Site Considerations

Knowing what is ideal among site considerations allows us to know what is less than ideal – building our awareness of risk and where problems will likely occur, includes knowledge of…

Climate

The major climatic influences on any one site vary considerably and are determined by: elevation, marine or fog influence, wind pattern, rainfall amounts by month, slope or exposure, frost free days, average temperatures, and temperature extremes.

In general, citrus requires a great deal of summer heat and relatively frost free sites so it is usually grown on slopes just above valley floors in the southern part of the state. Apricots were historically grown in the Winters area of northern California because of the moderate climate that was influenced by cool breezes from the San Francisco Bay area. More recently the Fresno area is producing early apricot varieties. All of the berries: strawberry, raspberry, blueberry, and blackberry perform better under cool coastal climates.

If you live in an area with strong winds, plant trees in protected locations rather than on hilltops. In areas with spring frost, plant where air flow is adequate, such as midway down a gentle slope.

University of California scientists divide the state into six main agricultural districts for production of temperate fruit and nut crops. The six regions and their important climatic characteristics with respect to growth of temperate tree fruit and nut corps are described in [PDF] California Climate Zones for Growing Temperate Tree Fruits and Nuts.

To learn about your climate consult with your local UC Cooperative Extension Master Gardener Program. California gardeners and nurseries usually refer to the Sunset Climate Zones rather than USDA hardiness zones. The Sunset Western Garden Book, which describes and contains maps of the 24-zone climate system, can be found at your local library.

Microclimates

Microclimates refer to temperature differences that result from elevation, exposure, thermal capacity and conductive characteristics of soils, presence of ground covers or vegetation, and structures in the environment. Differences of five to ten degrees can occur in short distances.

Warmer sites should be reserved for early blooming species, such as almonds, apricots, Japanese plums, or hardy citrus. Colder locations are more appropriate for apples, pears, quince, European plums, berries, and other late blooming species.

Chilling

Chilling, or the number of hours below 45°F, is an important climatic factor that influences bud break, fruit set, and fruit development. Most varieties require from 200 to 2000 chilling hours in the winter to break dormancy in a normal manner. Insufficient chilling is probably the most limiting climatic factor for sweet cherry, peach, apricot, nectarine, and apple.

Tree Selection discusses chilling requirements for various species and frost management.

Soil

The most important consideration, in any discussion about soils, is good soil drainage. Soils should be very well drained and deep (4–9 feet) for good tree growth, and a minimum of 2.5 to 3 feet for berries and grapes. Shallow, poorly drained sites will produce small, weak plants, with lower yields, that have more pest problems and require special water management practices. With few exceptions, soils through which water drains poorly or stands, promote anaerobic conditions and root diseases lethal to woody plants. Mounds and raised boxes have been used sometimes to mitigate poor drainage in lieu of structural efforts, such as drain tiles, diversions, and backhoeing.

Almost every County has a soil map. In many counties the books can be found in the County library or in the Resource Conservation offices (previously know as USDA-Soil Conservation office). All planting sites should be tested for pH, salt content (Na & Cl), potassium (K), calcium (Ca), magnesium (Mg), and sites near mineral springs should be checked for excess micro-nutrients. Necessary amendments should be applied prior to planting. Most plants, other than blueberries, should have a soil pH close to 6.0.

The addition of organic materials or other amendments to the hole or backfill at planting will not correct or improve soil texture. Organic matter and mulches are better used when applied to the surface of soil around trees after planting and periodically each year. Soil compaction should be corrected by deep plowing or ripping (12–18 inches deep) prior to planting. Ripping into the subsoil will not correct a shallow soil problem.

Water

Fruit and nut plants will do much better if well irrigated, even in deep soils. Fruit trees grow and produce best if you irrigate them deeply several times a season, but the amount you need to use varies with the size of the tree, soil type and depth. As a general rule, you’ll need to water trees growing in a sandy soil every 10 to 15 days because these soils do not retain moisture well. Water trees on a clay loam soil every 15 to 20 days. Clay soils need less frequent irrigations, but larger amounts of water need to be applied to wet the soil deeply. Use the shorter intervals during the hot days of summer, and the longer intervals in spring and fall when the weather is cooler. Trees growing on shallow soils should be watered more often than those on deep soils.

Irrigation discusses the complexities of irrigating your orchard.

Wildlife Protection

Deer (and antlers), rabbits, rodents, birds, raccoons, opossums, squirrels, porcupines, and bears all love some aspect of trees, vines, and other fruit bearing plants. Keep in mind that deer are as good at crawling as they are at leaping and will travel on their bellies if needed. Each pest will challenge your ingenuity and protection startegies.

Most protection efforts focus on excluding deer and rabbits with fences. Six to eight foot vertical fences may be necessary. Narrow wire mesh on the bottom two to three feet of deer fencing effectively excludes rabbits.

Competition

Trees compete with each other, above ground, for light and space and for available nutrients and space below ground. Minimize competition to maximize growth and vigor. A minimum of eight hours of full sun is required. so, clear your site from the effects of large trees and other plants.

Competition is sometimes used to reduce vigor and size, or to enhance flowering. However, this is accomplished through closer tree spacing or high density arrangements rather than leaving existing trees or other vegetation in the landscape at planting time.

Layout

Trees for limited spaces pose interesting challenges, often solved by containers, boxes, dwarfs, multiple varieties per tree, “high density” plantings, cordon and espalier arrangements, and summer pruning techniques.

For a new orchard, map out on graph paper what you have to work with: orientation, available land, existing and future structures, roadways, existing plants to retain or to remove, fence lines, and utilities (water, power, waste, etc.). Consider service or access needs to the site, future orchard or garden expansion, cold and warm areas, and how you will irrigate. All underground lines and fencing should be installed before you plant.

Preparation & Planting discusses planting patterns, how to compute required tree planting space, and other layout considerations.