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Some plants affected by cool temperatures

This cool weather has caused some unusual plant problems we normally do not see in the hot desert. One reader contacted me to let me know that his tomatoes were not quite the size of a tennis ball, still green and didn’t seem to be growing anymore.

Another reader told me his newly planted grapes were not growing. Both readers wanted to know what to do.

The answer to both is to wait. Both of these plants love warm weather. In fact, grapes love the heat.

Our nighttime temperatures have been in the 50s and 60s. Most plant growth occurs at night, not during the day. Tomatoes get chilling injuries at 45 F.

Be patient. It will get hot. Tomatoes will ripen. Grapes will grow an inch every one to two days when temperatures are above 100 F. All we need are warm night temperatures.

Q: My newly planted grapes aren’t really growing fast and are a bit more yellow than dark green. I am wondering if I need to water more; I am only watering two times a week. Or do I need to water less? Or should I add something to the soil? Or do nothing and stop worrying?

A: Grapes love the heat. It is probably just not warm enough. Watering twice a week is right when temperatures are beginning to warm.

Apply about 5 gallons each time you water newly planted grapes. Put a steel stake next to them or a piece of rebar and tie them tightly to it so they are straight. Use the stretchable green nursery tape. Do not use wires.

If you are planning to trellis these grapes, remove all leaves along the trunk except the new growth at the tip. You do not want side shoots to develop along the trunk unless you are growing it in a tree form.

The leaf yellowing could be caused by cool nighttime temperatures or a lack of nitrogen fertilizer. Apply nitrogen fertilizer once a month to the soil around the trees and water it in. Do not apply closer than about 12 inches to the plant or you could burn them or worse.

I see from the pictures you sent you have a lot of rock mulch surrounding your fruit trees and vegetables. Our soils have horribly low amounts of organic content, some of the lowest on the planet.

Grapes, all fruit trees and vegetables, including strawberries, do not like rock mulch at all. This will be a problem in the future. They like “organic” soils, not rock or mineral soils. The small amount of wood chips you have spread a few inches around your plants will not help them at all.

Wood surface mulches need to be at least 3-4 inches deep and a distance of at least 3 feet from their trunks. Keep wood mulches several inches away from the trunks of young trees and vines.

Q: I live in Sandy Valley and will be building some raised bed planters in my backyard. I have seen gopher mounds all over the property and am wondering what is the best way to get rid of them before I start this project. One neighbor says they are so prevalent on the north end of the valley they ignore them altogether.

A: Gophers are tough to control. The options are to kill them, exclude them from desirable plants or catch and relocate them. When gophers have other food sources in the neighborhood, using repellent plants in your garden might work since your neighbor’s plants will then seem more delectable.

When gophers find a food source, they make more gophers. Your raised beds will encourage them to set up a base camp, living quarters and a dining commons. The bottom line is they are attracted to your water and the soft, juicy succulent plants you are growing.

There are baits and poisons you can use but you’ll have to be very careful not to poison other animals in the process. Your best option is probably to exclude them from your growing area with a wire mesh barrier. You would need to move all your susceptible production into raised beds and place wire mesh at the bottom of the bed before filling it with garden soil.

It is best to read through this for your options: http://cesonoma.ucanr.edu/files/27165.pdf.

Q: I just bought a new house with a big yard in Summerlin. I am Asian and there are three trees I want to plant most but I don’t have any experience: jujube, Hachiya persimmon and white saucer peach. I read some of your articles and decided to ask your advice before I take action.

A: Jujube, or Chinese date, grows extremely well in our climate and you will have a lot of success growing it here.

The biggest problem is its invasiveness. Jujube suckers from its roots grow in new locations wherever there is water. These can be distances of 5 to 20 feet away from the mother plant. Over time, you could have a forest of jujube from a single plant. Just keep the suckers eliminated when you see them.

Sadly, Hachiya persimmon does not perform as well here as Fuyu and other persimmons. We have trouble getting good fruit retention (fruit staying on the tree) after the fruit has set. Plenty of blossoms but the fruit drops when it gets about ½ inch in diameter and the tree produces only a few fruit. I would suggest trying different varieties of persimmons, such as Fuyu, Giant Fuyu and Coffeecake).

The white, flat peaches perform very well here with a very high sugar content and excellent flavor. I would suggest donut peaches such as “Stark Saturn” or “Sweet Bagel” varieties. These peaches may also be called saucer or peento peach.

If you keep your trees healthy by planting with plenty of compost mixed in the soil and covering the soil surface with wood mulch, you will have fewer problems. You can always email me with specific questions.

Q: Our flowering plums have been infected by what was diagnosed as “sooty canker” disease.

They were treated by arborists but the blight continues. Infected limbs were cut until one of the trees needed to be removed entirely. I am advised this blight has become epidemic in the Las Vegas Valley. Is there a solution to cure or at least use as a treatment for sooty canker?

A: Be careful on any diagnosis of sooty canker. There are a lot of natural things that can look like it and if you’ve never seen it before or don’t have much experience around it, it can be easily misdiagnosed.

Sooty canker disease causes limb dieback and the bark of the dead limb to peel away revealing a black, sooty powder on the wood. When you take your finger and rub against this black powder it will come off on your finger and look just like soot from inside your chimney.

There are other natural black “powders” on limbs that also will rub off on your finger. But sooty canker is jet black on your finger and unmistakable once you see it. I will post a picture of sooty canker on my blog so you can see what I’m talking about.

I disagree that it is an epidemic in Las Vegas. It has attacked a small number of trees every year at about the same rate for the past 30 years. Many trees can become infected but we see it most frequently on mulberry and poplar (cottonwood) and occasionally on ash and elm.

I don’t remember seeing it on truly desert trees such as mesquite, acacia or palo verde.

It can be spread easily on pruning equipment if the equipment is not disinfected between cuts and between trees. Be very careful when this is diagnosed. If a limb is dead, it is dead and must be removed. We don’t want to be removing limbs with the wrong diagnosis.

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.

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