Not all weed killers will eradicate palm seedlings

Q: We had thousands of “blades” pop up all over our yard over the past several months. They look like giant blades of grass. We’ve pulled tons of these out of my flower beds.

A: Those are palm seedlings. A nearby palm tree has dropped seeds and they are sprouting probably after rain or irrigation.

Pulling them may not work well unless the soil is very wet, but if you use a dandelion removal tool or asparagus knife they can be cut and removed easily. The seeds are not very deep. Cutting them with this tool about an inch below ground will get rid of them.

Many weed killers will not kill palm seedlings. To kill these plants requires weed killers that also kill other woody plants. Roundup sprayed on the leaves is not very effective because it is principally a grass killer, and palm leaves repel foliar sprays.

Your best bet regarding weed killers is to use products that also kill other woody-type weeds such as oxalis, also called wood sorrel, and clover. These types of weed killers should give good control if mixed with a wetting agent (detergent) and sprayed on the plants several times over a period of a few weeks.

Q: My Australian bottle tree in the middle of my yard has some leaves turning brown and shedding. Is this normal?

A: No, it’s not normal. This frequently indicates it’s not getting enough water. Make sure you are not watering daily because this can cause other problems. Watering once or twice a week should be enough but make sure the volume of water applied surrounds the tree and moistens the soil to a depth of 2 to 3 feet.

Make sure there are enough drip emitters to support the water needed for your tree during the time they are running. As trees get older and bigger, add more emitters because they will need more water. The frequency of application doesn’t need to change. Only the amount of water applied.

For now, place a hose near your tree and put a sprinkler at its base. Lightly apply water once a week for several hours and see if the tree perks up in a couple of weeks.

Another method for deep watering is to use a device like a Ross root feeder. Push it into the soil at several locations, 2 or 3 feet from the trunk. Inject water into the soil for several minutes twice a week.

See if the tree responds by putting on new leaves over the course of two weeks. If desert trees are not getting enough water they respond by drop their leaves, resulting in a thinning of the canopy.

If this tree continues to be underwatered, limbs may die back. It is important to water this tree with a lot of water at one time and then not water it for several days.

Q: Do “wild” mesquite trees have extensive and invasive roots? My neighbor has native mesquite trees on his property and they grow fast without any applied water but they are close to my property. I have a lawn and a septic tank that I am concerned about.

A: The roots of mesquite trees can be extremely invasive. If they are growing in a dry area and their roots find water, they will invade this supply of water.

Septic tanks are ideal growing environments because they contain water, nutrients and an air supply. Mesquite roots can tap into water supplies as deep as 200 feet if given the chance and other sources of water are not available.

Mesquite roots also can grow in shallow soils without deep roots. If roots are close to a lawn and no other water is available, then most of the roots will invade the lawn. If roots find water on the other side of a wall, then roots will grow into that area and easily lift a wall and damage or destroy it over the course of a few years.

Mesquite trees are opportunists when it comes to water. Observing a native mesquite tree will tell you if it is found water. When they find water their growth is luxurious even if there has been no rain for months.

But they cannot grow rapidly without water. It is impossible.

Q: I have two separate containers of bamboo growing in water. Each has three stems. I water them with bottled water. Three days ago I added water and the next morning yellow leaves developed.

I completely changed the water and added liquid vitamin B since I didn’t know what else to do. The yellowing stopped. What did I do wrong? How can I save them? Will the leaves ever return to green?

A: The bamboo you are talking about I assume is lucky bamboo, the houseplant. Lucky bamboo is easy to grow in water as long as the water is free of chlorine and fluorine residues and changed frequently.

Even though you are using filtered water it is best to change the water in the container once a week. Wash the inside of the container and any of its contents to remove fungi and bacteria that might be growing in the water.

Filtered water is better to use than tap water but any water should be replaced weekly because of increasing salt content. As water evaporates from the container and the plant uses water, salts in the water become more concentrated.

Filtering does not remove most salts from water, but these nutrients are not enough for plants. When adding filtered or bottled water back to the container add a small pinch of houseplant fertilizer to it as well.

Changing the water did more for the plant than the vitamin B. Will the yellow leaves ever return to green? It depends on the problem and how badly the yellow leaves have been damaged. If the yellow leaves are not damaged badly, try spraying the plant with a very light application of a houseplant fertilizer.

Q: I have some very nice looking crookneck squash plants this year. But 80 percent of them are male or at least they only produce male flowers. I know because I go out and pollinate them each morning. What do I need to do to get more female flowers produced?

A: Squash produces both male and female flowers on the same plant. The first flowers produced on squash are usually male, and then female flowers are produced a bit later. So be patient.

Newer hybrid varieties were developed that produce more female flowers earlier in the season and sometimes so early there a not enough male flowers for good pollination. In short, select a hybrid squash plant variety next year that has a history of producing female flowers early in the season. Gardening catalogs should tell you this.

Secondly, be patient and female flowers will come. Hopefully, female flowers will not be produced so late that temperatures are too high to prevent good fruit set. Next year plant as early as weather permits and don’t delay it to later in the season when summer temperatures are high.

Q: Is there any value to a saguaro cactus that has fallen over? It is about 6 feet tall.

A: Opinions vary. Some say you can salvage any arms growing from a saguaro and use them for propagation while others say you cannot. A saguaro arm that is planted may take up to two or three years to successfully root into the soil and produce a new plant.

If it is to be done then it is best to avoid doing it during the winter months.

The arms are trimmed at the joints and allowed to heal for two to three weeks in the shade. Rooting hormone is applied to the end of the arm entering the ground. The soil is amended and watered every two to three weeks during summer months after planting.

If the saguaro does not have arms then the arms cannot be used for propagation.

Saguaro has a shallow root system that does not extend very far from the trunk. If it has blown over and still has some roots attached it may be possible to replant it.

In cases like this, the Saguaro is staked and supported upright from three different directions. Guy wires that have hose surrounding their outside to prevent plant damage are looped around the trunk of the Saguaro to keep it from moving.

Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.