No sunlight causes Canary Island palm fronds to die

Q: My Canary Island palm tree has black spots next to the spines on the fronds. Otherwise, it looks healthy. Is this something I should be worried about?

A: Canary Island date palms are slow-growing palm trees that can eventually grow 40 to 50 feet tall, tolerant of winter temperatures below 20 degrees as well as high temperatures. Their fronds can reach 10 to 15 feet in length so they are not a very good choice for moderate to small landscapes. Once established and they start showing some growth, they can handle a little bit of drought.

It’s best to water them like any landscape tree; water them frequently when getting them established and then, as they become established, occasionally but deeply when the soil starts to dry out. Water should be applied to at least half the area under the canopy of the palm tree.

Browning of fronds is typical to those toward the bottom that are beginning to die and need to be removed. These palm trees have a big head that produces heavy shade so it’s possible that the lower fronds may die due to a lack of light.

If the lower fronds are dying, the palm tree needs to be pruned. If these are fronds that get plenty of light, then the tree has a problem.

In new neighborhoods with soil that’s never been watered it’s possible this tree could have a nutrient deficiency. Make sure that the soil is amended with compost at the time of planting and that you are fertilizing this palm tree once a year with a palm type of fertilizer. This palm is notorious for potassium and magnesium deficiencies so make sure that the palm fertilizer you use is rich in both potassium and magnesium.

I found a fact sheet on Canary Island palms from the University of Florida. Remember it’s from Florida but it has some information, such as the presence of nutrient deficiencies, appropriate for the desert as well.

Q: I have five large cactuses. Three of them, which receive partial sun, grow paddles. The other two are in full sun. One of them rarely produces a paddle and no flowers. The other one produces flowers and seed pods every year but no paddles. This year I have five flower pods growing on this plant. I water and fertilize all of them. Any idea why the cactus produces flowers and no paddles.

A: All the Opuntia-type cactuses (e.g., beavertail, bunny ears or paddle type) come from either the drier areas of central or northern South America. They are native to this area of the world, and some can grow to 20 feet. When I have grown Opuntia-type cactuses, they did not start flowering until they got 2 to 3 feet tall. Their smaller size may be part of your concern.

It’s counterintuitive, but many cactuses prefer to grow in soils that have been amended lightly with compost or manure. Not a lot, but they prefer slightly amended soils. To get them to start producing and growing, I fertilize them with a high nitrogen fertilizer once a year in early spring just prior to new growth.

To push new growth, I irrigate 2 feet deep once every three weeks with water applied to an area about 3 feet from the cacti in all directions. Shriveling of the skin of these types of cactuses tells you that they need water. They shrink because the stems store internal water. After an irrigation, the stems and pads swell up so the wrinkles disappear, push new growth for two or three weeks and then start to shrivel again when the soil begins to dry out in the summer.

All the Opuntia cactuses need at least eight hours of sunlight every day to flower and grow.

Q: Our oak tree in our backyard has a damaged trunk and is not growing well. Our gardener suggested hiring an arborist to treat the tree. Can we purchase something to correct this and do it ourselves?

A: I looked at the pictures that you sent to me, and it looks like the trunk of your tree has been damaged. I am not sure what caused the damage, perhaps strong sunlight. With a little bit of TLC, you can encourage it to recover. It is an oak, so recovery will be a little slower than some of the faster-growing trees.

Judging from your picture, the tree is surrounded by rock. Rake this rock back a distance of 6 feet and make sure the tree roots are getting water in this area to help speed recovery. Trees up to about 10 feet in height will need about 30 gallons of water every time they are irrigated. As the tree gets larger, it will require more water. Most oak trees grow at least 40 feet in height.

Once the irrigation system has been installed, cover the irrigated area with a thin layer of compost about ½ inch thick. Fertilize the tree once a year in the very early spring by placing the fertilizer where it will dissolve and move to the roots.

If the tree has not been fertilized this year, do it now. The landscape rock is raked back to cover the area. It will take time but the tree surrounding the damaged area should start to roll over the damaged area by the end of the first year of growth.

Q: We have several palms in our yard that I planted 12 years ago in our landscape in Mesquite. The fronds recently started turning yellow at the center. They are not the normal dieback of the bottom fronds. They are watered by four 2-gallon drip emitters for each palm and are watered every other day in the hot summer months for one hour each time. I also use a palm fertilizer twice a year.

A: Since you are using a palm fertilizer, I don’t think it’s a micronutrient deficiency (potassium or magnesium) that’s causing the yellowing. It may, however, be a root problem.

To me, it sounds like a slow progression of root rot due to poor drainage. Root rot oftentimes causes the center of palm trees to yellow. This frequently happens when rock is used as a surface mulch and the plants are grown by themselves or isolated.

I don’t think that 8 gallons of water during the summer every other day is a lot. If you are going to water, give them a good drink of water and then hold off for the next cycle until the soil begins to dry.

When yellowing occurs at the top of the tree, then we should start looking for trunk or root damage. A lack of water would show up as a browning around the edge of the leaves or a top that doesn’t fully develop. I am curious whether the soil is draining enough after watering or the soil is draining to slowly.

If you want to keep the same frequency of irrigation, then plant the palm on top of a 12-inch tall mound of soil about 3 feet in diameter. Try using an inexpensive soil moisture meter to determine when to again water. A soil moisture meter should register around “5” when the next irrigation is applied.

Q: I had Texas laurel planted as a hedge in my yard since 1998 and have not trimmed it at all after planting. My unpruned Texas laurel acts as a privacy screen between the golf course and our pool. However, it blooms profusely, leaving the seed pods. Would the tree benefit from having the pods removed or is it best to leave them? Would I get more blooms if I trimmed off the pods?

A: Yours is a creative application for an evergreen water-efficient small tree. They should be planted about 8 to 10 feet apart to act as a privacy hedge. Yes, the pods can be removed, and yes, it will make more flowers but the trigger for flowering is mostly in the spring.

The primary reason for removing the pods is looks. Some people don’t like the looks of their pods. Some do. Make sure to apply a fertilizer like 16-16-16 once in the early spring to get more and bigger blooms and more growth. Also, reduce the number of main stems so each stem gets more food for growth.

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.