late in the day.

The most highly prized landscape plants should be fertilized three or four times during the year: January/February, April/May and September/October. These include plants like roses, gardenias and jasmine. Again, use half rates when applying fertilizers.

Most landscape plants are fertilized only once, just before new growth begins in late January or early February. This includes all landscape trees, including palm trees.

Which fertilizer to use? You can get by with two or three fertilizers in your arsenal. That’s all.

Fertilizers have three numbers separated by hyphens somewhere on their label. They represent three different plant nutrients: nitrogen, phosphorus and potassium, in that order.

When growing plants that are primarily important because of their leaves and stems, the first number — nitrogen — should be the highest. The middle number — phosphorus — should be about one-fourth of the value of the first number. The last number — potassium — should be somewhere in between the first and second number.

When growing plants valued for their flowers or fruit, then the second number or phosphorus becomes critical. It needs to be the highest. When fertilizing these plants, the second number should be highest and the first and third numbers lower. Exact numbers are not critical, but the ratio of these three, or their proportions contained in the fertilizer, is more important.

To be healthy, plants need more nutrients than supplied by only these three numbers. But these three numbers represent nutrients needed in massive amounts by plants.

The other important nutrients are supplied by the soil. For this reason, I frequently mention the application of compost. A compost application, once a year to landscape plants, would be extremely beneficial.

Q: We have six apple and two pear trees in Ely. This year all the fruit had worms in them. The damage started when the apples were only about 1 inch in diameter. Every single fruit had worms in them. I am suspecting a moth, but I’m not sure. We sprayed with neem oil before they blossomed and after the fruit set. Any ideas?

A: This worm is the juvenile or immature form of a moth called the codling moth. It ruins the apples or pears by devouring the inside of the fruit, leaving their feces and allowing for the fruit to start rotting. In commercial apple and pear production, as many as eight cover sprays are applied to the trees every year to prevent wormy apples.

Codling moth is the most destructive insect of apples and pears in the world. We see codling moth damage to apples and pears in the Las Vegas area as well. But because we are in the Mojave Desert, this pest is not as damaging as it could be. As more homeowners plant more fruit trees, however, we will see more of this pest creating damage to these fruits in the future.

As I mentioned in passing, one method of control is using insecticides as a cover spray. A cover spray is an insecticide sprayed over the entire tree, not just the fruit. Sprays are applied often enough to create a poisonous barrier for the female codling moth. Neem oil will not work in this way against this pest.

If you choose to use an insecticide, it must be something other than neem oil, and it must be sprayed frequently over the entire tree. There are insecticides you can purchase from the store, but the secret is to apply it often beginning when the fruit first begins to develop.

Another option, pheromone traps, can either reduce the number of times the tree is sprayed or even eliminate spraying altogether. Pheromone traps are cardboard traps which contain a sex hormone released into the open air. This pheromone prevents the male codling moth from finding a female. Instead, it gets stuck in a sticky mess inside the trap.

Under some circumstances, these pheromone traps may catch enough males to prevent female moths from laying their eggs. This interruption in mating can prevent wormy apples from occurring.

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.

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