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Saturday, July 18, 2015

Attention Bay Area Transplants: Plant and Care for Fruit Trees Differently in the Desert

Q. We just moved from the Bay Area in California to Las Vegas and we brought some small trees with us and they are having a rough time. We'd like to know what to do to help them; Granny Smith apple, a 5 variety grafted apple, a 5 variety grafted pear, a calamansi, a Meyer lemon, a Valencia orange and a cherry tree. I'm pretty sure the cherry is dead and the 5 grafted apple has lost all of its foliage and all of the leaves on the Granny Smith are turning brown and drying up. The pear has actually produced new leaves, but most of the leaves have some brown on them. The trees were in pots but we worked hard digging in the clay and we put some gypsum in the bottom of the hole to try to break up the clay. Any recommendations on more things to do?

A. I am sorry for this much delayed answer to your questions. I have been working outside of the country and I reserved your question for a bit later response because it needed to be more detailed. I needed to respond to you about the time of year for planting, preparation of native desert soil at the time of planting, irrigation and the use of mulch here.

Bare root fruit trees arriving in Las Vegas from Dave Wilson Nursery. Best time to plant fruit trees is late winter and very early spring.
Fruit trees are always going to struggle if they are planted during the summer months or just before the summer months. Summer is absolutely the worst time to plant fruit trees in our desert climate. It may work in San Francisco but I avoid summer planting like the plague. The optimum times are mid to late winter, early spring and the fall months of September and October.
Our desert soils here are horrendous so you must use soil amendments at the time of planting. I use straight compost and mix this 50-50 with the native soil that I removed from the planting hole. I dig the hole very wide but only deep enough to accommodate the roots of the tree or root ball from the container. I dig a hole that is about 3 feet in diameter or about three times the diameter of the roots.

The surface of our desert soil here in Las Vegas
At the time of planting I make sure that the hole and the contents of the hole is sopping wet. Never put dry soil or dry amendments in direct contact with plant roots or plants will suffer a setback. If the plants have been in containers, I "fluff out" the roots from the edges of the root ball at the time of planting. If there are large roots present at this edge, I cut them off.

Once planted in this slurry of soil and water, I make sure the tree is staked so that the roots no longer move during strong winds. One of the least expensive ways of staking the trees is to use a 3 foot length of 3/8 inch rebar pounded through the backfilled hole and into solid ground beneath the hole immediately next to the plant. I use green nursery tape, which is soft and flexible, to tie the trunk of the tree tightly to the rebar. This rebar is removed after one complete growing season.
Rebar driven into the planting hole next to a newly planted tree BUT IT WAS NEVER REMOVED!!! C'mon, it has to be removed at the end of the growing season or this kind of damage is done. Use a hammer, whack it a few times and pull it out. It is not that difficult.
I apply surface mulch around the tree a distance of at least 6 feet in diameter and 4 inches deep. Wood mulch, not bark mulch, greatly improves the growth of the trees during the first couple of years. Keep this surface mulch away from the trunk of young trees a distance of at least 6 inches to a foot until they have been growing about four or five years.
I have put this picture of mine in this blog several times to demonstrate the value of applying wood surface mulch to early fruit tree development. If you want good fruit tree development in the desert, USE surface mulch!!!
Proper irrigation is critical. It is best if the trees are planted so there is a basin about 4 inches tall and surrounding the tree that can be filled with water from a hose. After watering with the hose three or four times you can switch to drip irrigation or any other form but the first few irrigations should be done with the hose to settle the soil around the roots. 
Irrigation basin surrounding fruit tree
Drip irrigation for new trees should have at least two drip emitters located about a foot away from the trunk. In later years, two more emitters can be added to the trees as they become larger and move the emitters to a distance of about 18 inches from the trunk. As trees become larger they will require more water. It is easier to add more emitters than it is to add more minutes to that station which forces all of the plants on that station to receive more water and will most likely result in water wasted.

In midsummer, if you have mulch on the surface of the soil, water deeply twice a week to a depth of 2 feet. It is impossible to tell you how much water this is in minutes. Generally speaking, a 5 gallon tree will require 5 gallons of water at each irrigation. One, 5 gallon per hour emitter running for one hour is enough water. But, if the water needs to be distributed over a larger area than use two, 3 gallon per hour emitters and run it for 50 minutes. If you must use four emitters for better water distribution, use 2 gallon per hour emitters and run it for 40 minutes. A 10 gallon tree requires 10 gallons of water each irrigation. You would use the same logic for sizing the emitters.

Full-sized fruit trees like peach may require as much as 30 gallons at each watering. Six, 5 gallon per hour emitters that are run for one hour would give the tree enough water. But on larger trees I like to use bubbler and basin irrigation.

 Be careful not to irrigate too frequently. When you do irrigate, irrigate more deeply but less often. You should never have to irrigate every day if you are irrigating correctly.

Fertilize the fruit trees once a year in January. You can fertilize more than this but it's not necessary.
Here a 5 gallon bucket of compost is applied to the irrigation basin of fruit trees during late winter
The fruit trees you mention, citrus will be tender here during the winter months when temperatures dropped to the low 20s or even the teens at times. The most tender of your citrus are the calamansi and the orange. They should be planted in areas where there is a lot of reflected heat from walls and away from strong winds. The other fruit trees should withstand our winter weather with no problems.

Fruit trees should have no problem in full sun. Those trees that are planted close to very hot walls or in areas of reflected heat may have leaf scorch. Applying 3 to 4 inches of surface mulch to the soil beneath them will help a lot.

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