Irregular amounts of water can cause lemons to split

Q: What would cause our Meyer lemons to split before they’re ripe? Too much or not enough water?

A: Usually this is irregular amounts of water. Soil that gets wet, then gets extremely dry and wet again can cause fruits of many types to split, including pomegranates, tomatoes and citrus. If we have a big downpour in Las Vegas this can also cause splitting of the fruit.

The soil gets extremely full of water, the fruits are somewhat stressed due to the summer months and the rind is no longer flexible, then the plant takes up water and causes the rind to split.

Surface mulches tend to help in cases like this because it keeps the soil from getting extremely dry on the surface.

Meyer lemon should be completely harvested no later than January. Leaving the fruit on longer than this will interfere with next year’s crop.

Q: You often discuss the need to “sterilize” garden tools to prevent the transfer of diseases. How do you “sterilize” these items?

A: What I mean by “sterilize” is exactly what is meant to a medical doctor and for some of the same reasons. Not sterilizing pruning equipment before its use is a terrible oversight. People overlook cleaning and sanitizing equipment because people don’t understand why it is needed.

Ninety-nine percent of the time unsterilized equipment is not a problem. It’s that 1 percent of the time when it becomes a problem. These are the times I receive questions about the dieback in olive, mulberry, silk tree and perhaps even ash trees.

Whenever we enter fresh plant tissue with pruning shears or saw, the equipment needs to be sharpened, cleaned and sanitized. Adjusted and sharpened pruning equipment provides a narrow point of entry, which minimizes plant damage around the cut. The concept that gardening tools should be kept clean, adjusted and sharpened is less controversial since this makes sense to people.

Equipment should be adjusted, sharpened and sterilized at the beginning of a pruning day. Equipment used for pruning should be sterilized for the same reasons we sterilize hypodermic needles and scalpels. Several important diseases are transmitted on pruning equipment. You can read more extensively about this topic this week on my blog.

Unlike a medical procedure that usually enters the body in one location, pruning involves entering the plant multiple times at different locations. So when pruning we must be concerned about transmitting a disease from plant to plant and the possibility of spreading a disease on the same plant to multiple locations.

If trees are healthy, then there is no reason to sterilize or sanitize pruning equipment between cuts or between trees. If the disease is present or you suspect a disease, sanitize between every cut to prevent the disease from spreading within the tree.

What to use for sterilizing equipment? First of all, wash the cutting surface of all pruning equipment with soap and water. Removing dirt and debris from the cutting surface improves the efficacy of sanitizing materials. It also prolongs the life of sanitizing solutions.

Sterilizing methods have been researched and there is some disagreement about what works best. Sterilizing solutions recommended include household bleach, Pine-Sol, rubbing alcohol, trisodium phosphate and household disinfectants.

This is also covered on my blog. Personally, I have used alcohol and even a cigarette lighter when nothing else was available.

By the way, bleach can be very corrosive to steel. When using bleach, oil your equipment at the end of the pruning day.

Sterilizing and sanitizing solutions have a life span. Dispose of these solutions at the end of the day and reformulate them again when needed. If there is a lot of pruning and equipment is particularly dirty, then sterilizing solutions will need to be reformulated more frequently.

Q: I am writing and enclosing photos of my pyracantha and honeysuckle problems. I cannot find information on the care of these plants.

A: Thanks for the pictures but they were not very helpful without more information. Let me tell you what I know about these plants and maybe that can help.

Both of these plants grow well in our climate in a mixed, nondesert landscape. They are not desert-adapted or desert plants so they will not perform well with rock mulch. Over time, they will perform better using wood mulch on the surface of the soil.

They should be irrigated at the same time as other nondesert plants. They should be on an irrigation valve that provides water as frequently as other nondesert trees and shrubs.

Most landscape plants require at least one fertilizer application each year in the spring or late winter. You can apply these spring fertilizers into March. Any general landscape, tree and shrub fertilizer will be good.

Pyracantha occasionally develops yellowing due to iron chlorosis so an application of EDDHA iron chelate to the soil at the same time as the fertilizer would be advised. Apply both within a foot of drip emitters on top of the soil. The iron chelate needs to be covered with mulch.

Pyracantha has a history of borer problems, particularly if it is planted in a southern or westerly exposure in rock mulch with lots of heat and intense sunlight. Borers can be active in the plants and the plant can still appear healthy for one or two seasons.

After a season or two of borer attacks, branches turn brown and begin to die back. They normally die back to where the borer damage was while the rest of the undamaged plant below this remains green. Prune these dead branches out and let the plant regrow from these areas.

Because of the dead branches, the interior wood and trunk will receive intense sunlight. This intense sunlight increases the chance of sunburn to larger limbs and the trunk. This sunburn damage attracts boring insects (borers) to those locations.

For this reason, shade from the canopy on the interior wood of the plant is extremely important. Many woody plants in the rose family, which includes pyracantha, are subject to damage from intense sunlight due to their thin outer bark.

Most of our fruit trees also are in the rose family and are subject to sun damage and borer problems.

Pruning should be pruned to maintain a moderately dense canopy. A canopy that is not so open provides filtered sunlight to the interior of the plant and reduces sun damage. You don’t want it pitch black inside the canopy but you do want filtered light, not intense sunlight, for any length of time.

Honeysuckle is a good vine to use here. However, it tends to get woody at the bottom as it gets older. This woodiness at the base can be managed by pruning it correctly.

Woodiness at the base is promoted when the vine is pruned only at the top. Several years of pruning the top results in an unattractive plant that is mostly wood without much foliage.

When pruning this plant this winter, instead focus pruning efforts on the area close to the soil surface. Find large stems originating from this area and remove one third of this older wood close to the ground. This removes a lot of plant material from the vine but promotes new growth from the pruned stems.

These types of pruning cuts encourage new growth from the base of the plant. Next winter remove one third more at the same location and you should be back on track and reversing the aging of this plant, making it more juvenile. Focus your pruning efforts closer to the ground.

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