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Title: Propagation container and timing of propagation affects growth and quality of oak seedlings

item Fare, Donna

Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2012
Publication Date: 3/1/2013
Citation: Fare, D.C. 2013. Propagation container and timing of propagation affects growth and quality of oak seedlings. Journal of Environmental Horticulture. 31:43-48.

Interpretive Summary: Oaks are one of the most important landscape trees and account for more than $98 M in annual nursery sales. Many oaks are now propagated in containers instead of the field or beds, which reduces root loss, transplant shock, and mortality. The root architecture can be impeded when oak seedlings are grown for an extended period in small propagation containers before re-potting into larger nursery containers. This research shows that a larger propagation container coupled with changing the sowing period from March to June resulted in seedlings that were similar in height and caliper growth as plants from early-sown acorns, as well as a desirable root system, in half the amount of production time. When growing or purchasing container propagated seedling oaks for re-potting, nursery managers need to pay special attention to the seedling root systems. Seedlings that have been left in small propagation containers for an extended period can have excessive root circling or kinked or matted roots on the sides and bottom of the container. This can predispose plants to future root problems in the production or landscape phase.

Technical Abstract: Two experiments were conducted to determine the container effect and the timeline of seed propagation on germination and subsequent shoot and root development for container-grown oaks. Quercus nigra and Q. texana had equal or better growth and better root ratings when acorns were sown in Anderson tree bands compared to five other traditional propagation containers that had at least half the root volume. Germination percentage of Q. bicolor, Q. phellos, and Q. shumardii was similar at 10 weeks after sowing whether acorns were sown in March, April, May or June. Q. bicolor and Q. phellos acorns sown in March had similar height and trunk growth during the 30-week growing period in year 1 as acorns sown in April, May, or June that only had a 25, 20, or 15 week growing period, respectively. Q. shumardii seedlings had greater shoot growth when acorns were sown in April or May compared to March or June. However, there was no difference in trunk diameter. By the end of the second year, Q. shumardii repotted into #3 nursery containers had similar growth among all sowing dates. Though some statistical differences occurred with shoot and root growth during the second year for Q. bicolor and Q. phellos, these differences did not appear to be the result of propagation time but probably a result of genetic variability.