Fruiting olive trees are not permitted in Clark County

Q: I have an Arbequina olive tree in a 10-inch pot that I got about nine months ago that is about 6 feet tall. It has two trunks that are about equal in height and diameter (maybe one-half-inch thick). The two trunks join right above the soil line. Am I able to cut one of the trunks off to make it a single-trunked tree without harming it?

THE: Arbequina is a fruiting olive variety and yours is in a container. I don’t know where you live, but in Clark County a fruiting olive is not permitted by county regulation. If you live outside of Clark County, then growing fruiting olives is acceptable by regulation.

Make it a single stem instead of two. Use a sanitized hand pruner and remove the one branch you don’t like. Cut it close to the remaining stem. The tree will respond by filling in the area that was pruned over time.

You won’t notice it missing in a couple of years. The growth will be wild so it will require that you direct the upcoming growth and prevent shading. Prune it during cooler weather.

If you wait until it gets larger then it will still fill out the pruned area, but it will take longer to fill the gap you made after pruning. You can do it now and then move it to a shadier spot in the afternoon or try your luck. When temperatures cool off in the fall, plant it in full sun.

Q: I was hesitant to plant a Fuyu persimmon because some friends mentioned that they don’t do well in Las Vegas. I eventually decided to try my luck. When I planted this Fuyu back in January, it was like a 5-foot twig. Now it is up to 10 feet. I was hoping for a foot or two.

THE: The problem with growing persimmon of any kind in the desert isn’t that the tree won’t grow here. It does. I admit it is a bit touchy in our desert but not like some fruit and nut trees.

Like any fruit tree growing in the desert, it does best with amended soil and the soil covered in wood chips when you’re done planting. Nearly all our fruit trees don’t like our excessive heat.

They do best away from hot walls and surrounded by other plants with similar water needs. Like most fruit trees, persimmons are mesic in their water needs.

The problems I see with persimmon are twofold: Fruit growing in full sun is not marketable because of discoloration, and fruit production in Hachiya-related varieties is not good. There is nothing wrong with eating sun-damaged fruit but they’re not marketable (if you’re a commercial grower). Sun-damaged fruit is perfectly fine for home use.

Stay away from Hachiya-types of persimmons unless there is a pool or lawn very close to it. The same can be said about sweet cherries. Hachiya-types must be eaten fully ripe, and they are beautiful trees when surrounded by other plants or located out of the hot sun. Fully ripe fruit happens in December here.

Fuyu-types (fruit is wider than tall) are fine for home landscapes but, in my opinion, not as wonderfully tasty. Fuyu types include Fuyu, Giant Fuyu, Chocolate and Coffee Cake. Many can be eaten before they are fully ripe.

Q: I have a boxwood shrub that suddenly died. It looked thirsty so I watered it twice a day for six days. Do you know what disease or insect killed it?

THE: This answer reflects two questions I recently received about Japanese boxwoods dying. In the first, it was clearly a case of watering too often which led to root rot. In the second case, the plant also died because it was older, and the irrigation had not changed. But maybe the soil has changed.

The second question involved many more Japanese boxwood in their fifth year growing in the ground. The reader seemed to eliminate root rot as the cause of death because a dead shrub was examined for root rot. But there is another disease related to watering and caused by a similar disease organism: collar rot. Both types of diseases are common to Japanese boxwood and associated with watering or changes in soil water drainage.

I am suspicious that rock was laid on the soil surface as a mulch. Surrounding a mesic plant like Japanese boxwood with rock over a period of three to five years causes the soil to slowly lose its capacity to drain. The loss in drainage is due to a slow decrease of organics in the soil. This slow loss of organics causes the soil to get heavier, collapsing the drainage spaces and leading to poor drainage in a few years.

This loss of organics can be prevented by adding compost or other organics to a moist soil surface every other year. Mix it into the soil or spread it on the soil surface and let it rot. Simply rake the rock back from these plants, add a quarter inch of compost to the soil where there is irrigation and move the rock back. Compost rots and adds organics back to the soil in spite of the rock. Start doing this about three years after planting as a preventive measure.

Q: I have a 4-year-old Anna apple tree that was broken in a windstorm in June 2021. Since the top end of the main trunk was broken, I decided to tie it back in place and see if it would recover. It was doing fine for the past 12 months, but now it looks like the top is dying. I’m wondering if I should just cut it back this winter or wait and see what happens in the spring. And if I cut it back, should I cut just below the break or about a foot lower where two branches begin?

THE: To get the two pieces to grow back together after strong winds, you can’t wait. It must be done immediately. It depends on how fast the break dries out after breaking. Even after just minutes of drying, the tree pieces won’t grow back together after breaking. Think grafting.

Since it is an apple, combined with a young tree, any living buds beneath a break will grow. This may not happen to an older peach or nectarine. It depends on the type of tree (apple, pear, apricot or plum) and the age of the tree where it is broken.

It’s easier to cut it twice if it doesn’t work. I would prepare to prune it twice: the first time (now) just below the break and, if the tree doesn’t respond like you want, cut it a second time in late spring after you see how it responds.

At this time, prune it immediately above strong growth. After pruning now, paint the exposed stem with dilute latex white paint to protect it from the sun. Be careful of sun damage and lack of shade on the exposed stem after pruning.

Q: I have requested information from you in the past regarding my xylosma tree. You suggested I lop off the top one-third of the tree to force more lower growth and also increase the number of emitters. I did as you suggested. Now I am observing an increased number of marks on the lower trunk. Is this a problem? Is there something I could do about it?

THE: Is the plant trunk facing a hot direction? I am wondering if the trunk is getting sun exposure because it is facing south or west. Always leave lower limbs attached as long as possible to shade the trunk and increase its diameter. Many shrublike trees have a trunk that is sensitive to intense sunlight when they are young.

Another possibility could be its age and maturity. Some shrubs develop different and thicker bark as they mature.

The only way to know is by knicking the trunk with a clean knife in the damaged area. If the wood underneath the knick is discolored extensively it may be from damage due to intense sunlight. If it is not discolored beneath the knick, then it is normal and you should leave it alone.

Xylosma prefers to grow on the east and north sides of a landscape. It doesn’t like extreme heat, and it doesn’t like rock close to the trunk. Add compost or wood chips to the top of your soil and water it in. Do that about once every two years.

Moist soil and microorganisms cause it to rot. Either rake the rock back and water it in, or if the rocks are big enough, you can add it to the soil through the rocks and water it in.

If this location is hot compared to other spots, then it will struggle in the heat and sun until it gets bigger in diameter and shades itself. Adding compost/fine wood chips improves the health of the tree and, hopefully, improves its growth in that location. Rock alone is not helping its health.

Bob Morris is also 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.