Mid-season Pruning Affects Cold Tolerance of Abelia Cultivars in Central Georgia

in HortScience
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  • 1 University of Georgia, Horticulture, Griffin, GA, 30223

While the recommended time to prune abelia is before spring growth initiates, the actual pruning time is often variable and dependent upon labor and plant appearance. As abelia suffers from freeze damage north of zone 8A, pruning may have an impact on the level of freeze damage. Six Abelia genotypes were established in replicated field plots in Griffin, Ga., in 1999. On 3–4 July 2003, half the individuals of each genotype were severely pruned (75% of growth removed). Subsequently, 80 uniform-sized stem tips were randomly collected from plants of each genotype–treatment combination once per month from Oct. 2003 through Apr. 2004. Stem sections were exposed to predetermined temperatures ranging from –3 °C to –27 °C in a temperature bath. The number of stem sections killed in each of two replications out of four possible stem sections was recorded (0 = none dead; 4 = all dead). Data were analyzed with SAS using the Genmod procedure to acquire seasonal results as well as with PROC GLM and means separation to acquire monthly results. Using the Genmod procedure, all genotypes with the exception of `Canyon Creek' were significantly more cold tolerant in unpruned compared to pruned treatments. In this study, Dec. 2003 was the first month with temperatures below freezing at the test site. Proc GLM analysis indicated a significant difference between the pruned and unpruned treatments in Dec. 2003–Feb. 2004. Results of the Proc GLM analysis for the months of Oct. and Nov. 2003 as well as Mar. and Apr. 2004 were nonsignificant (P < 0.05) due to an absence of cold acclimation. These results indicate that mid-season pruning of Abelia genotypes can significantly reduce cold hardiness and lead to serious stem dieback in pruned plants.

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