Drought Can Substitute for Winter Cold in Asparagus

Q. I am trying to figure out when asparagus goes dormant in the desert. I have been doing some research, but I can’t find information about how to handle the dormancy period in the desert. Any ideas?

This is what you hope will happen in the winter to asparagus. In warmer climates it stays green. Turn off the water to force the plant to go dormant.

A. The usual information about asparagus says it turns brown, or goes dormant, as weather gets cold. That’s true in Michigan or Washington state. Sometimes asparagus grown in warm deserts doesn’t turn brown. It might stay green all winter long.

            Wait for the coldest part of the winter, cut it down like it was brown and turn off the irrigation. In about a month, irrigate and fertilize again to push a new crop of spears. For some plants, drought can sometimes substitute for the dormancy of winter cold.

            Not irrigating can “trick” the plant into “thinking” it just got through its dormant period. In the tropics, we let asparagus “dry out” for a month during the dry season and then start up the irrigation again. Cut it back during the coldest month, turn off the water until the soil dries, put manure, compost or fertilizer on top of the soil and then start watering again. 

When to Harvest Pistachios

Q. When should I harvest pistachio nuts from my five-year-old tree? In October the nuts were yellowish green with a red blush covering them.

The red blush on the nuts means they are close. Harvest after the "meat" has filled the kernel and start to split open.

A. The red blush is an indicator that your harvest season has arrived or perhaps even late. It’s better to look at the number of split nuts on the tree. The general time for harvesting may start as  late as late August or early September and extend through the middle or even end of October.

The nut will start to split when its ready to harvest. Turning red may be a bit late.

            The time to harvest is when the nut inside the husk fills the shell and can be removed. Commercial growers look at the number of split nuts on the tree and whether it might rain or not. Rain will mold pistachio nuts if they are split open. Pistachios are grown in arid or desert parts of the world where, like dates, rain is considered a foe. When harvest time is near nothing beats taking a few nuts off the tree and see if the “meat” is plump and separates easily from the shell.

In some parts of the world there is enough rainfall to grow "wild" pistachios which means they are grown, usually on government land, without supplemental irrigation.

            Drying the nuts off the tree enhances flavor, causes more of the nuts to open and the “meat” to separate further from the shell. If rain is predicted soon, harvest them before they mold on the tree.

Asparagus Growing is Easy with Compost or Manure and Water

Q. My asparagus attempt resulted in five out of 10 crowns dying.  I did as you suggested and dug down as deep as my tiller would dig about 13".  For better drainage I drilled holes another 12" deeper and filled them with gravel. I ordered Jersey Knight asparagus and planted as per their instructions as well.

'Purple Passion' asparagus has purple stems which turn green when cooked. To get long straight spears requires plenty of nutrients, water and cool temps starting to warm up.

Asparagus planting done in late fall or very early spring with amended soil with compost or aged manure. Drip irrigation can be used but watering should follow a similar pattern to watering fruit trees.

A. The usual reason for asparagus dying or growing poorly after planting is because the plants are watered too often, and the crown or roots drown. Asparagus must be planted in soils that don’t hold water. If the soil holds water easily or there is poor drainage then consider planting asparagus crowns just below the surface of the soil and mound the soil eight or 10 inches above it. Mounding the soil provides better drainage in heavier soil.

Asparagus crowns like this one can give you 100% male plants which produce higher yields. Taste is the same.

            Don’t water deep rooted asparagus the same as other annual vegetables. They could be watered with other perennial vegetables such as artichokes or even fruit trees or landscape trees and shrubs! If in doubt, use a soil moisture meter with the tip inserted at about 4 to 6 inches deep in the soil. Never trust a dry soil surface to tell you if the soil where the roots are growing is dry or wet. Water again when the average needle measurements register midway or around “5” on the moisture gauge.

Asparagus can be started from seed but its better if grown from crowns. Seed results in a 50/50 stand of male and female plants. Female plants are not the heavy producers that male plants can be.

            Asparagus grows in the wild near the edges of irrigation ditches in the desert. But not in the ditch. This means they like to get their “toes” occasionally wet but not submerged. These locations are similar where palm and fig trees like to grow. I had good luck growing asparagus between fruit trees when they were young and there is enough light. When fruit trees get older and dense, it is more difficult to grow asparagus because there is less light. Move the crowns to new locations during the winter months where there is moisture and adequate light.

If the winter is not cold enough to kill asparagus tops then cut them back, turn off the water for a month and resume production.

            Adding rock beneath the crowns doesn’t help drainage at all. It’s the same story with sand. To get any kind of soil improvement requires additions of 80 to 90% sand above and below where the plant roots are growing. Research has not looked at gravel but I assume it is the same. But additions of rock above the crowns cause them grow crooked spears. Straight spears require soil above the crowns without rocks.

