Desert plants reduce need for water but produce no shade
QI’m transitioning to a landscape with only Mojave Desert native plants. Cactuses, yuccas and agaves were planted early last spring and are doing well. Will this type of landscaping ever be free from irrigations like they are in the open desert?
A: That’s a tricky question because it assumes you’d be happy with this type of natural landscape. There is not much shade in the open desert. If you prefer larger plants to create shade in your landscape, then having additional plants might be worth the extra water.
If you like the open desert and retreating into your house for shade then, yes, you can probably achieve a landscape without extra water. It might not be very pretty, but you can do it. If not, then it will take extra water to get what you want.
Water use in landscapes is driven by the number of plants growing there, their mature size and if they are desert-adapted or not. Water use increases as the number of plants increases, the mature size of these plants and if they originate from the desert or not. Wise placement of these plants can create very pleasurable outdoor living spaces.
For every plant that survives in the desert, perhaps 1,000 or more die because they don’t get enough water or are not established in the best location for their survival. Homeowners expect every plant in their landscape to survive.
Plants make the air cooler. They transpire water from their leaves. This water loss from the leaves cools the air. And don’t forget the comfortable shade they produce as well.
Water and comfort are trade-offs. To get the cooling shade from a tree requires extra water. If you want trees to shade your home during the summer months, then this requires water.
Do you want a garden? Butterflies? Hummingbirds? These add to our quality of life. This is not a frequent occurrence without occasional extra water to support this kind of habitat.
Good looking plants require water unless you like the look of our native plants growing with the limited supply of water. Trees like mesquite and acacia can look a little sad growing in the open desert. But in a wash with a perennial water supply from rain runoff, they can be full and beautiful to look at.
So, I doubt if you can have a good-looking, even sparse, landscape without some additional water. But you can certainly reduce the amount of water needed in your landscape by carefully selecting the plants you grow in your landscape and supply applications of water
judiciously and at the right times.
Q: I see landscapers putting new plants in the ground without removing the black plastic pots. I see these same plants thriving and doing a whole lot better than some of my own that I have planted in amended soil and surrounded with mulch. That really ticks me off.
A: Sometimes it doesn’t seem fair. You do everything right, and your hard work doesn’t seem to pay off. At least in the short run. Plants will grow in water if it has air bubbling through it and fertilizer available. That doesn’t mean it’s a healthy environment for their long-term survival.
Soils used to produce plants in containers are inexpensive to make, lightweight so they are easy to carry and transport and drain water quickly. Plants growing in containers must be watered often and fed with regular applications of fertilizer. Container root environments encourage fast plant growth but are not intended for the long haul.
Plants in containers will continue to do well after planting in the ground, container and all. This is because the containers, together with the plant roots, are surrounded by cool soil and no longer punished by intense sunlight and high temperatures.
After planting, plant roots grow through the bottom of the container and into the surrounding soil in just a couple months. The top of the plant grows quickly but its roots are surrounded by the plastic container, impeding its establishment.
Vigorous plants survive through this ordeal, but more delicate ones will struggle and probably not survive. Landscapers are long gone by the time plants begin struggling. Some plants become weak and struggle after a couple of years growing with this plastic container surrounding its roots.
Plants always perform better over the long term if planted into the soil and cared for properly. Some may struggle for the first few years, but most plants perform best if our soil is amended at the time of planting, giving them a good start. Stake larger plants the first year and water so that at least half the roots under the canopy are getting water as they continue to grow.
Apply enough water so it infiltrates into the soil 1 foot deep for small plants and 2 feet deep for small and medium-sized trees. Wood chips on the surface of the soil improve it so that the majority of its feeder roots are growing in the top few inches, which they love but takes a season or two before they catch.
Q: I am growing a new cactus from pads cut from the mother plant. You recommended I amend my soil with either compost or manure before planting the pads. I used a local planting soil which was cheap but not a good decision I discovered. Can I amend this soil and fix it?
A: You probably can. However, the soil should not be fluffy but firm after it’s been watered. If it’s fluffy, the cactus will fall over when it gets taller. It will also fall over, or possibly die, if watered too often, watered frequently with small amounts of water or if the water is applied only around its base.
Use native desert soil whenever possible, mix in a small amount of manure and build a 3-foot basin around the plant for containing enough water applied to it. Water it every three or four weeks in the summer, filling the basin to its brim.
Make sure all cuts have healed before planting the pad or it can become infected and rotten. To be done on the safe side, apply a copper fungicide like Bordeaux to the bottom fourth of the pad before planting. This helps keep wounds from rotting when it first gets started.
Plant the entire pad so its flat surfaces are facing east and west and one-third of it extends below the soil. Water the entire basin and let it soak into the soil 12 inches deep. The roots will form from the pad using stored water taken from them.
Q: I have a cactus garden that faces west. Every summer I hang sheets on a clothesline so the cactuses don’t burn from the direct westerly sun and heat. The sheets get stuck in the cactus when the wind blows and pull the small ones out of the ground. If I don’t protect the cactuses this year, will they die?
A: It depends on the cactus and where it comes from. Many people don’t realize that not all cactuses require the same type of environment. They are as individualistic as we are.
Cactuses are found in a variety of climates, from our harsh desert Southwest conditions to shade-loving cactuses to drought-tolerant cactuses that survive on moisture from ocean fogs. For this reason, some cactuses may thrive in your western exposure while others need protection.
You should know by now which cactuses are struggling and which are not. Yellowing or turning white on the west sides of these cactuses is sunburn. Move them to new locations with filtered light or eastern exposure. They will recover. Leave the ones which seem to handle the intense sunlight alone.
Learn their common and scientific names and where they come from. Sometimes the presence of a covering of dense spines or “fur” can provide a clue about their sensitivity to direct sunlight and their need for protection.
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.