Living amongst the oaks

What is more characteristic of the California landscape than the majestic oaks that abound throughout our Golden State? They range throughout our state from high desert slopes to the Pacific shores.

The relatives of modern oak species contributed to the landscape of prehistoric California more than 20 million years ago, and the state has over 20 species of indigenous oak species.

As California’s population has grown, we have moved into territories that were once thick with these ancient trees. When the first settlers in wagon trains moved over the Sierra Mountains, they viewed on the valley floors a sea of oaks as far as they could see.

Since the days of tree-studded oak forests, we have lost more than 90 percent of oak trees with those remaining in isolated patches. The remaining range of oak hardwood shows clearly that the last hundred years of human habitation and its ecological impact has affected the fauna and flora that once lived in cohabitation in these special woodlands.

Oak woodlands are a unique ecological resource. There are over three hundred species of animals, bugs, fungi, vertebrates and a wide variety of mosses, lichen, ferns, grasses, shrubs and perennial plants that coexist in this unique and natural-forested world.

The oak trees that have long been in the history of California’s making are now at a pivotal point for survival.

As man moves into the backcountry throughout the state, agriculture and home development threaten the hills and dales of oaks. Vast amounts of oak are also threatened by climate change. Under normal weather patterns, oaks drink rainwater in the winter and run dry in the summer. However, since climatic conditions haven’t been normal, oaks have been under water stress from the past dry rainfall years up until this current rainy season of 2019.

When trees of any species go into stress mode, their vulnerability to outside factors like bugs and diseases can alter their normal physiological growth, making them more prone to invasion by opportunistic bugs.

One of these plaguing insects, originating all the way from Central America, is the gold-spotted oak borer. Now in California, this beetle is setting up large populations and doing some devastating damage, including killing our native oak woodlands here in the Southland.

If you have oak trees on your property or want to work with the conservation of their future, the following are some do’s and don’ts about their care:

Root zones: Oak root systems are fairly shallow and extend far beyond the canopy drip-line. This means that digging, grading, trenching or covering this area with asphalt or concrete can have serious effects for the root system to breathe and carry on their natural process.

Changes in Grade: Mounding of soils on top of an existing grade can alter the intricate mycorrhizae fungi world that is constantly working to support an oak tree. Soil compaction must be avoided whenever possible.

Paving around oaks: I have often seen non-porous materials used around oaks that can have long-range ramifications. This can start the decline of an ancient oak tree just by parking vehicles under it and compacting the soils.

Included bark: This is an area that one should be aware of and not only on oak trees but all trees out in the landscape. It is where two branches fork off one another, and there is not a solid bond with each trunk. As result, a split can occur and/or a cavity can form that may fill with organic matter or water. Over time, the cavity can turn into a breeding place for decaying fungi. The decomposition of leaves and moisture creates a compost-like pile. I have gone out on many oak consultations and have found deep cavities within this area rotting away. When this occurs, the trees internal strength is jeopardized and is called “heart-rot.”

Pruning of oaks: Don’t over prune oak trees. The canopy of oaks is like a huge umbrella. The leaves create a massive blanket to shade the interior branches, trunks, and twigs from the hot summer sun. When this protective shade is reduced or overpruned, the interior branches can sunburn or sunscald. When bark is sunburned, the interior cambium tissue, found just below the bark, is left with less protection. The cambium is the transportation system of water, sugars, and starches that are translocated throughout the entire tree. The care and stewardship of oaks is both an art and a science, and the trees should be cared for professionally.

Planting under oaks: Since oaks can provide a shady area below the canopy, I see all too often the planting of shade-loving plants to create a shade garden of azaleas, camellia’s ferns and other high water-demanding plants. The extra irrigation to support these plants in the summertime (when oaks like to be on the dry side) can set up pathological conditions and lead to oak tree fungus and decline over the years. Also, remove all vines and ivies from growing up into the canopy of oak trees because it can cause great harm.

Environmental changes around oaks: Go out to a native woodland area and view what’s going on. Learn from nature what you see and adapt your landscape to match or mimic those conditions. The oak leaves that fall from the trees is beneficial, and there is no need to blow them off the surface of the soil. These leaves are a part of the trees good health and added nutrition.

Rainfall about old oak trees: This winter’s abundant rainfall has put a lot of old oaks trees in jeopardy.The heavy rains have saturated the soils to a great degree. The combination of an oak’s weight in volume along with softened soil can lead to some trees toppling over. Trees are a wonder of nature. They must be thought of as an organic structure susceptible to exterior factors of wind, rain, sun, soils, weather and all the elements that surround them.

Stewardships of oaks: We should appreciate that trees are like people: no two are exactly alike. Some are strong, vibrant, healthy with vim and vigor, while others are not so. With this understanding, trees are a liability and safety is a priority around people’s homes. People care for their cars with lube, oil, gasoline and maintenance; people brush their teeth daily and go to the doctor for an annual checkup. The trees that surround us daily need care and a stewardship program that they deserve.

As the San Diego adviser for the California Oak Foundation, I am concerned for the future of oak trees here in California, for they need our help in sustaining them in nature’s fabric. What would California be without our oaks?

The California Native Plant Society has started a program called Re-Oak California. The program’s objective is to collect in the fall oak acorns of various species endemic throughout the state. We here in the Fallbrook area have Quercus agrifolia- and Quercus englemanii, a rare and endangered oak.

I hope you will join me in this worthy oak tree movement for the region and our state. The acorns collected in the fall will be sent to a San Diego nursery where they will be planted, germinated and grown up to a seedling size.

When these young oak trees are ready and large enough, they can be adopted and planted in needed areas throughout San Diego County. I would be happy to have you on board, for this beneficial program not only for the area, region, and environment but for the earth.

Arbor Day in California is celebrated March 7-14. So pick up a tree, dust off your shovel and plant trees. You can also join our local Save our Forests group in Fallbrook and be part of our town’s ongoing planting and caring for trees.

“Never doubt that a small group of thoughtful, committed citizens can change the world, for it’s the only thing that ever has.” – Margaret Mead

Roger Boddaert, Maker of Natural Gardens, can be reached at (760) 728-4297 for assistance, consultations and creative landscape designs and professional tree care.