            In my trials over the years, all varieties of asparagus (12 different varieties) produced spears but the longest and most saleable spears were produced by UC151 hybrids bred by the University of California in Riverside for the hot, dry desert. All the “Jersey” varieties, bred by Rutgers University (New Jersey), didn’t yield as well in the Mojave Desert. You get quality spears with other varieties, but the spears must be harvested earlier than UC151 and this makes them shorter. This holds true for old-fashioned varieties like Martha Washington and most purple types.

            I fertilize asparagus in midwinter with a layer of manure or compost applied once a year and watered in. You can also use a high nitrogen fertilizer, but it will not improve the soil like manure or compost does.

Ideal Time to Plant Anything in the Desert

Q. Is it too late to plant new plants?

Yes, thats my shoe on a soil we will soon plant to vegetables. But not without adding compost at a rate of about 1/3 to 1/2 by volume to that soil.

A. October and most of November are good times to plant in the Eastern Mojave Desert. The ideal time for planting is in the fall and spring. No one argues that but plants are for sale 12 months of the year. Early fall is when I encourage people to plant. Late fall and winter is not the “ideal time” for planting but you can still plant. When planting, always avoid the intensely hot summer months of the desert.

Always Better in the Ground

It is always better to plant in the ground rather than wait for a better time. Just make sure the planting area is suitable for the plant. Plants do not establish their roots in soil as quickly when the soil is cold. One growing season is all that is necessary when staking most new plants.

Know Your Plants Ancestry

If it’s genealogy is the Mediterranean region or arid parts of the world, it most likely performs best with wood chips covering the soil surface rather than rock. Plants originating from the desert Southwest tolerate rock and poor soils better but don’t necessarily grow to their full potential in that type of soil.

Should I use Rock?

Plants that perform best surrounded with rock mulch covering the soil surface are plants that originate from the deserts of the Southwest. If the soil is poor to begin with, covering it with rock will not improve it. 

Be Sure the Soil Drains

All plants perform better with additions of organics like compost mixed into the soil surrounding the roots when its lacking. Some, like cacti and succulents, require less but they all of them grow better with amended soil provided there is good drainage. All plants that originate from deserts prefer soils that drain water. Plants that originate from wetter places, but can handle the heat, are usually more tolerant of wetter soils.

Fungicides Protect Plants, Just Like Insurance

            Do you have insurance? Companies selling insurance are betting you will not have a problem. You, on the other hand, are betting you might. Fungicide use follows the same reasoning. Fungicides, unlike most insecticides and weed killers (herbicides) protect the new growth of plants and keep diseases from starting or spreading. Because the disease doesn’t occur, you may not be convinced it did any good.

            We collectively use the term “fungicide” to describe any pesticide aimed at preventing a disease from fungi, bacteria, virus or mycoplasma like organisms (MPO). Most diseases are caused by fungi but there are a few, like fire blight, which are caused by bacteria and others like Ash yellows or Ash decline caused by MPO’s.

            Desert climates like ours have a low humidity so plant diseases aren’t frequently seen unless we do a poor job choosing plants for the wrong landscape spots, planting, watering, or managing them. Agriculturally Las Vegas is isolated and that also works in our favor. We have far fewer fruit and vegetable diseases here than in agricultural hotspots.

            What can you do to prevent plant diseases? Clean and disinfect tools and equipment. Whether you are doing it or someone else, make sure these tools are clean and sanitized. Make sure supplies you are using are clean. Clean any used pots and containers with bleach and let them air dry for 24 hours before reusing them. Don’t compost diseased plant parts or reuse them. Instead, securely wrap them in plastic and put them in the garbage. If the disease is known to be virulent such as fireblight, get diseased plant parts off the property as soon as possible. Thin out dense plants to improve air movement through their canopies. Whether you are growing tomatoes, fruit trees or shrubs, when they are dense they need to be thinned by selective pruning and growing vigorously to prevent diseases.

Some diseases (biotic, coming from pathogens) I have found in the desert include:

Fireblight – Asian pears, European peers and apples and including many ornamental plants in the rose family including Pyracantha

Fireblight on Asian pear

Root rot and collar rot – many different fruit trees and ornamental trees and vegetables

Chokes the tree or plant at or beneath the soil because the soil is cold or too wet, poor drainage or all three

Ash decline – most ash trees

Limbs dying in established ash trees

Other suspected plant diseases probably encountered are: oleander leaf scorch, Pierces disease on grape, Verticillium wilt on vegetables and, Fusarium wilt on palms and vegetables, white rot on onion and garlic, summer patch on tall fescue, to name a few.

Always use sanitized equipment and sterile soil and containers when possible. By the way, my favorite sanitizer is alcohol after everything has been cleaned with soap and water.

Where to Get Sabadilla for Insect Control

 Q. I have been looking for replacement of my sabadilla dust that is just running out now. I have been unable to find it.

Pyrethrum (Chyrsanthemum) grown on a farm in Kenya and sold to a European company who makes natural pesticides (pyrethrum powder).

