Planting cedars in clay

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Q: I am wondering about planting some emerald cedars in clay soil in north-central British Columbia. What is the best time to plant, and should they be bagged in winter? I don’t know what zone this is, but it wouldn’t be colder than Alaska. Would it be best to start with smaller trees, rather than large ones?

North-central B.C. is a huge region that includes microclimates from zone 1 to zone 5 – Alaska has about the same variability. The short answer is that I wouldn’t plant emerald cedars (Thuja occidentalis ‘Smaragd’) in this region at all, because it is (mostly) dry interior plateau, with emphasis on the dry. 

Our humidity is very low year-round, and this is hard on cedars, which are coastal rainforest plants adapted to high humidity. In heavy clay soil, the roots will probably rot during rainy weather, while the tops desiccate and burn in winter winds.

If I had to plant them in clay I would do so early in the spring, amending the clay as I describe in Planting in Clay Soil, mounding them up a little bit but not too much, so the roots are not sitting totally in water but also not sitting up on an exposed mound over the winter. Mulch to keep the moisture in the top layer of the soil, keep them well watered right up until freeze-up and hope for the best.

I am not a fan of wrapping with burlap or anything else. What is the point of planting an evergreen for four-season interest and then wrapping it in ugly burlap? Columnar forms of Picea glauca (white spruce) or P. pungens (Colorado spruce) would do better, or something deciduous that can be pruned to the width desired, or a fence with vines.