Plants in protected microclimate better suited to weather cold

Q: Are there any do’s and don’ts you can give regarding covering plants to protect them from the winter weather here in Las Vegas? I have some small citrus that are in the ground.

A: Probably the single best publication on this topic comes out of Arizona. You can retrieve that off of my blog, Xtremehorticulture of the Desert, or Google “protecting plants from freeze damage.”

I have not thought much about using Christmas tree lights around trees or shrubs unless you can capture that heat. And those little LED lights don’t put out much. In my opinion, the most sustainable way is to find landscape microclimates and cover plants with a blanket of some sort.

Stay away from open areas that get windy and narrow passageways between homes. These narrow spots tend to increase wind speed. The two damaging factors are low temperature and wind. Focus on these two factors to protect your plants.

Streets that run north and south in the valley tend to get colder than streets running east and west. I like to call these our urban canyons. The lowest parts of the valley tend to collect cold air.

Q: What do think the problem would be with my three gopher plants? They seem to be getting enough water.

A: This plant is a Mediterranean plant, which means it likes soils that drains easily, hot summers with infrequent irrigations and cool rainy winters. Whenever I see branch dieback on plants like this it usually indicates there is too much water remaining in the soil between irrigations.

This means it is either watered too often or the soil does not drain very well or both. If this is the case, you will not solve this problem by simply giving it less water. You either have to take up the plant, amend that soil and replant it or move it to a new location that has improved soils and can handle frequent waterings.

If you cannot change how often the water comes on, you will have to change how rapidly the soil can drain the water. You will not change the soil by adding sand. This will make it worse. You have to use amendments such as compost and perlite.

Once you have solved this problem you could cut this plant back to 3 or 4 inches in height and have it regrow again. Dead portions of the plant you can remove completely. Fertilize lightly in the early spring.

Q: Can you tell me what is causing the leaf scorching on my black mission fig tree? Is this normal for the fall?

A: The leaf scorching that you’re seeing is soil related. This usually means either the plant is not getting enough water or there are salt problems.

Because you are producing nice juicy figs I am guessing it’s a salt problem. I would do two things to your fig tree.

First, I would move the drip emitters further from the trunk, usually about 18 inches. As this tree gets larger it will need more emitters. This tree should have four emitters 18 inches from the trunk and spaced like a square with the trunk in the center of the square.

Secondly, I would cover the area under the tree with more wood mulch to a depth of about 4 inches and covering an area at least 6 feet in diameter with the trunk being at the center of that diameter or circle.

The fact that you are getting nice juicy figs tells me the plant is getting enough water. What I sense is that the roots are now growing beyond the planted area and are encountering salty soils.

I would flood the area with water to push the salts away from the roots. You don’t want to push the salts back toward the tree but you want to push them away from the tree or you want to push them deeper into the soil below the roots. This requires enough water to wet the soil down to a depth of about 18 inches.

Take one of those small stationary sprinklers that attach to a hose and turn up the water pressure so that it sprays water on top of the soil in an area about 6 feet in diameter and flood that soil to leach the salts.

You want an even application to the surface of the soil with little to no puddling, entering the soil and pushing the salts in the wave to a depth below the roots, which is typically about 18 inches deep. Don’t forget to fertilize your fig tree in January.

Q: Two of my Italian cypress trees died so I am replacing them. What size do you suggest I buy and how to I prepare the area before planting and what is the correct way to plant them?

A: Get the smallest plants you can find if that size is acceptable to you. I, personally, would start with 5-gallon plants. They will catch up to larger plants in a very short time.

Amend the soil with about 50 percent compost to a depth equal to the depth of the container. The hole should be dug a distance three to five times the diameter of the planting container.

It is more important to dig the hole wide than it is deep. If the soil is particularly hard to dig beneath the container then I would take a posthole digger and dig a chimney at the bottom of the container and fill that hole with amended soil to improve drainage.

Thoroughly soak this area several times after you plant the trees. Five-gallon plants should not need to be staked. With improved drainage they should be able to handle more frequent irrigations without problems if that is necessary.

Fertilize them once in January or February with an all-purpose tree and shrub fertilizer.

Put them on a valve with other trees and shrubs. They will do fine on the same valve with most of your landscape trees and large shrubs as well as fruit trees.

Q: We are ripping out an old, dead lemon tree and would love to plant my potted dwarf citrus trees in its place about a foot from the garage. They would be getting slightly less sunlight, but sun for most of the day. They have all been in pots for about four to five months. Do you anticipate any problems with this idea?

A: Four to five months in a pot is not a problem. The roots are still exploring the soil in the container and have not been in long enough to cause a problem. They should be fine in a warm location protected from the wind and protected from winter cold.

Put your drip emitters a foot to 18 inches from the trunk away from the garage to encourage root growth away from the foundation. This will keep the soil close to the garage drier and less likely to cause salt damage.

It would be better and more attractive if the plants were trained against a trellis or espaliered. You will need to keep the branches pruned off that are growing toward the garage.

Some people will have a problem with it being planted that close to the garage. It is not going to be a problem for the garage. The roots will not be a problem for the foundation. We see citrus espaliered near a wall or foundation a lot.

Q: This season our lantana has done poorly. For each plant we dig up there appears a bunch of grubs. What’s going on?

A: Several people have contacted us concerning grubs feeding on the roots of lantana. There are several types of grubs, usually the juvenile forms of certain types of large beetles, that feed on tender plant roots of all different types.

They are relatively easy to control with traditional and organic pesticides. Many of the pesticides using plant-based oils like rosemary, wintergreen, clove and thyme have been effective on these insects.

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.