1st-time soil test establishes baseline for new homeowners

Soil tests are mostly about what fertilizers and soil amendments should be applied to get the desired yield. I was in the former Soviet Union years ago when a member of Parliament once asked me, “What is the maximum wheat yield in the United States?” I told him, “U.S. farmers don’t maximize yields. They maximize profits.” Soil tests help farmers maximize their profits.

Soil tests are primarily aimed at soil chemistry to aid a farmer’s profitability. Soil tests will not tell you why a plant died or what chemicals were added to the soil that killed a plant. An agricultural soil test won’t tell you that. Those tests can be done, however, but are much more expensive and require a consultant to guide you.

What good are soil tests to a homeowner and when should they be done? A serious gardener should submit a soil sample as soon as new property or growing area is purchased.

A first-time soil test establishes a baseline and tells you at the beginning what’s adequate about your soil chemistry and what’s missing. After that, a soil test is submitted by homeowners about every four or five years to make sure they are on track with their fertilizer and soil amendment applications.

Soil tests are a smaller sample of a larger soil sample taken from the top of the soil to the depth plant roots grow. Several smaller samples representing this depth are added together. A very clean 5-gallon bucket is used for mixing the larger soil sample so that a smaller sample — a pound or so — can be submitted for testing.

Expect results in about a week after they received your sample. If you’re having trouble interpreting them, hire a consultant the first time so that you are taught how to read them.

Q: I have a Canary date palm that developed yellowing leaves last year. I planted this palm about 10 years ago in my landscape.

A: The proper name is Canary Island date palm. Eliminate simple possibilities first: water and drainage. Make sure whatever method you are using to irrigate the tree has not changed because of a broken irrigation line or malfunctioning irrigation emitters. Check the soil around the tree to make sure it’s not still wet before it is irrigated the next time.

The soil at 4 or 5 inches deep should still be starting to dry when you water again. Watering cycles of palms are similar to other large trees on your property and not to other locations like lawns and flowerbeds that require frequent irrigation. Watering palm trees as frequently as you would in these locations would be a mistake.

Fertilize with a palm fertilizer. Palm nutrient deficiencies such as potassium, magnesium or manganese deficiencies can cause yellowing. Use a palm tree fertilizer such as Arizona’s Best the next time this palm tree is fertilized.

There are a couple of disease possibilities that have not yet, to my knowledge, been diagnosed in Southern Nevada. Three palm diseases have been noted in Southern California on this palm. The only disease which causes fronds to yellow on Canary Island date palm is fusarium wilt.

This disease can be spread from tree to tree through pruning tools. Wiping or spraying the cutting blades of pruning tools with at least 70 to 90 percent isopropyl alcohol will effectively keep the disease from being spread from a lack of sanitation to other palms.

Anyone pruning these palms should never use dirty tools. Tools should be cleaned with soap and water first and then sanitized before pruning begins.

Q: Do you have any idea why the leaves of my pear are browning and dying out? I’ve never seen anything like this.

A: I’m going to state the obvious. The leaves turned brown because they are dead or dying. I know you want to know why they are dead.

The usual reasons can be wide-ranging and related to either disease, damage to limbs or the trunk, or soil problems. The possibility that concerns me the most is a disease called fireblight. Search the internet or my blog for pictures of what fireblight disease looks like. Check the entire tree for this kind of damage.

If you are at all suspicious of fireblight, then prune out these branches 6 to 8 inches below this area, and use sanitized pruning shears. If more than one cut is needed, then sanitize your pruning shears between each cut. Use 70 percent isopropyl alcohol or higher or a cigarette lighter and heat up the blades to kill any possible disease organisms that you could transfer to the cuts.

Make sure the tree was planted with compost mixed into the soil as an amendment at planting time. Never surround fruit trees with rocks or gravel on the surface of the soil. Wood chips that can decompose and benefit the soil are much preferred over rocks for any kind of fruit tree.

If you are watering daily, the tree roots could be suffocating because the soil stays wet and not draining properly. Root suffocation also can cause the leaves to die and turn brown or black.

Stop daily watering. Water every other day or every third day during the heat of the summer. Apply enough water when irrigating to cover a large enough area under the tree to initially wet and keep this soil from totally drying out until the next watering.

Pear trees grow very well in our climate if the soil is prepared at the time of planting with compost and if the soil surface is covered in wood chips after planting. You should never have to water daily if you are giving the trees enough water, over a large enough area, when you are watering.

Q: We had a dwarf orange tree in a pot on the patio for about four years. It never bore any fruit during that time. This spring we replanted it into the ground, and bingo, tons of blossoms showed. However, sadly, no fruit. Any ideas?

A: A one-year difference could be coincidental. Citrus can be tricky because frequently they bloom during cold months when the possibility of freezing weather occurs. If there was freezing weather, it can selectively kill open flowers or young fruit causing them to abort without damaging leaves or stems.

Flowers dropping can also be caused by the soil in the container getting too dry. Not being watered, having the soil dry out, just for a few hours to a day can cause young fruit to drop.

The soil used for growing container plants needs to be replaced every three to five years because it wears out. In the cool fall or spring months, remove the tree from its pot, trim 1 inch of roots from all over the rootball, wash the roots and old soil out of the rootball and replant it using lots of water. Then it will be good for another three to five years.

Q: I have a 5-foot yucca tree that I cannot get to be disease-free after two years of trying. I have tried the following chemicals: Bayer Advanced Complete Insect Killer, Bonide Thuricide and Bonide Tree and Shrub Insect Control Systemic. Any suggestions on how to save it?

A: Judging from the picture you sent to me your yucca tree is Yucca gloriosa, aka Spanish dagger. Spanish dagger is going to get brown spots on its leaves that resemble disease, but it is either planted in the wrong location or planted incorrectly or both. This plant is both mesic (high in its water use) and not a desert native.

Spanish dagger is an eastern coastal native from South Carolina to Florida. If planted in our desert Southwest, this yucca will look diseased if it’s planted on the west or south sides of a home, surrounded by rock or watered like a cactus.

Because it’s a native of the southeastern United States, Spanish dagger should be planted so that it gets shade in the afternoon: on the east or north side of a home landscape in afternoon shade. Also, plant it with compost amending the soil and surrounded by other mesic plants to help moisten the soil.

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.