Skip to main content
All Posts By

Maxine Cass

A Venerable Tree, Oregon White Oak

By Beet 2025 01 January

Oaks, including Oregon white oaks/Garry oaks (Quercus garryana), are science’s superstar trees. They are often described as one of the best lifestyle trees on the planet for the number of species that live on, in, or interact with them. Figures differ, but more than 200 caterpillar species use oaks as a host plant. More than 345 animals, reptiles, birds, insects, plants, fungi including truffles, a mistletoe (Phoradendron villosum) that grows only on Oregon white oak, and even algae interact specifically with Oregon white oaks.

Doug Tallamy, professor of Entomology and Wildlife Ecology at the University of Delaware, is a fierce advocate for native plants of all kinds. His book, The Nature of Oaks: The Rich Ecology of Our Most Essential Native Trees, traces oaks month-by-month through the year. Oaks do a lot of growing underground while producing a rich environment for the creatures dependent upon them, he says, and aren’t overly noticed by humans. Tallamy lauds oaks as a powerful keystone species. These are “native plants critical to the food web and necessary for many species to complete their life cycle,” as noted by the National Wildlife Federation.

Constance A. Harrington, a US Forest Service researcher at the Pacific Northwest Research Station in Olympia, Washington, is an Oregon white oak expert. Her research has confirmed that white oak, a long-lived species, is not shade tolerant and needs sun and space. When free to grow, they can grow from 50–90 feet tall. Drought tolerant white oaks, she says, can live in either cool, humid or hot, dry conditions such as we have in the Rogue Valley (-30° to 116° F.). They have a deep taproot, roots flexible enough to grow around rocks and are wind resistant. The greater the branch spread that results in a large, wide crown, the more acorns will be produced, Harrington notes.

Many white oaks are old and established. The heartwood is hard to core with a tool that removes a wood sample to count the number of tree rings and age a tree. The height of a white oak or the density of its branches do not tell its age. In the Rogue Valley, it’s assumed that mature trees may be up to a couple of centuries old or more.

As the tree bark ages, it gets rougher and from a distance can look like lizard skin with chalky hieroglyphics! Oregon white oaks, as opposed to California black oaks (Quercus kelloggii) that are at the northern edge of their range here, tend to have whitish bark. Leaves are an easy way to determine white versus black oak: white oak leaves are lobed (rounded) where the leaf juts out; black oaks have pointed tips.

But why get excited? Traveling around the Rogue Valley, there are groups or swaths of oaks, often enough appearing mixed in with other trees or shading cows in a pasture. Why are Professor Tallamy in the East and Connie Harrington in the Pacific Northwest sounding a loud alarm?

It’s a crisis. The Oregon white oak/Garry oak has been a disappearing act since non-Indigenous settlement began in the Pacific Northwest more than 200 years ago. Estimates for the somewhat scraggly-limbed but lush, leafy trees are that less than 10% (6% in the Willamette Valley) of the Quercus garryana species survives two centuries on, mostly in sparse fragments on the landscape.

What happened? A Washington state guidance paper published in 2024 identifies “agricultural expansion, suburban and urban development, fire suppression, and conversion to more commercial Douglas fir” (that overgrow oaks with a higher canopy) as reasons for declining survival. Invasive species such as Scotch broom, Himalayan blackberry and English hawthorn and others have severely encroached on oak stands.

Documented Indigenous use included frequent, non-severe burning to improve oaks’ acorn crops and perhaps to gather prey animals for hunts. The Willamette Valley has 6% of the pre-settlement oaks and their successors left. The drier Rogue Valley, slower to remove oaks from traditional stands, has more remnants although no one is sure what percentage of Oregon white oak remains here.  Most Oregon white oaks are on private property in this state.

Protection of existing oaks and encouragement of seedings are a dual strategy to save the species:

Existing Trees

Don’t remove a live oak tree (if possible). If a tree has to be removed in an open area and there’s a choice, try to preserve the oak. When you “release” an oak or small stand of oaks this way, the oaks have a chance to thrive.

