How to water desert trees

Plants

Desert trees anchor a xeriscape. Such important plants need proper care to look natural and avoid damage. Amazingly one of the best things you can do for a desert tree is NOT water it all the time. Over watering encourages fast, weak growth. When summer windstorms come, a spindly tree loses main branches, potentially ruining its form. My neighbor had an entire tree disappear in a windstorm!

Severely_pruned_mesquite

This Mesquite is nearly full grown, yet has been severely pruned to prevent damage from wind. Watering less frequently would give a better natural form without the need for pruning.

When I plant a young desert tree, I build a basin with edges about 2 feet away from the tree’s trunk. I’ll start by watering the tree every few days for the first week or two while it recovers from transplant shock, then I fill the basin once a week while the tree gets established, about the first year. After a year, a desert tree can live with watering once every 2 to 4 weeks. If the tree seems to be growing slowly, you can increase the water frequency to no more than once per week.

Baby Palo Verde basin

A lush baby Palo Verde tree with a 2 foot basin.

As the tree grows, expand its basin. Once a year in spring you can rebuild the sides of the basin farther away from the trunk. The basin around the tree allows you to give a large drink with each watering, penetrating farther into the soil and allowing the trees roots to grow deeper. Shallow watering encourages shallow roots, which allows the top of the tree to become heavier than the root strength. In order to allow the basin to fully fill, turn a hose on at a trickle and set a timer for an hour, monitoring to make sure your basin doesn’t overflow. Or if your tree is on your irrigation system, you can add the number and flow rate of emitters needed to fill the basin in the time scheduled for your system.

Desert_tree_basin

A larger basin on a more mature desert tree. This basin measures about six feet across and is doughnut-shaped to encourage roots to spread away from the trunk. This tree blew over a few times while young and needed stronger roots.

Once my desert trees have doubled in size or seem well established, they can be watered even less frequently. A few of my trees border a low spot in my yard where water pools when it rains. These trees are not on my irrigation system and I hardly ever water them by hand. The winter and summer rains give them deep drinks which keep them healthy. They usually keep their leaves all season long, so I know they are getting enough water.

Juvenile_Palo_verde

This Foothills Palo Verde has been in the ground about 5 years and no longer needs any irrigation since it borders a low spot in the yard.

When watered appropriately, desert trees grow slower with more proportional shape and stronger branches. Over time they can still grow to mature heights of up to 30 feet, and much more quickly than they would in the desert.

Summertime landscape chores

Seasons

How did you enjoy the flooding?

basin flood

Phoenix flooding

With all of the rain, my landscape is looking green this summer! I’m especially happy that the young cacti in my yard that were a little sunburned look much healthier. The first year in the ground is always hardest for a plant.

My bushes grow more than average with the extra water, which means they look due for pruning. Since I don’t like gumdrop shapes, what is the best way and timing for pruning?

summer desert bushes

Bushes have grown and greened up with the rain.

I found a pruning schedule with recommendations specific to each plant. For many bushes it recommends only pruning once or twice a year. Here is another pruning overview by U of A. I’m surprised to find that they don’t recommend pruning Texas Sage in summer, since it tends to be one of the most often-pruned plants.

Texas sage

Texas sage in bloom, getting large and shaggy

A late summer pruning helps trim back excessive growth, but will reduce blossoming ends and could be put off until spring. If you prune, try selective thinning, where you remove entire branch sections, either to a fork or to the ground, to open up the bush. It’s harder, scratchier work, but results in a more natural shape.

Some desert trees should be pruned later in the summer (as opposed to spring) to prevent excessive growth. Now is a good time to thin Mesquites, Ironwoods, and Palo Verdes.

So, with that information, there’s probably less pruning to do than you thought. Perhaps just some thinning of a few plants that have grown more than you wanted during our rainy season.

Pruning: gumdrops and lollipops?

Seasons

Yesterday a landscaper knocked on my door and asked if I wanted my bushes pruned. Sorry, but I’m too picky about how they look.

