Q: The top ring of sago palmfronds died after I transplanted it but remain on the plant. I left this brown ring of fronds around the crown of the plant and it looks like new growth coming from the center is OK. Should I trim off the dead fronds without disturbing the crown or just let them fall off?
A: That’s an aesthetic decision more than a plant health decision. I can’t think of a reason why removal of dead fronds would affect the plant one way or another. Someone might raise the possibility of disease problems, but I don’t know of any.
Another option is to paint the fronds green with one of the green plant paints or dyes used for lawns and make the dead brown fronds appear green and alive. Or just remove them. There are several paints or dyes on the market.
Personally, I would cut them off and let the growth from the center take over as it emerges this spring and in the following years. Remove the dead fronds to within about a half-inch or less of that center crown. The brown, dead fronds will probably stay there for several years or until they’re removed. But that’s my call on your situation.
Q: What’s wrong with my plants? The leaves are all yellow and starting to burn up.
A: I couldn’t see exactly from your pictures, but the plants appear to be either photinia or mock orange. Regardless, I bet they were planted about five years ago and the soil was covered with rock. Desert landscaping without using desert plants leads to problems in a few years.
Mock orange originally came out of Japan and Korea, and photinia came out of nondesert areas in China. However, both plants are very adaptable to different climates, and that’s a reason they are used in many places, including here.
However, nondesert plants will struggle in desert soils, so the soils need to be improved at planting and under constant improvement as these plants get older. Yes, they look good for about five years after planting in amended desert soil, but when they are incorporated into desert landscaping surrounded by rock and not maintained properly, they don’t do as well when the organics eventually disappear from the soil.
The cause of the yellowing is a combination of soil reverting to its desert chemistry and suffocation of plant roots. Amended desert soil covered in rock becomes desert soil again in three to five years. The time difference, I think, depends on how much amendment was added to the soil and what kind was used.
Unless you plant desert plants in desert landscapes and cover the soil and rock mulch, many start to decline in a few years. Photinia and mock orange are two that will.
What to do? You can try the Band-Aid approaches and spray them with iron foliar fertilizers multiple times each year. You can apply iron chelate fertilizer, called iron EDDHA, each January. You can spread some sulfur soil amendment and see if you can adjust the soil alkalinity so the iron already in the soil is available to the plants. Or you can replace these yellow plants with desert plants that can tolerate desert soils, our climate and the rock mulch.
There are several lists of desert plants used in landscaping in the desert southwest and Las Vegas that can be found on the internet, and I will post a list of desert plans on my blog. Consult these lists and go to your local nursery and see if you can find some that will fit your situation.
Q: I have a cactus I bought as a start from a little nursery in 29 Palms that grew a foot a year for the last 15 years. It finally tore out of the ground and fell over, causing the ground to quake. It towered to 17 feet and was spectacular. The cactus had no water supply but was irrigated by water runoff from the roof.
A: I suspect the cactus had a very small, spreading root system that finally just couldn’t support it anymore and it fell over because it was top-heavy. Cacti and other desert plants have extensive, relatively shallow roots that spread as much as eight times their height. This extensive root system provides a very efficient way of gathering sparse rainwater and provides substantial support for taller cacti.
Nondesert plants, sometimes referred to as “mesic” trees and plants, are reported to have spreading roots as much as two to three times their height. That’s still quite extensive, but not like desert plants.
Cacti have more extensive roots that are not terribly deep for gathering sparse rainwater as quickly as possible. Desert plants convert this unexpected water into rapid growth and flowers. They are good at that.
So I think it’s important to periodically irrigate cacti large distances from the mother plant as they get taller. Plants get water where it’s easiest to find. Desert plants are opportunists. By that I mean when water is present, they grow quickly and then shut down when water is no longer available.
When these plants are watered close to their base, they tend to fall over as they get taller because the small roots can’t support its massive top growth. When they are irrigated, water should be applied over a large area.
Plant roots don’t actively seek water but grow toward sources of applied water because of soil moisture. With cacti and many of the other succulents, it doesn’t take much soil moisture to get them growing in its direction.
I think it’s beneficial to use a hose and hose-end sprayer periodically and spray the surface of the soil around cacti to get their roots spreading outwardly and anchor them in the soil as they become larger. Of course, water should be applied at times of the year or in intervals that don’t encourage Bermuda grass growth, a terrible scourge to landscapes.
Q: I transplanted a dozen rosemary plants from the planter in front of my house into pots to see if I could salvage them. I know rosemary likes full sun, but I’m curious if they could use some shade because of the shock of transplanting?
A: Yes, you should shade plants in containers after removing them from the planter, but you should also severely cut them back. Let me explain.
The general rule of thumb when you transplant any plant from the ground to a new location, including containers, is to cut back the top about one-third. In other words, reduce the amount of top growth the plant has because it loses so much of its roots during transplanting.
I’ve read estimates that as much as 80 percent of the roots remain in the ground when moving plants to a new location. The older the plant, the more roots remain in the ground.
If the plant is watered with drip irrigation, the roots grow closer to the plant and transplanting is more successful. For these reasons, and in my own personal experiences, when plants are more than three or four years in the ground, the chances of successfully moving them to a new location are reduced. Root pruning helps.
Transplanting plants from the ground to a new location or container is more successful if you can plan a year in advance. One year ahead of moving it, cut the roots with a sharp shovel as deeply as possible where you’ll be digging the following year. Root pruning causes roots to grow closer to the mother plant and improves the chance of transplanting.
If moving a plant into a container, put it in the shade the first growing season before moving it into intense sunlight. Remove one-third of the top by eliminating entire branches rather than cutting these branches into a “butch haircut.”
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.