Don’t overwater! Oregon white oaks are heat and drought adapted, expecting toasty temperatures when they have transitioned from spring growth to summertime acorn grow-out. Watering will depend somewhat on the oak’s location and your landscaping.

Oregon white oak roots extend beyond the drip line (the edge of the leaf canopy). Any machinery driven across the roots may damage or eventually kill the tree. So might damage to the trunk base by a mower or weed trimmer.

Harrington’s research indicates that the instinct to prune Oregon white oak so that no dead-looking or bare-seeming branches remain works against white oak survival. Sideways epicormic or “pin” branches rise from buds underneath the bark and directly help the oak build its crown.

Don’t worry if your Oregon white oaks produce wildly different numbers of acorns per year. A year of heavy production – filling the ground below and around the trees – is called a mast year. There are many theories why production varies, but it’s assumed that this survivor species of oak has a strategy.

Oregon white oak, a hardwood, tolerates lack of water, and its drought resistance means that it can withstand wildfire better than many conifers, for example. If its landscape is prepared for a wildfire, chances are that the oak will experience a less severe fire (as Indigenous peoples did by burning small areas quickly and less severely).

New Oregon White Oaks:

Many people struggle to get new Oregon white oaks to survive. The acorns are beloved as food by deer, squirrels, Steller’s jays, acorn woodpeckers, and any creature that can crunch open the acorn shell. Squirrels cache acorns in the fall to dig up later. Whether dug in by squirrels or finding ideal soil conditions to nestle in unmolested by critters, the “naturals,” – seedlings that grow without human intervention – are considered by foresters to be the hardiest and probably healthiest of white oak seedlings.

As gardeners, it can be fun and challenging to gather intact (no holes drilled through the shell) acorns and plant them. The long taproot establishes quickly so digging up seedlings, whether naturals or planted by you, may not work. Harrington’s advice is if you want to seed, do so in the fall when the acorns are ripe because oak plant roots get established in the fall. Plant the acorn deeply (4–6 inches) and/or use a metal mesh cage to reduce animal theft.

Soils should be appropriate (Oregon white oak grows mostly in clay soils in the Rogue Valley). Water seedlings but don’t overwater (as with any dry-loving native plants).  Squirrels or birds dropping acorns may decide to replant for you! Lastly, oaks are slow growers. Planting an acorn now is a gift to your grandkids.

A Word about Oak Diseases:

What are the round, yellow, red, sometimes green apple-sized things growing on or fallen under the oaks? These galls, also called oak apple galls, are caused by Cynipid gall wasp larvae that create the enlarged, swollen plant tissue. The expert consensus seems to be that this Oregon white oak gall wasp species is benign, another lifestyle-dependent species.

Oregon white oak is resilient, despite Tent caterpillars, stem and branch cankers, powdery mildew, anthracnose, and chronic, slow mortality from Armillaria root disease (that’s already in Rogue Valley soils).

So far, Quercus garryana is resistant to Sudden Oak Death (SOD).

The Mediterranean Oak Borer (Xyleborus monographus), detected in California and in Oregon in 2018, targets many types of oak, including Oregon white oak. Harrington notes that “it’s a borer, but larvae eat fungi the adults bring with them that causes a wilting disease which can kill branches and eventually whole trees.” Clues include a tiny bark entrance hole and pale boring dust at the tree base.

References

Nolan, M. P., and J. M. Azerrad. 2024. Management recommendations for Washington’s priority habitats: Best management practices for mitigating impacts to Oregon white oak priority habitat. Washington Department of Fish and Wildlife, Olympia, Washington. https://wdfw.wa.gov/publications/02465

Doug Tallamy, YouTube, “Bringing Back the Natives Garden Tour

Margaret Roach, New York Times garden columnist, interviews Doug Tallamy on her awaytogarden.com blog. He lays out oak acorn “mast year” theories. https://awaytogarden.com/oaks-the-most-powerful-plant-of-all-with-doug-tallamy/

A Landowner’s Guide for Restoring and Managing Oregon White Oak Habitats,” by David Vesely and Gabe Tucker, 2004, Bureau of Land Management and others.

