70°F
weather icon Clear

Water – too much or too little – root of problems

Q: I planted six Podocarpus in March, three by the north wall and three by the south wall. Now the three on the north wall have leaves that are turning brown. The three on the south wall are fine. I didn’t realize that the trees would get this much sunscald. Any suggestions on what I can do, besides give them macronutrients and hope for the sun to change course?

A: Judging from the picture you sent, I really do not think it’s going to be a continuing problem for you on the north wall once this is corrected. The south wall will be more of a challenge. I do not think this is sunscald; it is either a lack of water, watering too often or a lack of soil improvement at the time of planting.

Since the problem you are having seems to be on the north side, I might guess that you are keeping the soil too wet or they are not getting water.

The north and south sides are radically different microenvironments. It is much hotter on the south side than the north side. This means plants on the north side should be watered less often than plants on the south side.

Notice that I said less often. The plants on both sides should receive the same amount of water, but the difference should be in how often they are watered. To accommodate this difference, plants on the north side should be on a different valve.

It looks like you have rock for surface mulch. That will be a mistake for these plants in the future. They will be OK for a year or two, but you should consider changing this to wood mulch instead of rock.

If you are going to have problems with this plant, it will be on the south side. These plants will tolerate a little bit of drought and infrequent watering, so treat them like landscape trees and shrubs with deep but infrequent waterings.

In other words, do not water them daily. At these temperatures, as long as you have good drainage, twice a week with about 10 gallons for each plant should be adequate on the south side if they are on drip emitters.

On the north side, once a week would be adequate. If they are on drip emitters, they should have an emitter on each side of the plant. Put the emitters toward the front of the plant.

After mid-October you can cut your watering to about once a week but give the plants the same amount of water. In mid-December you can water the plants about every 10 days.

These are evergreen plants, so damage to the leaves will not disappear until new growth covers it.

Q: We had three healthy palms in our yard for many years. Just recently, we had to have one removed, but were not able to determine why it died. Today I found this frond on the ground, and it looks like a fungus on the back of it. Can our palms be saved with treatment?

A: From my perspective, there are two options. The first is to recognize that white fuzz on leaf fronds of many of palms is normal.

Looking at the photo you sent, my first reaction was that it was normal.

The second option is that it is a disease or insect problem that I have not seen before. We do have mealybugs and scale insects that cause a similar white fuzzy appearance. This normally occurs on palms growing indoors, not outdoors.

I still tend to think that this is a palm with normal white fuzzies on the leaves. What is troubling is that you told me one of your palms died. If the palm is well-suited to our desert climate, death would be rare.

I went searching for diseases that might give the same appearance. I could not find any.

Many people assume that palm trees are low in water use. They are not. Palms survive nicely in the desert near an oasis where they can drink freely. They don’t survive in the middle of a desert landscape with a minimum amount of water.

A telltale sign that they are not getting enough water is poor development of the fronds; they may be smaller than normal and scorched around the margins of the leaves. Eventually the bud in the center of the palm dies, thus killing the entire palm.

Palms can be weakened if they are not receiving enough water, if they go through a hard winter that stresses the central bud, if they are severely pruned in late fall to look like a feather duster or if new palms are planted in the fall instead of spring and summer.

My gut tells me that your palm frond with the white fuzzies is one of the normal palms and that your palm that died was killed by bud rot.

Q: I saw an avocado potted tree at Lowe’s hardware and was thinking of planting one in my backyard. My question is: When is the best time to plant this tree? Is fall OK? I’m thinking of the winter freeze that might occur. I hope to hear from you soon, in case they sell them out.

A: Remember that avocados are very iffy here in the Las Vegas Valley. It will freeze back, so keep it against a hot south or west wall, trellis it near a warm winter wall and keep it draped with some sort of sheet or crop cover at nights when you think it might freeze.

Pick a variety that is more cold-hardy, if you can find one. Any way you cut it, it will be an experiment; so get ready for the possibility of losing it.

You can plant it this fall, but protect it this winter and in succeeding winters.

Wow. I don’t think I ever had so much email regarding a question as I did about my comments concerning rabbits on the west side of the valley (View, Sept. 13). Evidently my joke about planting more carrots was not appreciated by some. Others took it as humorous.

It is nice to know people are reading my column. Stay tuned. Next week my column will talk extensively about rabbit control.

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.

Don't miss the big stories. Like us on Facebook.
THE LATEST
Olive tree will outgrow container so plant in ground

Desert willow can look shaggy during the winter because of the brown seedpods that hang from the tree. The seedpods provide a good supply of birdseed for various desert birds during the fall and winter months.

Verticillium wilt cause death of single branch

Verticillium wilt disease plugs the internal tubes that carry water from a tree’s roots to the leaves. It commonly infects a single branch, causing it to die and appear like it is not getting enough water.

Citrus plants have different tolerances to winter cold

There are two strikes against citrus growing well in the Mojave Desert. The first is their variable tolerance to freezing temperatures during the winter. The second strike is that oftentimes citrus trees flower in early spring when very light freezing temperatures are possible. Tolerance to these freezing temperatures is practically nil.

Control whiteflies as soon as you see them

Whiteflies are a bad insect problem for any plant. Their populations grow so quickly that small numbers lead to large numbers very fast. For that reason, it’s important to get them under control early, as soon as you see them.

Cutting tree roots always damages the tree

You can typically remove about one-third of the total tree roots with no problem. This is done sometimes when trenches are cut in the soil for burying irrigation lines. But when roots are cut, about one-third of the top should be removed as well.