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FOUNDATION FOR SUCCESS

Climate Know your climate and the peculiarities associated with your locale. In Arizona there are four main growing areas related to fruit production (Figure 1). The main differences in these four regions are related to elevation, winter temperatures and length of growing season. Regions 1 and 2 are considered as low desert and are characterized by warm winter and a long hot growing season. Regions 3 and 4 are considered high desert and mountain plateau regions respectively. They are characterized by cold winters with medium, (150-200 days) to short, (150-190 days) growing seasons.

Fruit and nut trees have what is called a chilling requirement. This requirement varies between varieties within a kind of fruit. The chilling requirement for a variety is defined as the accumulation of hours below 45ºF and above 32ºF. Satisfying the chilling requirement will result in normal growth and bloom following a dormant or winter period. During extremely mild winters the chilling requirement may not be satisfied and will result in uneven bloom. The tree will remain dormant until early summer when a small shoot or several fruit will form on the end of a long naked branch. Varieties which have a chilling requirement of 600 hours or below are termed "low chill" varieties. Low chill varieties should be planted in regions 1 and 2. Normal chill varieties should be planted in regions 3 and 4. Table 2 lists the chilling requirements of fruit and nuts grown in Arizona. In general, the higher the chilling requirement of a variety, the later bloom will occur in the spring. Generally, subtropical fruit are adaptable to regions 1 and 2 while temperate or deciduous fruit are adaptable to all 4 regions. Low chill varieties allow for adaptability in regions 1 and 2.

Figure 1. Arizona Plant Climate Regions

Arizona has very high solar radiation which can result in high temperature stress to fruit trees. Common problems related to this phenomenon are southwest injury, trunk, limb, and fruit sunburn. Even though trees grow best in full sun, precautions to prevent these maladies should be utilized. Partial shade is not necessarily a detriment considering Arizona's climate.

Site and soil Although homeowners are somewhat limited in their choice of a site, it is important to choose as good a site as possible. Avoid low lying areas where cold air will accumulate to avoid spring freezes. Plant trees where they will have good sunlight exposure. To obtain maximum growth and yield a tree must be planted in good soil. This is the number one requirement once the correct variety has been selected. A good soil should supersede other considerations such as sunlight exposure or proximity to house. Without a good root environment the tree will not respond to care in an optimal way.

The main factor in selecting a soil is its ability to drain water throughout the root system area. This is known as the internal drainage factor. We want to select well drained soils or create a well drained soil for fruit trees. To determine the internal drainage factor of a soil, dig an 8-inch hole 32 inches deep and fill it with 5 gallons of water. Let the soil absorb the water for an hour then fill again. If the hole is empty in 24 hours, the soil has good internal drainage. If it requires 48 hours to drain, the internal drainage is poor but adequate. If any water remains after 48 hours do not plant trees. Create a special raised bed or plant in a container if a tree is to be planted in the selected site. In Arizona it is not uncommon to confront a soil condition known as caliche. Caliche is a chalky type soil, white in color and chemically composed of calcium carbonate. It can be found in many forms throughout the soil such as solid layers or crumbled pieces. The solid layers will restrict drainage and need to be cracked or drilled to allow water drainage. Another problem with caliche is its high pH which restricts the uptake of micronutrients such as iron and zinc. Be prepared to add these nutrients if trees are planted in caliche based soil. Avoid poorly drained soils at all cost, they invite failure.

BUYING NURSERY STOCK

An important aspect of the success of home fruit production is the nursery stock. Purchase trees from a reliable, reputable nursery. Reputable nurseries guarantee that fruit trees are true to name, free from insects and diseases and if mail order, are packed and shipped correctly. The cost of trees will be your smallest expense in the long run. Beware of bargains. High prices do not necessarily mean high quality, but good nursery stock is not cheap.

One year old trees are the preferred age for transplanting. Older, larger trees have to be pruned back severely when planted and cost more. Younger trees adapt to transplanting better and develop into healthier, vigorous trees than do old oversized stock. Select trees that are 4-5 feet tall with a trunk diameter of 1/2" to 3/4", with 5/8" being ideal. Trees are characterized as whips (no branching) or in some cases will be branched. Both are good for transplanting.

Local nurseries usually provide trees of proven varieties and rootstocks. Also you can select the tree of your choice. In addition local nurseries should replace unhealthy trees if problems occur.