Irrigation capabilities at the planting site should be considered before selecting trees for a planting site. Irrigation not only impacts species selection, but maximum recommended size of the nursery stock and the tree production method best suited for the site.
With infrequent irrigation, most trees will grow poorly, die back or be killed from lack of water because they take much longer to establish. If trees will be irrigated regularly only until they are established, drought tolerant trees should be chosen, and nursery stock of any size can be planted. If trees receive irrigation during establishment and then regularly during the life of the tree, or if you are planting in the plant's native range and soil type, any tree regardless of drought tolerance can be planted.
Maximum tree size at planting can be determined by knowing the number of months trees will receive irrigation after planting. Trees should be watered for a minimum of 6 months after planting.
Since root growth is slower in colder climates, irrigation during the growing season in the first twelve months would be required to establish a tree in Colorado. For specifics on amount and frequency of irrigation, click here.
Another factor affecting tree size at planting is weed control and the mulch replacement program. If weed growth is not controlled chemically or with mulch application around the tree during the establishment period, it will not allow your newly planted trees to establish as quickly as they should.
While trees are trying to establish, weeds often compete with the limited water supplied to most establishing trees. Removing weeds and grass around the newly planted tree is necessary for the plants healthy transition and survival. Using mulch will help a great deal in keeping weeds under control around the base of your trees.
"Illustrations, PowerPoints or photos by Edward F. Gilman, Professor, Environmental Horticulture Department, IFAS, University of Florida."