We’ve had considerable discussion over on the FaceBook site concerning snow damage to columnar arborvitae. This is a common phenomenon resulting in a condition Holly has dubbed ‘splayage’.
The question, of course, is what to do about it? My standard response to addressing most problems related to winter injury is there are two options: selection and protection.
Selection means putting the right plant in the right place. For columnar arbs this means not planting them in areas prone to wet heavy snow. Here in mid-Michigan we get a wet snow about once every other year. Last winter we had a 10” of snow in Nov. 30 that resulted in a lot of tree breakage, including arbs. The problem is the branch structure of columnar cultivars such as ‘Holmstrup’ or ‘DeGroots spire’ cannot bear up to the snow weight. Remember these are cultivars that were specifically selected for their upright branch habit, this is not the natural branch pattern of the species (Thuju occidentalis or Thuja plicta depending on the cultivar). There are, however, some narrow trees that are adapted to sloughing off heavy snow. For example, most forms of Alaska false cypress (Cupressus nootkatensis) will do well under heavy snow loads. Also, weeping white spruce (Picea gluaca ‘Pendula’) is a good narrow conifer for snowy locations.
Alaska falsecypress (right) is adapted to heavy snow. Notice how snow hangs on other conifers on the left.
But what do you do if you already have a row of columnar arbs and you live in an area prone to heavy snow? Protecting trees from bending over by tying up the upper 1/3 is often the only reliable option. Note that the all ties or wrap need to be removed in the spring. Yes, it’s a lot of work. Makes the ‘right tree right place’ thing sound better. Note that you only need to provide enough support to keep the branches together, you don’t need to wrap the entire tree like a mummy.
I want my mummy… Does this work? Probably. Question is do you want to look at it all winter?
What about repairing damage after trees have splayed? Some arborists I’ve talked to about this problem have had success tying up tops after the fact provided the trees are tied before any new growth occurs and the branches are bent, not broken. It is important to remember that this is similar to situation with standing and guying up trees after a windthrow event. Yes, you can stand the tree back up but how are you going to stop it from happening again? In the case of splayage, you’re into a cycle of tying or wrapping every year.