Most landscaping companies prune bushes into little balls and cylinders that don’t look natural at all. They prune palo verdes into single stemmed, tortuously twisted trees that look terrible.

In my opinion, a native landscape should look somewhat native. So what pruning do I do?

Arizona xeriscape wildflower garden

Unpruned wildflower garden

Trees

I prune my trees when young to usually have a single trunk at the base and then branch into multiple trunks within the first 3 feet. Then I prune the branches to raise the canopy to whatever height I need for the space and allow me to see the branching trunks. Once the tree approaches the size I want for the main branches, I may let it grow or just prune the branches that fill in or grow downward. I don’t worry about my desert trees getting top heavy and blowing over in wind storms because I water them deeply and infrequently to encourage root growth. The limited water also limits the canopy growth and keeps the wood dense and strong.

pruned palo verde

pruned palo verde

Bushes

Some bushes don’t need to be trimmed. If they have a nice shape and are in a spot where they can grow to their mature size without crowding, then I let them go. Creosote and jojoba don’t need pruning. I do have texas sage which I prune twice per year in summer and fall. When some of them get large the┬ábranches fall over leaving a gap on top. Native wildflowers like brittlebrush and marigold can get chopped off when they go dormant or leave them for a natural (if brown) look.

If you have a native landscape and your plants are mature, you can adjust the water so they grow slowly never need pruning. Prickly pear are a great example of this: with lots of water they will grow lots of pads, and you may have to cut some off to maintain the shape or size you need. With less water, they will grow fewer pads and stay smaller.

Texas sage needs pruning

Texas sage needs pruning

Cacti

Cactus don’t need pruning. I do cut pads off prickly pear. I will cut out extra canes of ocotillo if I don’t like where they branch. I never prune desert spoon, agaves, or yuccas. (Large pruned agaves look like pineapples.)

The plants that need the most pruning for maintenance are the non-natives: rose bushes, fruit trees, etc. Native landscaping requires much less pruning.

Wild native plants never get pruned

Wild native plants never get pruned

Dormant for the summer–summer break!

Seasons

Most of the United States enjoys the growing season during the summer months. Unlike the rest of the country, plants in Arizona survive the heat by going dormant during the hottest part of summer. This means you can take a break from landscaping and just enjoy the yard. It’s nice to not have to do yard work when the temperature is over 100 degrees.

Watch your plants for signs of stress indicating they aren’t getting enough water. When prickly pear pads start to wrinkle or leaves start to die, your plant may need a drink. Keep in mind that some plants like ocotillo and palo verde lose their leaves as part of dormancy and are not dying.

Ocotillo dormant

Ocotillo losing leaves

Palo verde in June

Palo Verde in June

Desert marigold dormant

dormant desert marigold

After kicking back for the summer, you’ll enjoy getting back to work in the fall.

Woolly butterfly bush

Toughest drought-tolerant plants for your desert garden

Plant selection, Plants

In order to maximize the number of plants in your garden without overloading your drip system, you may end up planting things that you expect to survive on their own. Luckily, there are some un-prissy plants that can do this. These survivors deserve a medal, instead of being overlooked and under-appreciated. After all, this is the desert! When I moved to Arizona, the house I bought had been vacant for two years and some of the plants in the yard were still alive. That is the kind of landscaping I want.

Trees

Natives: Foothills palo verde, Ironwood, Joshua tree

Non-natives: Catclaw acacia, Whitethorn acacia, Elephant tree (frost sensitive), Smoke tree.

Shrubs

Creosote bush, Desert holly, Four wing saltbush, Jojoba, Las Vegas buckwheat, Limber bush, Mormon tea, Pink fairy duster, Shadscale saltbush, Warnock condalia, White bursage, Yerba santa

Woolly butterfly bush

Woolly butterfly bush

Wildflowers, agaves, yuccas, others

Bahia, Desert sunflower, Prickly poppy, Variegated century plant, Bear grass, Banana yucca, Our Lord’s candle yucca, Candelilla, Slipper plant, Bush muhly grass, Medicinal aloe