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Plant Answer Line Question

Keywords: Thuja plicata, Trees--Diseases and pests--Washington

I have noticed that my old cedar has a very large number of cones on it this year. Several areas of foliage have turned reddish brown. This has all appeared in the past month or less. Some of the other cedars in this area appear to have these characteristics. Is something different going on this year? I am concerned that there may be a disease that is affecting them?

Answer:

Is your tree a true cedar (Cedrus) or a species of Thuja? The Thuja plicata (Western red cedar) in my garden also had a huge number of cones this year, and just like yours, it has some foliage turning reddish brown. This is probably cedar flagging, as described in this Washington State University Extension page. Flagging--the browning of older leaves and twigs--is a common occurrence on western red-cedar and related trees, such as arborvitae. It usually develops in late summer to early fall. Often, very hot, dry weather, followed by rain, will stimulate the sudden dropping of this older foliage.

If the browning were to be widespread, that might be more of a cause for concern. Additional links:

Cedar Flagging from Private Forest Landowners in British Columbia

Date 2019-04-18
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Plant Answer Line Question

Keywords: Chamaecyparis

Chamaecyparis pisifera 'Boulevard' is prone to foliage browning towards the interior of the tree as it matures. What is the cause of this and is there any remedy?

Answer:

I consulted Pacific Northwest Landscape IPM Manual (WSU, 2002), which mentions that lower branches tend to die in older Chamaecyparis pisifera. This resource mentions cedar flagging as one of the cultural or environmental problems which may affect this tree. It is normal for evergreens to shed some old foliage every year, but this may be intensified by stresses like drought, recent or poor planting, root disturbance, or hot wind. Symptoms show up in the form of browned foliage, usually most noticeable in the fall. The current year's foliage stays green at the tips. Remedies for excessive flagging would include close attention to irrigation during periods of summer drought, preventing root disturbance, make sure the tree was not planted too deeply, and improve drainage if the soil tends to stay wet. (Replant onto a berm or raised bed, for example).

Since the browning you have observed is on the interior, flagging would be a likely possibility. Typically, the dead foliage gets blown out of the plant and the plant returns to normal growth in the spring. The following link, to a discussion on University of British Columbia's Botanical Garden Forums, may be of interest to you.

If you think something else might be going on, such as Phytophthora, you might want to bring photos and samples to a Master Gardener Clinic for diagnosis. Signs of Phytophthora begin at the small roots, progressing to larger roots. The inner bark will show a brownish color. Eventually, the foliage will turn color (yellowish to bronze and finally brown). This doesn't sound like your description, however.

Date 2019-08-02
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