How do you feel when you have been exercising regularly and eating correctly? You are bulletproof, right? Doesn’t it also make sense that plants will be the same?
When plants are at their healthiest, strong and most resilient, they can better resist the high temperatures and, to a lesser degree, even the low temperatures that surround them. Plants recover from stress more quickly when healthy. Plants are no different than us in that regard.
During these past two weeks, nearly all the plant problems submitted to me were either because of the summer heat, plant location in the landscape, improper planting technique or combinations. If the landscape planting spot was chosen correctly, the use of poor quality compost mixed in the soil, or too little or no compost used at all when planting, was the second reason.
If you follow me and my internet blog, Xtremehorticulture of the Desert, or my podcast, “Desert Horticulture,” I discuss a lot about planting techniques and how important it is to use a good quality compost mixed into the backfill at planting time.
As the Dust Bowl days of the 1930s showed us, it is not enough to give plants only fertilizer and water. Plants need a healthy soil environment as well because, unlike us, they cannot move to a less stressful location when facing adverse conditions. They must stay put and either look good, survive or die.
This is why it’s so important to first find a good place in the landscape where your plant can grow to its full potential, not just survive. Secondly, plant it correctly so this plant can withstand our harsh environment.
After finding the best location in your landscape for this plant, improve the soil so the roots can explore their new home. As I have always said, the best compost to use when amending landscape soil is the one made at home.
I understand that sometimes life gets in the way and we cannot always make high-quality compost at home. The second-best compost to use is a rich compost that you can buy in bulk or in bags. Getting the landscape plant starting off on the right foot can last a long time after planting.
The correct amount of compost mixed into the surrounding soil when planting is 25 to 30 percent of the backfill. That is between one part compost to two or three parts of your landscape soil.
Is there research that tells you not to use anything? Yes, but this research is wrong for our part of the desert.
Q: A Red Push pistache tree was planted in my yard last week. Unfortunately, it received some damage along the way. A 6-inch strip of bark is missing, oozing sap, and several branches were cracked and stripped of vegetation. The stake supporting the tree is cracked in two locations, one next to the damaged bark. Obviously, it was planted poorly. Should I be concerned? What steps should I take to prevent long-term issues?
A: In my opinion, either the tree needs to be replaced or there should be some compensation for the damage. There is a risk involved in accepting damaged plants.
I understand that some nurseries or garden centers have a replacement policy if a plant dies, but that does not give license for tree abuse. To me, that shows disrespect.
If damage to this tree occurred prior to the nursery receiving it, then the nursery should have rejected the tree upon inspection when it was received. If the tree was damaged during transport to the landscape site, then the damaged tree should be rejected prior to planting. If the tree was damaged when it was planted, the tree should be rejected and replaced, or compensation should occur to the homeowner.
In the long run, a 6-inch strip of bark missing from the tree should not hurt its establishment. Healing this injury will cause a delay in tree establishment but, more importantly, provide an entry point for disease or insects, in particular crown gall disease.
Crown gall disease is a bacterial disease caused by injury to plants from tools that were dirtied by the soil and then used for planting. Crown gall disease is common among landscape plants that were damaged during planting. It is very important to not injure plants during planting.
I have seen several instances of crown gall disease here in Las Vegas, and it always starts because of plant damage. The disease is not lethal but causes a cancer-like growth to occur where the plant was damaged. It can slow the growth of the tree and cause future problems and possible removal later.
If it were me, I would reject the tree because of this damage and have it replaced.
Q: When can I fertilize my newly planted Podocarpus maki shrub. They are now 3 feet tall.
A: Podocarpus maki is a dwarf evergreen (all green) shrub, commonly called the dwarf form of a yew plum pine or Buddhist pine. The common form of Podocarpus can get 50 feet tall, a huge plant, but the maki version grows slowly to only about 6 to 8 feet tall. It should be planted so it gets some afternoon shade, probably on the east or north side of a home or privacy wall.
A starter fertilizer should have been used at planting time, but a rich compost mixed in the backfill will also work and no additional fertilizer is needed. High phosphorus from a fertilizer like 16-20-0 or rich compost helps establish this small dwarf tree. Although this plant is considered mesic, it is fairly drought tolerant and resists soil salts.
A single annual application of a tree and shrub fertilizer to the soil and watered in will help its growth when applied in February. If the plant is looking a little peaked now, lightly apply a granular landscape fertilizer to the soil in October and water it in. After it has been planted, and since you are not promoting flower growth but leaf growth instead, any lawn fertilizer low in phosphorus will work as well.
Q: Your article fits right in with my concern for our 15-year-old Joshua tree. I only water the tree two or three times in the summer — very deep watering.
A: That’s perfect. I wish others would get your feel for it. True Mojave Desert plants like the Joshua tree don’t need to be watered often. But when they are watered these plants need to be watered deep and wide. Just like rainfall.
Obviously, your Joshua tree cannot be watered with an irrigation clock but rather by hand. A stationary sprinkler on the end of a hose and the water adjusted so that it applies water about 6 to 8 feet in diameter will work.
Finally, use a long piece of rebar to adjust the time needed to get the water deep enough. Pushing a thin piece of steel so that it slides into wet soil easily to a watering depth of about two feet deep is enough. Using a piece of rebar will tell you the minutes needed to let the water irrigate the Joshua tree deep enough.
Watering only two or three times each summer, once in the early spring, keeps Bermuda grass invasion under control and gives Joshua tree enough water to push the new green growth in the spring.
Q: Today I found handfuls of grubs in the soil surrounding several plants that are struggling and in the holes of plants that died over the summer. For all I know, they are everywhere in large quantities and have been in my garden for years. My question is what have I done to make my garden so welcoming?
A: Grubs are immature forms (juveniles) of mostly scarab-type beetles (adults). They turn into adult beetles once a year and do not persist year to year.
However, the female adult beetle will lay her eggs for her next year’s offspring near plants that she likes and is growing well. These baby grubs hatch, dig into the soil and feed on plant roots.
Grubs that eat plant roots are usually from any of the so-called June beetles. These June beetles do not have to be brown, but they can also be iridescent green or striped. The female adult beetles lay their eggs where their favored plants are doing great.
The presence of grubs in your yard is a back-handed compliment in a way. The adult female beetle probably would not have chosen your yard if the plants weren’t doing as well.
Not much you can do about attracting them less but if you can pinpoint which plants are attracting the most and get rid of those plants it would help. Otherwise, you are stuck using pesticides as a soil drench when you have discovered them feeding on the roots of their favorite plants.
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.