How to Water Sago Palm (Cycad) Once Each Week in the Winter

Q. Now that our irrigation is only allowed for 1 day, I was wondering if once a week is sufficient watering for my small sago palm. Should I hand water it on other days?

Not the readers sago palm (cycad) but it is small! It is in a container so it is more difficult to water than one planted in the ground. The soil in the container is more limited in size than one planted in the ground.

A. Hard to say. Depends on how much water your soil around the sago palm holds, where the drip emitters for it are located and the side of the house it’s on.

Hard to believe this cycad, or sago palm, is growing in Las Vegas. It was situated in the right location with the right care.

           Ideally the drip emitters are located between 12 to 18 inches from the trunk. For large sago palms I would suggest three emitters spaced in a triangle. Run the irrigation system long enough to water 12 to 18 inches deep. you can measure that with something long skinny and hard like a piece of rebar. If the sago palm is smaller, it may need only two emitters to wet the soil to the same depth. Smaller plants don't use as much water, but the system needs to run just as long.

Hard to accept this is the same plant as the one above. But this one is located in the heat of the sun and growing in poor soils.

           Plants on the south and west sides of the house or wall use more water faster than those on the east and north sides. A deep watering once a week should be all that is necessary for them in most soils and locations except the hottest.

Pines and Eucalyptus With no Water Growing in the Desert

Q. I have pines and eucalyptus that are not being irrigated at all. There is no irrigation applied but these trees are tall and healthy. What gives?

This eucalyptus has on applied irrigation in the desert. Sometimes trees can access underground water and survive.

A. Trees need water to survive. And large trees need more water than smaller ones. Some trees like your eucalyptus and many pines can grow deep roots. But trees need a minimum amount of water, or they won’t thrive otherwise deserts would be filled with tall, healthy trees like yours. They are getting water from somewhere.

Large trees use more water than smaller trees. Such is the case when the water was turned off to this mulberry.

           Plants are lazy, like us. Tree roots take up water where its easiest to survive. If they want to reproduce, then they need more than enough to survive. If the deep water is easiest to follow, then it will use it, if their roots can reach it.

           Tree roots don’t “seek” water in dry soil. They chase it. They “sense” water is there (compared to dry soil surrounding their roots) and grow best where water (and air) are abundant. If it can get lots of shallow water, like growing in a lawn, then that’s where tree roots grow abundantly as long as they can get air as well. If the water is deep, then that’s where roots grow if the soil is moist often enough to attract tree roots and they can “breathe”.

           Established pine trees grew “without water” at the El Rancho on the Las Vegas Strip after its fire. The property was abandoned, and the irrigation was turned off as well. Pine trees had to survive on only the deep salty water that their roots could get several feet below the Strip. This available water used to be considered a “nuisance” until developers saw its value in the desert. As Mark Twain used to say, “Whiskey is for drinking; water is for fighting over.”

           Both established pine trees and many eucalyptus have the potential to develop deep roots if given a chance and find a deep source of water.

Leaf Miner in Lemon Leaves

Q. My potted Myer lemon tree has “wrinkles” on the leaves. The nursery told me that the leaves have an insect living inside the leaves.  I used whatever product was sold to me last spring and the leaves still look wrinkled. This is my second year having the tree and it has 12 lemons on it.

Leaf miners on Myer lemon is usually a "greenhouse problem" with warmer temperatures.

A. The nursery was right. The leaves of your Myer lemon have leaf miners inside of them. But the product you were using was wrong. Leaf miners are usually small flies that lays eggs on the surface of the leaves. these eggs hatch and the “maggot” of this fly tunnels between the outer surfaces of the leaves. Previous to yours, the only place I ever saw leaf miner on Myer lemon were in another country grown inside a plastic tunnel they called a “greenhouse”.

Leaf miner infestation of tree leaves of Myer lemon is usually a greenhouse problem but here it was growing in a container. By the way, Myer lemon is a bit too large for container growing unless you use a very big container.

           There is no insecticide I would use to control them. The usual method used is to hand remove or pick the infested leaves and immediately destroy them.  Leaf miners found inside tree leaves are usually a minor problem when growing citrus. Their life cycle can be easily interrupted by removing infested leaves. Leaf miners are more of a problem in leafy greens like spinach and lettuce. 

