Soil consistency in landscape makes irrigation easier

Q: I was reading your article and posts on your blog about planting trees and shrubs now. You recommended either adding compost to the soil taken from the planting hole or adding a totally new soil mix when planting. Which soil do you recommend for planting trees and shrubs?

A: Whichever you chose to use, either adding compost to the existing soil at planting or bringing in a totally different soil mix, make sure the soil is as consistent as possible throughout the landscape and in each planting hole. Making the soil the same when planting makes knowing when to irrigate much easier to figure out and schedule.

The soil used around trees and shrubs when planting doesn’t have to be identical to what is there already, but it should be close. The only difference is that this new soil used for planting is enriched with compost so root growth and establishment of these plants is as quick as possible before it gets cold.

Tree and shrub root growth happens rapidly in warm soils (60 to 70 degrees) but slows down considerably as soils get colder (45 to 55 degrees). Root growth and the establishment of trees from cold climates (peach, apricot and apple, for instance) may be OK at the lower temperatures, but plants from warmer climates (like most citrus) won’t generally establish as quickly.

I am suggesting that planting of trees and shrubs should end no later than mid-November. Planting from December through mid-January delays how quickly these plants will become established. It doesn’t mean they will fail, but these low temperatures will slow down root growth and chances of failure increase.

Q: We noticed that some of our pomegranate seeds are not turning red. They are clear or white, but they still have a semi-sweet flavor. Do you know what could be the problem?

A: Not all pomegranates have the same aril color (seed color). Some pomegranate arils are red, some off white, some arils are sweet and some are puckery. Some pomegranates are “soft seeded,” meaning you can chew or swallow the seeds inside the arils, while some have hard seeds you must spit out.

Some pomegranates also have white rinds (outer skin covering the whole fruit), some yellow, some red, some purple or almost black and some are red streaked with white or yellow. Pomegranates are unique unto their own variety. Some examples of pomegranates include varieties like Wonderful, Sweet, Sharps Velvet, Parfianka and Pink Satin.

Sounds like the variety you have is the Utah Sweet variety (a selection from the variety Sweet), which ripens in late September or early October, is sweeter to the taste than some other varieties, has soft seeds so you can swallow or chew them and has an outer rind not dark red (like Wonderful) but reddish and oftentimes with yellow streaks.

The fruit of Utah Sweet is not pretty like Wonderful but is sweeter (less puckery) and the seeds are chewable. The Wonderful variety is red inside and out, puckery in flavor, and ready for harvesting later, about Halloween.

Q: I’m following my local water district’s watering schedule suggested for lawns in my new desert landscape but will reduce how often water is applied as the new plants become established. Both the sago palm and the bay laurel are on the same valve as my desert plants. Are the number of gallons you recommended appropriate for this frequency of watering? Or does the amount per application need to be adjusted?

A: I am not sure what you mean by desert plants and desert landscaping. Most people think that if the landscape is covered in rock that this qualifies it as a desert landscape. Any plants growing in it are, therefore, desert plants. Covering the surface of the soil does not qualify any landscape to magically become a desert landscape.

Furthermore, plants growing in a desert landscape do not automatically become desert plants. Desert plants originate from desert climates like the Sonoran, Chihuahuan and Mojave deserts. True desert plants are appropriately called “xeric” and use far less water than other plants found in desert landscapes.

How often water from one valve is turned on is determined by the plant most desperate for water. All other plants on the same valve — desert plants or not — get water whether they need it or not. Both sago palm and bay laurel are not desert plants, and they will determine when to water if planted with true desert plants.

Unfortunately, most plants planted in desert landscapes are not really desert plants and start failing beginning four to five years after planting.

Apply water to at least half the area under the plant canopy. The water applied to sago palm should wet the roots to 18 inches deep with few additional drip emitters needed. The water applied to bay laurel should wet the roots a little deeper and to a wider area under the canopy as it gets bigger.

Q: During the spring, I put lawn insect killer to kill the grubs my lawn gets every year. The lawn still keeps dying. So, I put fungus control on twice during the summer months. Brown spots in the lawn get bigger and in some areas turn the whole lawn brown. I checked the sprinklers and every area is getting 15 minutes of water in the early morning six days a week. What should I do?

A: In our desert, the main reasons why brown spots happen in lawns are in this order: irrigation, management, diseases and lastly insects. Just because a lawn is getting water from a sprinkler and wets the grass does not mean the water is applied to the lawn evenly. Use a length of rebar pushed into the soil in brown areas to make sure the roots of the lawn are wetted to a depth of 8 to 12 inches after an irrigation.

Punch holes in the lawns in the spring once a year to improve the lawn’s health and its disease resistance. Gasoline-driven aerators punch holes in the lawn 4 inches deep and help roots grow deeper. Deeper roots improve the health and resistance of a lawn to heat.

Mow the grass as tall as possible. I noticed many maintenance companies mow tall fescue too short in this town. Fescue should be mowed at the highest setting on a mower. Taller grass means deeper roots. Deeper roots mean better tolerance to heat.

Lawn diseases in the desert occur in July and August. Seldom are diseases a problem at cooler times of the year. To help prevent lawn diseases, raise the mowing height and clean the mower blades if used on another lawn so lawn diseases are not transferred from place to place.

The last resort is the use of chemicals for controlling insects and disease. Do these other things first.

Q: Is it natural that leaves are turning yellow on 1-year-old pear trees?

A: It’s never normal for any plant, except plants bred to grow yellow leaves, to have yellow leaves this early in the fall. Something is wrong.

First, pull any mulch away from the trunk or main stem 6 to 12 inches. Make sure you see bare soil in this area.

Next, check the planting depth of the tree. Make sure that no more than ½-inch of soil is touching the trunk. The tree should be planted the same depth it was growing in its container. If deeper than this, pull the soil away from the trunk and replant the tree at the right depth when temperatures cool down.

Finally, add your favorite iron chelate to a bucket of water and use this solution to water the tree in late January of next year.

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.