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?
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.