Landscaping With Hemlocks
Growing hemlock trees is a piece of cake, provided that you take their many needs into consideration when planting them. The question isn’t so much how to plant a hemlock tree as where to plant them. Unlike many other large landscape trees, hemlocks have evolved while growing in the shade of other trees, so you’ll need to choose a place that’s protected, especially against winter winds and drying summer heat. Hemlocks can tolerate a wide range of lighting conditions, but won’t tolerate dry or compacted soils at all. Although there are many hemlocks to choose between for gardeners in USDA plant hardiness zones 3 through 7, many cultivars only do well in a smaller part of that range, so read the nursery tag carefully before bringing your hemlock home.
Care of Hemlock Trees
Once established, hemlocks require little care, but establishing them can be a challenge. They need acidic soils that stay moist, but not wet, and frequent waterings. Like willows, hemlocks are riverbank trees, so if your site is elevated and dry, you may need to add a thick ring of mulch over your tree’s root zone and consider installing a drip irrigation system to keep your tree looking its best. The shallow roots of the hemlock can allow it to topple easily; if high winds are a frequent problem, a stabilizing tree stake should be considered while your hemlock is young. Although the hemlock isn’t bothered by pests or diseases, as a rule, they do have one pest that seems to find them wherever they go. The hemlock wooly adelgid is a small, aphid-like insect that hides inside a woolly sac — the most notorious and troublesome pest of hemlocks. Regular inspections of your hemlock will help prevent serious damage from this pest, provided you check for them at least once a year. October is the best time to treat these pests, using either insecticidal soap or horticultural oil. Imidacloprid is sometimes used as a yearly treatment where adelgids are a constant threat. Occasional pruning of hemlock trees may be necessary when weather-related issues or other damage is present.
