Q: I put in a lot of effort into planting asparagus. I have a large planted area but no asparagus. I planted Mary Washington this year and many times in the past, but I have had no luck. Are the trees nearby this area competing with them too much?
A: There is a lot to cover regarding asparagus growing here. First, there is no problem planting asparagus among trees if there is room. Asparagus gets 5 feet tall after harvesting the spears, so make sure it has room to grow to that height.
I have had asparagus planted among fruit trees, as well as alone in rows, since 1996. I planted asparagus in 2019, and they are coming up nicely. This is a great climate for asparagus if it’s planted and managed correctly.
I have grown about 15 varieties of asparagus for comparison purposes in our Mojave Desert climate. They have all done well, but there are some differences among the varieties. Stay away from heirloom varieties such as Mary Washington because they don’t produce enough spears in any climate. There is nothing remarkable about them.
Expect an asparagus bed to last about 20-25 years if managed correctly. They do well with drip irrigation. I would use drip tubing with emitters spaced about 12 inches apart or plant them in containers for small spaces. In rows using drip tubing, plant in a triangular pattern so that crowns are 12 to 18 inches apart on either side.
Asparagus plants love rich soil and water, but they also like their roots and crowns to breathe. Mix with desert soil an equal volume of rich compost at the time of planting about 12 inches deep. Buy 2- or 3-year-old, all-male crowns and plant them 8 to 10 inches deep. Make sure the soil in the asparagus bed is free of any rocks or they will produce crooked spears.
The soil must drain water easily in a few hours after irrigation. Irrigate thoroughly after planting but don’t irrigate again until the soil is slightly moist at 6 inches deep.
If you’re not sure about when and how much to irrigate, follow my blog, Xtremehorticulture of the Desert, my YouTube video or podcast on how to irrigate. If watered too often, asparagus roots and crowns will suffocate and rot.
Plant UC 157 developed by the University of California for the hot desert and plant them from mid-January to early February. Stay away from planting by seed unless you are an experienced gardener. If you want some variation in spear colors, mix in a variety called Purple Passion, but keep in mind they don’t produce as many spears as UC 157 but are sweeter to the taste.
Each year, before the start of the growing season just after the Christmas holidays, apply about 1 inch of rich compost on top of the soil above the crowns and water it in. If the soil has plenty of organics in it already, then use a mineral fertilizer such as 16-16-16.
Q: I have two dwarf magnolia trees in my courtyard in front of the house. They started dropping leaves and they’re kind of scarecrow looking. What do I do?
A: Let’s get something out of the way early. This is not magnolia country, so they will require extra care and attention here. I hate to sound like a broken record, but it is either water or soil improvement or both.
Is it planted in rock? That’s a mistake if they are. These are not desert plants, so they will not like rock. The soil around them should be covered with a 4-inch layer of woodchips instead.
How many emitters do they have? They will need at least four if they are 4 or 5 feet tall. These will be placed in a square pattern about 18 inches from the trunk. This will be enough until they get about 10 feet tall, and then you probably will have to bump it up to about six or eight emitters spaced evenly under the tree canopy.
Making sure these trees get more water will stimulate more leaf development and a denser canopy. The water should be on long enough for it to drain to about 18-24 inches deep after each watering. Use a steel rod like a 3-foot-long rebar to judge the depth of irrigation.
Q: We have a 5-year-old apricot tree. Previously, it’s always seemed happy, but this year it leafed out beautifully, then it started dropping its leaves. Apricots are still on the tree but have not developed yet. Then this week, half of the branches on one side are leafless.
A: Pictures were sent to me of this tree, so let me explain what I saw. The apricot tree is 6 to 8 feet tall with a similar spread but leaning strongly toward the light but away from some taller shrubs on one side. Leaves are on the ground and have dropped from the side away from the light. The week it dropped its leaves was a hot week and then it got cool again.
Trees drop their leaves because they are not getting enough water. They also drop leaves if it’s too dark, but I think in this case it’s a water issue. A lack of water can be from not enough water applied to the soil under the tree, borer damage in the trunk or several large limbs, or a disease problem.
I’m going to rule out the disease possibility because it is highly unlikely in the desert. Borer damage is a possibility except the leaves are dropping at the wrong time of the year and from half the tree instead of a branch. Borers cause leaf drop during the heat of the summer, June or July, frequently affecting an isolated branch or two. So, let’s rule out borer damage.
It is possible this tree had gotten larger and was not getting enough water. With a shortage of water, the distribution was not over a large enough area under the canopy to satisfy its roots. As trees get larger, they require more water distributed to a larger area under the canopy.
To test this idea, use an inexpensive sprinkler on the end of a hose, connected to a mechanical timer at the hose bib or faucet. Put the sprinkler about 2 feet from the trunk of the tree and turn on the mechanical timer for two hours so it wets the soil deeply in an area about 5 feet in diameter. Do the same thing to the other side of the tree. Do this twice a week for the next two weeks and let’s see if the tree responds.
If I’m right, you will see new growth coming from the limbs that are bare, and where there are leaves, you will see new growth. If this is the case, increase the number and size of the emitters. Place one drip emitter scattered about every 2 feet under the canopy of the tree. The water should penetrate the soil about 18 inches deep after an irrigation.
Q: We had three African sumac trees planted in our backyard 1½ years ago. We treated them the same during this time, but the tree the farthest away has large dark green, healthy leaves and the other two trees have lighter color leaves and they are curled.
A: The problem is obvious in the third picture you sent of the close-up of tree leaves. The curled leaves you mention is obvious damage from weed killers. A better description of the leaves is not to label them curled but the leaves appear stretched. The veins in the leaves are more parallel with each other and the leaf color is yellowish rather than green.
Most likely a neighbor was using this weed killer on a hot, windy day. The fumes from this weed killer volatilized into the air and was moved with the wind. Frequently these types of weed killers are applied to lawns to kill weeds in late spring or early summer. Some plants are more susceptible to these fumes than others. This is a good reason not to use weed killers any day that it causes leaf movement in trees.
What to do? Make sure young trees like these are receiving enough water. Trees of this age and size should have four drip emitters applying water 12 to 18 inches from the trunk about twice a week. More frequently when it gets hotter. When water is applied, it should move through the soil to a depth of about 18 inches.
To encourage growth and recovery, apply a lawn type fertilizer high in nitrogen, the first number on the bag. Use fertilizer stakes inserted into wet soil near the drip emitters or push a shovel into the soil large enough for a couple handfuls of fertilizer. Fertilizer and water will encourage the growth of leaves with a darker green color and increase the density of the trees.
You will see the trees improve in appearance and growth with the applications of high-nitrogen fertilizers and water.
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.