This week I went to an old landscape along the Missouri River. It was filled with evergreens. Old, mature dwarf Alberta spruces, boxwood hedges, screens of arborvitae, and the occasional holly filled the landscape with green color year round. I was there to consult on the landscape-many of the evergreens had issues. I saw fungal infections on the arborvitae and the spruce, over-mulching on the boxwoods, and over pruning on everything.
Those who know and work with me know that I dislike shearing. Shearing is the practice of using powered clippers to routinely shape and trim shrubs unnaturally. Do not get me wrong, I think topiaries and spirals are awesome, and I even maintain some in Kansas, but I use proper pruning methods instead of the hard cuts of shears. I train my helpers to use pruners and hand shears to lightly clip and prune shrubs to shape.
These evergreens had been over-sheared and at the wrong time. There was recent growth that had been frozen and killed by our recent cold snap. Evergreens should not be pruned past October 1st to prevent possible freeze off of new foliage growth from pruning. Pruning activates chemicals in the plant that promotes new growth when the plant is actively growing.
Another problem I noted was over-mulching. There was 3 to 4 inches of mulch on top of the plant stems of the boxwoods, and soil covering their stems as well. Planting too deep is another issue that can weaken and kill plants much before their time. Mulch should be 3 to 4 inches thick around the plants, but with a space away from the stems, leaving room for air movement. Mulch should never be applied inside of multi-stemmed shrubs or perennials; this can suffocate roots and stems, and cause adventitious roots to form, which are not healthy for most plants.
Landscapes with many evergreens should use a foliage protector like Wilt-Pruf that prevents foliage from drying out and desiccating in our winter winds. Bronzing of boxwood and arborvitae foliage is a normal occurrence and the plants should green back up in spring when normal growing conditions resume.
Remember with evergreens, prune correctly and at the right time, protect from winter desiccation, and plan for spring and summer protection from insects and diseases.