Field-grown trees and shrubs are generally grown in rows to facilitate planting, weeding by hand or mechanical cultivation, and cultural operations such as grafting and pruning. Most weeds are controlled in established plantings by cultivation and application of preemergence herbicides, but perennial weeds need to be controlled before the crop is planted.
Crop Rotation
Sometimes the field is fumigated before planting. During the growing season, cultivation, herbicides, or other control methods are used. After the crop is harvested (either bareroot in winter or potted in spring), the field is planted to a cereal crop in fall (barley, oats, or wheat) and harvested the following spring. Herbicides can be used in the cereal crop that will reduce weed problems in the next crop of trees and shrubs.
Solarization
Soil solarization is a valuable tool to clean up a site before a fall planting (see "Solarization" under GENERAL METHODS OF WEED MANAGEMENT.
Cover Crops
Cover crops, especially winter annuals such as barley, oat, wheat, or combinations of these with rose clover, may be planted between tree rows in early fall. Cover crops reduce erosion and help maintain soil organic matter when the cover is worked into the soil in the spring. Mow the cover crop and work it into the soil before it seeds to reduce competition with the marketed crop.
Mulches
To reduce weeds in field rows, cuttings can be planted through holes in paper mulch. After planting, organic mulches (e.g., bark chips) can be applied around the plants and between the rows. Organic mulch must be deep enough to shade out all weed seedlings as they germinate. Keep organic mulch back some from basal stems of the crop to avoid promoting crown decay. Geotextile can be placed along the sides of newly planted stock. The geotextile materials must be placed close to the plant to reduce the number weeds will grow around the base of the plant. It is often beneficial to combine geotextile and organic mulches to achieve good coverage and reduce ultraviolet degradation of the geotextile.