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Pramuk

Hello Bill:

I was searching around for articles on shedding cork oak trees and found one you had written back in 2006. I thought I might write to ask you about these trees.

The scoop: My husband and I have moved to a house-on-grounds at a government-owned property by the north shore of San Francisco Bay.

There is a rather quaint community of old houses here. Lining our side of the street are some amazing OLD cork oak trees. (There is even an old abandoned park at the end of the road that has a gigantic one.)

We moved here in January and had a yard full of fallen leaves and acorns. Though the acorns seemed to have tapered off the leaves seem to fall nonstop. I could actually be out there every day with a rake!

This is a bit distressing to me as I have other things I’d like to be doing besides raking. Also, my husband wants to put in a lawn. It is dirt right now as they had just come through and put in new water pipes across the front of the yard.

I have a suspicion that our big cork tree is not going to allow a lawn to grow underneath it.

Will this thing ever stop shedding? Right now the leaves look 50/50 yellow & green.

Is it possible to plant a lawn without it being bombarded by acorns? If not, what can one have besides dirt?

Regards,

K.I.

Dear K.I.,

Cork oaks (Quercus suber) shed old leaves in spring, as do our native live oaks.

The shedding is more dramatic when the tree is stressed by drought, disease or root damage.

If the trenching for the new water pipeline was within five times the trunk diameter, there is a strong probability that it did significant damage. If so, it will take time and maybe some prescribed supplemental irrigation to see if the tree is able to recover.

In between falling acorns in autumn and falling leaves in spring, there are breaks in the mess-making. So don’t despair. Consider saving those leaves for mulch! The trees thrive on recycling the natural mulch of fallen leaves.

Cork oak is adapted to the Mediterranean climate, with rainfall patterns similar to low-elevation portions of mid-California: dry in summer, but ample winter rainfall.

The California Champion cork oak is in a dry field on the grounds of Napa State Hospital (directly south of the south end of Marshall Street, in Napa). The area is dry in summer, but open and undisturbed.

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That tree has a trunk circumference of 20 feet 5 inches. I wonder if the gigantic one you mentioned is that big.

Turf grass competes with oak roots. The required irrigation invites root disease, so your husband’s plans for a lawn under the tree would be likely to kill the tree or lead to slow decline.

Plant only oak-compatible plants under the canopy and nothing within 10 feet of the trunk. Fall is the best time for this kind of planting.

Many references provide options for a plant “palette.” Here are a few examples:

— “Compatible Plants Under and Around Oaks” (California Oak Foundation)

— “California Native Plants for the Garden” (Bernstein, Fross, O’Brien, Cachuma Press, 2006)

— “California Native Landscapes” (Rubin, Warren, Timber Press, 2013)

— “Water Conserving Plants and Landscapes for the Bay Area” (East Bay Municipal Utility District)

Because of possible root damage, consider irrigating under the canopy but not within 10 feet of the trunk one time in late spring after the soil has fully drained and dried. Then monitor the condition of the tree and call in an arborist for further care.

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Bill Pramuk is a registered consulting arborist. Visit his website, www.billpramuk.com, email questions to info@billpramuk.com, or call him at 707-226-2884.

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