Maintenance timing matters as well: early spring or late summer pruning or shearing can stimulate new shoots that will get damaged if there’s not enough time to harden off before a frost or freeze. ![]() The degree of damage can vary by exposure (sun to shade) and the relationship to topography or structures. Boxwood with southwest-facing, full sun exposure seem to be at greater risk of damage. Buxus species and/or cultivar cold hardiness is important to note, as there is a fairly broad range of cold tolerance among species. We divide cold damage into two camps: frost damage that occurs in fall or spring, resulting in light die-back of the newest growth and more severe freeze damage because of unusually low or prolonged cold temperatures. We all love boxwood for the beautiful evergreen (and deer-resistant) foliage, but winter injury and discoloration can certainly occur. In this newsletter and the next, we’ll discuss some common issues – fitting, considering the winter we’re having (with more yet to come). ![]() Boxwood planted in a more protected area including the north or east side of a structure are more apt to avoid bronzing. Multiple freeze/thaw cycles and south to southwest exposure present the greatest chance of bronzing. Full-sun exposure tends to result in a greater degree of discoloration – and if in partial shade, the “sunny” side may be bronze. The desiccating effects of wind and sun can result in bronzing as a stress response, especially if the plant is already drought-stressed. Bronzing is easily distinguishable from other issues, as most diseases either attack lower foliage, cause defoliation, or result in an obvious discolored branch or sector of the plant, not a relatively uniform color change across the surface - dig into a bronze boxwood and you should find plenty of green. Whether Buxus, Chamaecyparis, or other species, this pigment change is not harmful to the plant. The discoloration can appear on just the tips, one side, or the whole plant. Drought stress resulting in decreased transpiration can exacerbate the situation. Zerotol 2.0 (hydrogen dioxide + peroxyacetic acid) is a sanitizer that is available for use by commercial growers.Several species of broad-leaved evergreens and conifers exhibit winter orange-to-purple coloration, referred to as "bronzing." The production of chlorophyll slows, so purple-to-orange anthocyanin pigments present in the leaves are more visible. Oil tools after use to prevent corrosion. Sanitizers available for home use that are effective for the boxwood blight pathogen include a solution of household bleach ( 1 part bleach : 14 parts water) or Lysol Concentrate Disinfectant (at label rates). Pruning tools should be dipped in a sanitizer for a minimum of 5 minutes between sites or between blocks of plants. After possible exposure to boxwood blight, sanitize clothing, shoes and tools. Avoid working in plants when they are wet. Results of the study can be found here: 2012 study, 2013 studyģ. North Carolina State University has identified several cultivars that have low susceptibiity to boxwood blight, but a fully disease resistant species or cultivar has not yet been identified.īoxwood Cultivars with Low Susceptibility to Boxwood Blightī. Resistant plants can still carry the pathogen and should be inspected carefully before purchasing and planting. Plant Resistant species and cultivars: Note - Resistant does not mean immune.
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