A word of caution. These leaves must be destroyed soon after they are removed, or the leaf miner insect will emerge, mate and continue to infest other leaves.

           I guess if you were to use an insecticide for controlling leaf miner then I would spray a systemic insecticide like imidacloprid if it is labeled for food crops. But in your case the easier and safer method is to remove infested leaves and immediately destroy them and interrupt the insect’s lifecycle.

Palo Verde 'Desert Museum' Will Recover from Wind Damage

Q. I have a desert museum Palo Verde that was damaged during a windstorm. One of the branches blew off and damaged the trunk. It is an eyesore. Should I replace it?

Replacing a tree because of damage is a personal call. The tree will repair itself from that kind of damage. It may take three or four years if you can live with that kind of damage for the next year or two.

A. I would let the tree heal on its own but help it along its way. Healing takes two to three years if the tree is kept in good health. To do that, clean up the wound and apply management practices that encourage it to heal. Don't use any paint or “tree healer” as this was proven ineffective in past research and could actually slow the healing process. If you do paint the damaged area, use latex water-based paint. If there are any “splinters” resulting from the damage, remove them with a sanitized knife. Make the damage, and healthy areas surrounding it, as smooth as possible so the healing is faster and pleasant to look at.

Large tree wounds will heal if given time and you provide adequate water and fertilizer.  First they will compartmentalize their wounds and then start rolling in their cambium layer as it heals from site.

With that same knife remove the outer bark so that the edge is smooth and clean, and the damaged area is shaped like a vertical football. The damaged area will “compartmentalize” and the tree will “roll” over the area as it heals over the next couple of years. When the tree starts to grow this spring, make sure it gets adequate amounts of water and fertilizer. Good health practices help the tree to heal faster.

Early or late snowfall can damage trees with leaves still on them as this African sumac was damaged in Las Vegas. Repair of split limbs must be done very soon after the damage occurs or it won't work.

To reattach or repair a limb split, or otherwise damaged area from a tree during a windstorm, is usually a lost cause. If done successfully the limb must be reattached, or repaired, within minutes or even seconds after it is severed or broken. Time is very important so that the damaged area doesn’t “dry out” before it is repaired.

Century Plant (American Agave) Not Growing Well

Q. We have a century plant thriving over the past 10-12 years in our front yard. Towards the end of summer, we noticed lower leaves getting soft and tender, leathery even, eventually turning yellow. No new shoots are visible emerging from the core. It gets watered occasionally.

Century plant or American agave. A magnet for agave weevils.

A. Century plant is an agave weevil magnet! My guess is that's the problem. The only method I know to control agave weevil is to apply an insecticide around the base of all agaves in March or April of every spring. The insecticide is used to protect the plant from spring infestations. Sprinkle a granular insecticide at the base of the plant and lightly water it. The other option is possibly to drench the soil immediately around the agave with systemic such as imidacloprid (if the label permits). 

Warning sign of American agave that it might have agave weevils. Apply granular insecticide in the spring as a prophylactic treatment.

            The adult weevils have wings and can fly. They can fly from a neighbor’s plants to a different neighbor’s landscape. These adult beetles lay their eggs in the crotches of the agave in the spring. They don't use calendars but fly during the spring when it's perfect weather. That is why the timing for an application is sometime “in the spring”. The “grubs” hatch from the eggs and tunnel inside the core of many different types of agaves and cause their tunneling damage. Sometimes the damage is so severe it kills the plants outright or it might cause a smaller problem when plants are larger.

This is the type of problem agave weevil can do on established plants. Notice the base was rotten and the plant "collapsed".

            The other usual problem is watering too often. This can weaken or kill the plant. It doesn’t sound like that is your problem. I would caution you to water the plants deeply and not just a sprinkle them with a hose. Depending on the size of the agave it can take from 5 to 15 gallons of water varying from a small to a large American agave. If the American agave is large, then use three drip emitters located about 12 to 18 inches from the plant in a triangular spacing and watch for signs of stress. Apply water about three to six weeks apart during the summer.