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Monday - October 08, 2007

From: Bonn, Germany
Region: Other
Topic: Propagation
Title: Western red cedar (Thuja plicata) frost tolerance, making cuttings
Answered by: Nan Hampton


Dear Madam or Sir, It would be very kind, if you could answer my questions about the “Thuja Plicata atrovirens” alias “Western Red Cedar”. I need the information because a good friend of mine planted several remarkable cedars in his garden. It would be a pity if they are damaged by an incorrect treatment. First some information regarding the cedars: They were planted in 2003 and 2005. The length of the plants was approximately 7 ft. Now they are ca. 16 feet. They are supposed to grow to a length of 19 feet. The calibre at the ground is around 6.5 ft. The green part has 1 ft. The location is very sunny. The ground has big part topsoil, turf and sand. When they were planted a distance of 2.6 feet between the logs was kept. They already look like a hedge. No cuttings have been taken so far. Climate: Continental Europe / Central European My questions: When would be the best time to take cuttings? How often is it possible to take cuttings during a year? How much of the green part can be cut? How frost resistant are the roots? We plan to build a slope near the cedars and for this reason the roots, at one of the sides, will only have 1 meter (3 feet) soil (from the logs to the border of the slope). Can the roots possibly compensate for the frost risk exposed to the part, which is not experiencing optimal protection? Besides the aforementioned questions I would be very interested in further information regarding the Red Western Cedar. I am looking forward hearing from you and thank you in advance. Best regards


It sounds as if your friend's western red cedars are doing very well to have doubled their height in four years time.

Thuja plicata (western red cedar) is native to the northwestern United States, Canada and southwestern Alaska.

I am including references with more information about Thuja plicata from Washington State, The Gymnosperm Database, Glacier National Park and the Center for Wood Anatomy Research of the US Forest Service.

When you speak of taking cuttings, I am not sure whether you mean: 1. when and how to prune the trees for shaping, or 2. how to take cuttings for propagating the trees vegetatively.

Most sources say that T. plicata doesn't require pruning but will tolerate it if you want to make it a different shape or size.

There is lots of information about propagating T. plicata from seeds, but very little about vegetative propagation. The one source I found, Plants for a Future, recommends taking cuttings of half-ripe wood, 5-8cm with a heel in July/August and rooting in a shaded frame. Roots should form by the end of September but it should be overwintered in a frame. Alternatively, cuttings of almost ripe wood, 5-10cm with a heel, can be taken in September and rooted in a cold frame. Roots should form by the following summer and be planted out in autumn or spring. Here is a little more information about Plant Propagation by Stem Cuttings: Instructions for the Home Gardener.

With regards to the frost tolerance of the roots, Western red cedar survives in Ketchikan, Alaska with an average minumum temperature of 28.3 degrees F. in January, which is not too different from Bonn, Germany where the average minimum temperature in January is 31 degrees F. Unless you are exposing the roots completely, I would think that they could withstand the frost as long as they had at least a meter of soil covering them since I wouldn't think the soil would freeze down to 1 meter in Bonn's climate.




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