Help! The Leaves on My Evergreen Toyon (Ceanothus, Coffeeberry, etc.) are Turning Yellow!

 

Yellowing leaves on California coffeeberry (Frangula californica)

It’s
May, June or early July.  The days are
warm and the garden’s transitioning from spring to summer.  Suddenly, you notice yellow leaves on your evergreen shrubs.  If the shrubs have been thriving all spring, the
appearance of yellow leaves can be surprising and alarming.

Take
a deep breath.  Then carefully examine
your shrub.  Are the yellow leaves larger
and older?  Lower on the branches (closer
to the trunk)?  Are the yellow leaves
scattered throughout the foliage (not concentrated on a single branch)?   Are healthy new leaves emerging?  If so, your shrub is likely exhibiting a
normal seasonal process – summer leaf drop.

 

Note that the larger, older leaves are yellowing

 on this 'Ray Hartman' ceanothus

 

 Evergreen
plants lose their leaves, just like deciduous plants.  But they lose them less frequently – and not
all-at-once.  Shedding old leaves is but one
way that woody plants conserve their resources. 
Old leaves are often less productive. They are also more likely to be
unhealthy.  In short, senescent leaves
become a drain on the plant. They simply require more resources than they make,
an unfavorable cost-benefit ratio.

And
so, evergreen plants shed their old leaves, but not haphazardly.  They usually recycle mineral nutrients and
plant chemicals before they jettison an old leaf.  The declining leaf then produces less green
chlorophyll, becomes yellow (or orange) and ultimately separates from the
branch at a special site called the abscission
layer.  The process is relatively safe
and painless for the plant; the abscission layer ‘walls off’ the leaf scar on
the branch, preventing disease.   And the
senescent leaf simply drops off – its work complete.

Older toyon leaf turning yellow & red.  Note disease.

 

Evergreen
plants drop their old leaves at different times of the year. Some lose them, a
little at a time, throughout the year. 
But many large California native shrubs, particularly those from the
chaparral, lose their leaves in late spring/early summer, before the dry season
begins in earnest. This allows them to channel their energy into summer growth
and drought avoidance.  So summer leaf
drop is perfectly coordinated with our challenging mediterranean climate.

Coffeeberry leaves provide summer leaf color.

 

So
what’s a gardener to do?  If you have a
big garden event that requires an immaculate garden (a garden wedding?  a visit from the queen?) then gently remove
the leaves just prior to the event.  This
will improve the appearance and won’t harm the plant.  Otherwise, sit back and let nature take her
course.

Enjoy
a bit of ‘summer leaf color’.  Let the
leaves fall naturally, creating a native leaf mulch to support your many soil
creatures. Savor the yearly changes associated with our natural heritage.  Summer leaf drop is, after all, part of the
cycle of seasons in a California native garden.

 

 

 

 

We
welcome your comments (below).  You can
also send your questions to: mothernaturesbackyard10@gmail.com