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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Nov 04

Falling Leaves

Posted on November 4, 2016 at 9:13 AM by Ann Vallee

by Charlene Burgi

Fall color in Eastern Sierra
 Autumn in the Eastern Sierra
Autumn is a beautiful time of year. The crisp air, and the brilliant shades of yellows, oranges and reds that assault our vision whether we drive through town or country—autumn has its own kind of charm.

However, autumn has another element we must deal with: falling leaves. As gardeners with deciduous trees, we must decide how to manage falling leaves. Leaving them as mulch or leaf mold is one idea that works well. The decaying leaves will break down and add nutrients to the soil while providing a protective layer for roots in cold weather. The leaves can also aid in abating weeds in the spring. If this is an option you chose to employ, remember to pull the fallen leaves away from tree trunks to avoid build-up around the base of the tree.

On the other hand, allowing some leaves to remain on the ground can be harmful. For example, many fruit tree leaves can acquire a disease commonly known as shot hole blight, scientifically known as Coryneum blight. This disease is carried by spores that cause lesions along the twigs; in the spring it presents as black spots on the buds and young leaves. Wet conditions cause the spores living on fallen leaves left on the ground to multiply and cycle back into the tree. It is imperative to clean up any fallen leaves if leaves on your trees look as if they were hit by a shotgun! This also holds true for the deadly Phytophthora that plagues our beautiful oaks (genus Quercus) and tanbark oaks (Lithocarpus)

lemon leaf drop
 Leaf drop in light-deprived lemon
Other types of falling leaves also can be a cause of concern. A month ago, I could not resist the temptation to purchase a Meyer improved lemon. The plant had a magnificent shape, and foolishly I gave into purchasing it as if it were a puppy begging for a new home. Growing citrus in the winter here in Lassen is a challenge; citrus trees must be treated as if they lived in European orangeries, where they were moved in and out of doors with the seasons. This little lemon did not find its home in such luxury but was placed inside the house to protect it from the bite of falling temperatures. My mistake was to put it in a room that lacked enough foot-candles of light for citrus. (Different plants require different amounts of light, which is measured by foot-candle or lux.) Lacking the needed light, the citrus began dropping its leaves. The remedy is moving it to a bright window until the weather warms up. Those of you brave enough to attempt growing Ficus benjamina will recognize this type of leaf drop, as this plant also requires extreme high foot-candles to be happy.

Falling leaves. They can be a source of pleasure, a chore or a mystery depending on the circumstances. Nonetheless, they are part of nature that gardeners embrace.


Anonymous User
November 4, 2016 at 11:14 AM
my 10 year old meyer lemon (always flourishing), produced brown drooping leaves recnetly. Could be an attack on the roots, gopher, hard to say. We rulled out lack of water and fertilizer. Garner said he as seen more of this around. (woooded area of San RAfael). Cut off the elaves and will see what happesn. Pessimistic. Any thoughts?
Anonymous User
November 6, 2016 at 5:02 PM
Can you tell me if I should rake up Persimmon leaves or leave them on the ground as you suggest in your newsletter?
Charlene Burgi
November 8, 2016 at 9:18 AM
It is difficult to diagnose a problem without seeing it first hand. To be on the safe side, I would contact the Marin Farm Advisor as citrus in California are subjected to a disease called huanglongbing that started in Southern CA and continues to spread north. Diseased trees need to be addressed as the Asian citrus psyllid carry bacteria infecting trees and can fly to other nearby citrus and injecting those trees with this deadly disease. Again, get this checked out!
Charlene Burgi
November 8, 2016 at 5:02 PM
Persimmon leaves are not a problem as mulch. The leaves are high in vitamin C...Do you like tea? They might be a nice addition to your tea leaf reserves!

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