Page 8

8  May 31 - June 6, 2012

DesertStarWeekly.com

garden guru

Citrus for the Desert

By Chris Hermann

For desert gardens, citrus trees offer a large variety of benefits including evergreen foliage, fragrant flowers in season and decorative, tasty fruit. Generally, the sweet varieties of fruit will form sugars best in moderate to high heat. Sour types do not need as much heat.

Standard of Dwarf

We are often asked “what is the difference between a dwarf citrus and a standard citrus?” The answer is that almost all citrus sold commercially have been budded or grafted on an under stock. An under stock is the root plant onto which a shoot has been grafted to produce a new plant. For dwarf and semi-dwarf citrus, there are two types of under stocks: trifoliate orange or ‘Flying Dragon’. The trifoliate orange under stocks produce trees 8-10 feet tall with some reaching 15-20 feet. ‘Flying Dragon’ produces even smaller trees of 5-7 feet all at 13 years. Grafted trees begin bearing fruit in just a few years, whereas seedling trees will take 10-15 years. Standard size citrus trees will mature at 20-30 feet tall and wide and are grown on a variety of under stocks.

Planting New Trees

Deep, well-drained soil is a must for citrus. In frost-free areas, they can be planted anytime. It is a good idea to plant in the spring after the danger of frost has passed in colder parts of the valley. Plant spacing of citrus trees, like other landscape trees, is dependent upon the ultimate growth of the tree. Typical spacing for a standard grapefruit is 20 feet and other citrus is 15 feet. Find the warmest location available – in full sun or with some afternoon shade - and avoid planting in lawns.

Irrigation

Irrigation for citrus is different when it is newly planted versus when it is mature. For newly planted trees, build a four foot diameter basin around each tree with sides about six inches in height. Thoroughly water the root ball and fill the basin and

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soak the soil well at least twice a week from March to May. It is important to note here that all trees in your garden should be on a separate irrigation control valve so that watering can be monitored correctly. Soak citrus three times a week from June through September and water every 10-12 days during the winter months. After trees are established, maintain a dry area about 12 inches in diameter around the trunk. The water needs to move away from the trunk, therefore, soil should be slightly higher around the trunk. Continue to expand the basin so this it is slightly wider than the spread of the branches. Irrigation depth for citrus is best at three to four feet deep, and you should allow the soil to become mostly dry prior to watering again. In well-draining soils, a good rule is to water trees every two to three weeks from October through February, every 10 to 14 days March through May, and once a week June through September. If you have the heavier clay soils of the east valley, you will want to water less often.

Fertilization

The first application of a complete citrus fertilizer should be made in February to help set blossoms. One application per month should be made through September. At a minimum fertilize on these holidays: Easter, Memorial Day and Labor Day. If trees are in lawn areas, it may be helpful to add a bit more to compensate for the leeching that will occur with the over watering. Spread fertilizer evenly across the watering basin and water thoroughly after applying.

Pruning

Dead wood, crossed limbs and haphazard growth should be removed. Pull off suckers that grow below the bud union. Lowhanging branches around the perimeter of the tree should not be removed. They help the tree shade itself and prevents sunburn of the bark. If the trunk is exposed due to pruning, whitewash the trunk or wrap it for protection.

Pests and Disease Control

The most common citrus pests are aphids. Spray for them just prior to or at the first flush of new growth – late February to early March. A second application may be necessary two to three weeks later. Thrip insects generally arrive with hot weather and can be controlled with insecticides.

The Best Choices in Citrus Oranges Valencia and Cara Cara Mandarin Dancy and Gold Nugget Murcott Grapefruit Rio Red Lemon Eureka Lisbon Lime Bearss Seedless Mexican Improved Meyer Tangelo (a cross between mandarin and grapefruit) Minneola Kumquat Nagami A bacterial blight, spread by the Asian citrus psyllid, recently appeared on a lemongrapefruit hybrid tree in Hacienda Heights, California. The disease attacks a tree’s vascular system, causing misshapen, bitter fruit before killing the tree. It is carried by the Asian citrus psyllid, a gnat-size flying pest that first appeared on domestic fruit trees in California in 2008. Citrus trees are sprayed by commercial growers before being imported into the valley. The Riverside Agricultural Commissioner requires certification that all citrus trees being sold here are certified that they have been sprayed. To date, there is no cure for the disease, only prevention of its spread. See you next week! Chris Hermann, RLA/ASLA chris@aunteffiesgardens.com

Desert Star May 31, 2012  

Desert Star May 31, 2012

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