A. I did an extensive search for sabadilla as an insecticide. It is now sold mostly as a homeopathic treatment for sinus congestion. As you know it has been around for decades. I remember it as an "organic" pest control measure before the organic movement began. It is made from the seeds of the sabadilla plant (Schoenocaulon officinale). Others in that old group of plants that served as sources of insecticides include rotenone (aka, derris, from seeds and stems of several legumes) and pyrethrum (extracted from chysanthemum flowers). 

Pyrethrum is now being synthesized industrially (called pyrethroids) and has morphed into manufactured insecticides like permethrin, resmethrin, and others. Pyrethrin morphs are used mostly by the interior pest control industry to control termites, ants and mosquitoes. Some claim the morphs were over profits and others claim it was for effectiveness and the targeting of specific insect pests.

Sabadilla is now sold mostly as a homeopathic medicine for allergy symptoms. 

It has come full circle and is sold for outside pest control use only by one supplier (to my knowledge) and the formulation has changed over the years from a dust (D) to the more popular wettable powder formulation (WP). https://www.mgk.com/product/veratran-d/

Nopal Cactus (Copena varieties from the Sonoran Desert) Grown for Food Elsewhere

Q. I am a special education teacher and gardener in Sonoma County, California, and I've been searching for Copena V1 or F1 cacti to cultivate here in Santa Rosa. I have been doing some research and learned from Everardo Zamora at USON that you had acquired some specimens of this variety some years ago. I would like to pick your brain about their cultivation and potential as an easy-to-grow food source in my area.

Copena flower and fruit production in the Mojave Desert at UNR Research and Demonstration Orchard in North Las Vegas

Bob Morris (Xtremehorticulture) and Everardo Zamora (USON) talking about Copena nopal cacti growth and production in the Mojave Desert

A. 

Bird damage to copena nopal cacti fruit (tuna).

Flower from Copena nopal cactus.

Winter freeze damage to Copena nopal cacti.

Cochineal scale damage to Copena cacti pads

A. Nice to hear of your interest in the Copena nopal cactus. I consider Everardo a good friend. Copena cacti are very easy to grow but it's just too cold during the winter in Las Vegas.  They will have freeze damage a little bit below freezing temperatures (maybe about 30F). Regardless, they produced high quality fruit and pads to use as fresh vegetables, fruit and for livestock feed even after a freeze event. Freeze damage was our biggest problem in the eastern Mojave Desert. These are high quality eating cacti (nopalitos and tuna) from the Sonoran desert and developed by the University of Mexico.

The biggest problems I experienced with them are:

• Cold (freezing) damage from winters colder than the Sonoran Desert
• Bird damage because they are so sweet (may require netting)
• Rabbit damage during the winter because they are spineless and not much out there for rabbits to eat in the winter (may require rabbit protection)
• Constant spraying with streams of water to keep the cochineal scale at bay (no commercial insecticides were applied)
• Controlling leaf-footed plant bugs (a growing problem in the Mojave Desert)

I irrigated them about every 3 weeks with a bubbler in basin type of irrigation to push new growth for harvesting and fertilized them for production once a year in the spring. Plants were established by pads donated from USON. They start flowering in their second or third year after planting.

Narcissus for the Mojave Desert

Q. I accidentally cultivated up a bunch of daffodil bulbs. When is the best time to replant them in Las Vegas? They show no signs of green.

A. If these daffodils have been in the ground in your landscape for several years then chances are you can just replant them and they will continue to flower next spring and probably every year thereafter. If they did not flower last year, or they flowered erratically (some years you got beautiful displays and others were disappointing), then you should read the rest of this information. 

To get consistent flowering year after year, you may need to put them in the refrigerator through the rest of the winter to get consistent flowering. You can also opt to buy "prechilled bulbs". But be forewarned: this refrigerator treatment may need to be done each year to get reliable blooming. This is also true of tulips and some other very popular cold climate bulbs. 

Replant them on the east side of the house so that they get morning sun but are protected from late afternoon heat. Amend the soil with about 20 to 30% compost when planting. Never cover them with rock. Woodchips are okay but not rock. They will not grow well in total shade or in hot bright locations. They will also not grow well in rock.

It takes the right variety of daffodil for it to bloom every year here. Local nurseries rely on their suppliers to sell them the right daffodils for this climate. Las Vegas, climate-wise, is halfway between a tropical climate (think Hawaii) and a cold climate (think Minnesota). Las Vegas lies in the northern belt of climates termed loosely “semitropical”: Cold winters to the north and warm winters to the south.  It lies in the transition zone between the two. Did you see flowers from them before? If you did, then just replant them.

There is never any advertising on my blog. It runs off of donations so here is stuff I found helpful.

Here is another article about this topic.

Here is a source for daffodils that will do well in warm climates. Just enter your zip code.

A second source of bulbs for warm climates.

A third source of bulbs for warm climates.