Do you want to grow roses in your landscape? If you want to know which rose varieties have been successful in our hot desert climate and how to plant and manage them correctly, attend the annual South Valley Rose Show on Nov. 9 at the University of Nevada Cooperative Extension offices just south of the airport on the corner of Windmill Lane and Paradise Road. Rosarians will be present to answer questions about growing roses in our hot desert climate and poor soils from 1 to 4 p.m. For more information, call the master gardener help line at 702-257-5555.
Q: I just planted a 5-gallon mesquite tree following your advice and was wondering how I should stake it. Also, I was wondering if I should use the deep watering stakes recommended for it? They are plastic, 2 feet long with holes drilled in it for deep watering and supposed to encourage deep rooting of trees.
A: If the planting hole is dug wide enough and if the soil used when planting is amended with something decent, then these deep watering tubes are not necessary. If you water your tree deeply, and not daily, the tree does not need them. If you water your whole yard daily including your trees, which I don’t recommend, then maybe there is some benefit using them.
I have not listened to the sales pitch for these, but I would guess they are marketed to prevent shallow roots from growing on the soil surface. Most trees don’t want their roots on the soil surface. They want their roots to grow deeply for better anchorage in the soil and access to a larger amount of water. Small trees should have soil amended to a depth of 18 inches, medium height trees to a depth of 24 inches and tall trees, like most of our pines, to 36 inches.
Root depth of trees is controlled by three factors: if tree roots normally grow shallow, condition and type of soil, and how the tree is watered. These watering stakes focus only on the third factor. Control root depth with soil amendments and water management. Trees and large shrubs should be watered separately from shallow-rooted plants like lawns, flowers and vegetables.
Some trees like mulberry and many types of ash have a preponderance of shallow roots. It’s normal for them. It is part of their genetics and the environment where they came from. In some cases, these roots can be removed from the soil surface or covered with mulch.
Some trees grow roots near the surface of the soil where roots can access air better. This happens in heavy clay soils or soils where the planting holes were not dug or prepared well. With heavy clay soils, it is best to grow trees on a 12 to 18-inch rise or mound so the soil can drain, roots can breathe and have somewhere to grow.
Always dig the planting hole at least three times the size of its container and amend this soil with decent compost at the time of planting. Buy these tubes only if needed.
If the tree is from a 5-gallon container, then it might not need staking. Trees planted from larger containers probably need it. The primary purpose of staking is to keep the roots from moving. Movement of the upper trunk and limbs is a good thing.
Q: You mentioned on your blog that chelated iron won’t green up yellow leaves when it’s applied to the soil outside of the spring months. Why does this happen? We are a major tree company and see this sometimes. Also, how long should it take to see leaves become green again after we treat the tree with iron?
A: Two methods are used here to green up yellow leaves. It has a lot to do with the chemistry of the soil — more specifically how alkaline it is, whether it is an iron problem and the type of chelate used in the iron fertilizer. It can get hard to predict if it will work or not. I will sometimes “shotgun” the leaves if I am confident the yellowing is because of iron and the problem can be corrected.
If I have the time, I will start with a spray bottle of iron fertilizer to see if an iron application will work. Spraying this liquid mixture on yellow leaves will tell me if the yellowing is from iron or not. But it takes about 24 hours to find out.
If the leaves change to a darker green in 24 hours, then an iron fertilizer application will work. Otherwise, it’s a guessing game. For some people, 24 hours is too long to wait for an answer.
Here’s where it can get tricky. If it is early enough in the year and the tree is still producing new leaves, I can apply an iron fertilizer to the soil, and it should work. If it is later in the growing season and the tree has, for the most part, stopped growing and preparing for next year’s growth, then the only thing that will work is spraying the leaves with a liquid iron fertilizer.
If an iron fertilizer is applied to the soil, then the choice of iron fertilizer to use can become critical. If the soil is in rough shape and neglected, then use an iron fertilizer containing the chelate EDDHA. I would, in fact, use that iron chelate fertilizer whenever trees and shrubs are surrounded by rock.
Because that can be a guessing game, I only recommend iron fertilizers that contain the EDDHA iron chelate. It’s more expensive, but I am more confident it will work under most circumstances.
If the soil is in good condition, then usually any iron fertilizer containing an iron chelate should work. If you are price sensitive and always buy the least expensive product then, because of the soil chemistry, your selection might or might not work. I understand the reasoning, but it is a gamble. Sometimes you win, sometimes you lose.
If you see leaf yellowing about halfway through the year or later, then soil applications won’t usually work. You must spray the leaves with a liquid iron fertilizer to cause the leaves to change from yellow to green. That can mean multiple applications of an iron spray. Please read my directions on how to make liquid iron applications to the leaves on my blog to improve your chances of success.
What to do? I usually do both treatments, shotgun it if there is a problem and I want the best chance of success. Two applications can be cheap insurance. If spraying works, it will cause the leaves to turn green overnight. Soil applications might take up to a week to see a change in leaf color and then it will be only in the new growth.
But applying the right iron fertilizer before the leaves come out in late winter or early spring can pay some dividends if you suspect leaf yellowing might occur.
Q: Is it possible to mix Kentucky bluegrass, ryegrass and Bermuda for year-round greenery and thickness in a lawn?
A: The short answer is no. But if you are satisfied with a hodge-podge for a lawn that will slowly change over to Bermuda grass in full sun, or where irrigation is weak, then this combo is fine. It depends on the level of quality you are willing to accept in a lawn. Most people want a beautiful lawn, and this approach will not produce a beautiful lawn.
I understand the temptation. Our valley and the Mojave Desert lie in what is called the transition zone for grasses used for lawns in the U.S. The transition zone in Southern Nevada is not too cold for warm-season grasses like Bermuda grass and not too hot for the heat-tolerant Kentucky bluegrasses, perennial ryegrasses and tall fescue. The transition zone is a perfect place to grow all the grasses but grow them poorly.
The grasses are not managed the same either. Common Bermuda grass can be mown less than an inch, hybrid Bermuda grass less than half an inch. But Kentucky bluegrass and tall fescue should be mown at least 2 inches tall. Perennial ryegrass has the most versatile mowing height because it can be mown as low as hybrid Bermuda or as tall as bluegrass or fescue. Your selection of a mowing height will favor grasses that grow best at those heights.
The winter months favor the cool-season grasses like bluegrass, ryegrass and fescues. The summer months favor the warm season grasses like Bermuda. But Bermuda grass is aggressive and will choke out other grasses unless you do something about it. That will require work and money on your part.
Golf courses in Las Vegas were pioneers in using a mix of hybrid Bermuda and heat-tolerant perennial ryegrass together during the 1990s. But this mixture was managed yearly. If it weren’t, the Bermuda grass would take over. The Bermuda grass was thinned out, and heat-tolerant perennial ryegrass, like Palmer and Prelude varieties, were sown back into it in the fall. These management practices guaranteed a solid stand of Bermuda and rye during the summer months.
Bob Morris is 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.