Marin Bonsai Club

Greg McDonald put on a free-wheeling, engaging and inspiring presentation on California oaks for bonsai at our May meeting. With several examples illustrating the styling techniques he uses to create his exceptional bonsai, as well as those from members, Greg led the audience through his process which is a bit unconventional.

The following are this member’s highlights from the meeting:

• Greg considers Coast Live Oaks the crown jewel of oaks.They grow well in our part of the world, are deciduous and so give a great silhouette view in the winter, and are reasonably easy to maintain as bonsai.
• He noted that climate change is presenting new problems for oaks with fungus and disease becoming more common with unseasonable rain and heat.
• Greg has found some of his best trees in horse pastures where they get kicked around and rolled on, giving them lots of dramatic shapes.
• Blue Oaks also make good bonsai, but are a little trickier to maintain to maximum health.They need lots of heat, so Novato is good, Mill Valley not so much.
• Valley Oaks and other species make good bonsai, but Greg had less history with those.
• Highly recommended: “Oaks of California” by Bruce M. Pavlik, Pamela C. Miuck, Sharon G Johnson and Marjorie Popper as a primer for all California oaks. It is old and out of print, but relatively easy to find.

Collecting Oaks

• Seedlings are abundant and a good way to start an oak tree, but it will be a couple of decades before they are ready to be bonsai.
• A light wrapping of raffia on seedlings will protect the young trees, especially if they are wired and bent into shape.
• Collected trees should be pruned back to a manageable size in the fall, then when the winter rains start it is safe to collect them. Greg has not found that cutting the tap root causes any problems. He defoliates the trees before digging, then prunes back again the first year out of the ground.
• Other than crotch growth and a few truly unnecessary branches Greg does not prune the trees for the first few years out of the ground.
• All young trees will grow faster in a box created with plywood. A box does not subject the roots to as much temperature change as a ceramic pot, and gives the roots lots of room to grow and nebari to develop.
• Great tip from Julius: he uses or makes boxes with side handles so they are easier to move around.
• Boxed trees can be grown in 100% pumice or a dry mix with lava and some Akadama.
• Apply shredded sphagnum moss to the top of soil to protect new surface roots.
• Let new material run for a few years without pruning to allow the tree to gain maximum strength and roots to become well established.

Defoliating Deciduous Oaks (and some other tree species like Trident Maple)

Greg introduced a technique new to most of us where ALL of the leaves are taken off the tree to spread the production of the powerful growth hormone Auxin evenly throughout the tree. There are several conditions that make this technique successful.

• The bright green or red tips of branches indicate an energy deficiency within the tree. Do not defoliate before the leaves have hardened off: more firm and deeper color, waxy feel.
• This procedure will not be done every year, only when the tree seems to be weakening or needs an extra growth push.
• Take ALL leaves off or the energy in the tree will go to the remaining leaves and not produce as many or as strong buds, which is the goal.
• Some light wiring can be done at the same time, but there is a risk of inhibiting and damaging the desired new buds.
• After defoliation the tree will not need much if any water because there is no photosynthesizing happening. Watch trees closely – everyday – to see the progress of new buds developing. Keep in part shade for the fist month.
• These trees will want a lot of sun while regrowing, but not the hottest place in your yard.

More typical defoliation of Deciduous Oaks

• Oaks, like any other species will benefit from partially defoliating once or twice during the growing season in order to let in light for the lower branches. May is an excellent time to do this if new growth has hardened off.
• A 20% reduction is typical, but depending on the health and vigor of the tree more might be needed to bring light to lower branches.
• Leaves my be removed completely or, for a more attractive method Greg recommended a technique used by Bjorn Bornholm where the leaves are gently folded in half along the vein then cut at a diagonal to remove approximately 1/2 of the leaf.This technique is particularly useful if the desire is to open the interior, but allow more leaves to remain on the tree.
• Please note: These techniques should only be applied to healthy trees and at the appropriate time of year. If you are uncertain about using this technique on your tree, check with someone with experience in these methods of bonsai development.

Protecting Deadwood: Treat deadwood areas with a lime sulfur application to prevent rot, which oaks are prone to. Some rot can be good, but not to the extent it weakens or kills the tree.

Final Note: Greg held two workshops during his Bay Area visit and will be visiting frequently during the year. Members interested in participating in workshops outside our regular meeting times on all tree species should notify Candace of your interest so she can alert members to opportunities as they present themselves.

– Candace Key