Klamath Bird Observatory and Lomakatsi Restoration Project. 2023. Restoring oak habitats in southwest Oregon and northern California: a guide for private landowners. Version 3.0. Rep. No. KBO-2023-0002. Klamath Bird Observatory, Ashland, OR.

Oregon Conservation Strategy for Oak Woodlands. Official analysis and current policy strategy.

“Biology and Management of Oregon White Oak,” Lecture, Connie Harrington, Clackamas Tree School, Oregon City, 3/23/24. Similar to Feb. 2021 video. https://extension.oregonstate.edu/video/biology-management-oregon-white-oak

Devine, Warren D.; Harrington, Constance A. 2010.

https://www.fs.usda.gov/pnw/pubs/pnw_gtr804.pdf

Harrington, Constance A.; Devine, Warren D. 2006. A practical guide to oak release. Gen. Tech. Rep. PNW-GTR-666. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 24 p

Swiecki, Tedmund J.; Bernhardt, Elizabeth. 2006. A field guide to insects and diseases of California oaks. Gen. Tech Rep. PSW-GTR-197. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. 151 p.

Garry oaks, also called Oregon white oaks, enjoy protected status,” The News Tribune, 9/9/2017

Photos by Maxine Cass

 

The Mistress of Master Gardener Propagation: Peggy Corum

By Beet 2024 12 December

 

I first submitted this tribute to Peggy Corum for publication in the Garden Beet in May of 2020.  Peggy passed away this past spring, 2024.

 

“I was born (89 years ago) of farming Nebraskans in a small town, at a wide place in the road, in a corner of Missouri.” Flags were always waving on Peggy Corum’s birthday, and it was years before she knew that the date – Nov. 11 – was Armistice Day (later Veteran’s Day).

“Everyone in my family was plant orientated,” she declares. “I pestered the little old lady next door, so she gave 4-year-old-me butterbean seeds. I planted them and that’s how I probably helped feed my family during the Depression.”

When she was 7, Peggy’s mom told her dad, “In Oregon, the cherries are so big, they look like plums!” and they moved west.  Our Master Gardener propagator to be grew up in Portland, attended a secretarial high school, and laughs when she remembers retiring three times – as office secretary for Medford’s Construction and Laborers Union, from her husband’s claims adjustment office, and as a propagator at Rogue Valley Roses. She lived for a few years with her husband in Germany and visited China to see rhododendrons.

Peggy learned propagation while she lived in Washington State from an expert rhododendron mentor who believed, “Anyone willing to put in work should have a connection to the best (plant material) there is,” and taught plant genetics and DNA long before those subjects were common knowledge. She learned about greenhouses and the less costly propagation tents later used in Peggy’s Propagation Garden. She became a Master Gardener in 1989, and soon was sharing what she had learned from the Pacific Rhododendron Society in a new Extension-based Grandma’s and Grandpa’s Garden.

Peggy always enjoyed visiting with friends while propagating and gardening.  She worked on the Garden Beet. Over the years, Peggy taught propagation to new Master Gardener classes, spoke at the Spring Garden Fair, held classes at Winter Dreams/Summer Gardens, gave community education class talks and was on the Master Gardener Speaker Bureau roster. “I’ve always worked in the elements.”

“Gardening is my reason for getting up in the morning,” Peggy said. Her favorite flower changes with the season: “I love most all of the plant world – but not poison oak!” Peggy smiles and admits, “I have a love affair with seeds; I can’t keep my hands off them. It’s so interesting when they ‘hatch’.”  Peggy, who lived in Ruch, has 4 children, 7 grandchildren, and 13 great-grandkids. When she’s not out in the elements, she knits, crochets, reads, and, “I still love to bake – cakes, cookies and pies.” Peggy Corum, The mistress of Master Gardener Propagation.

 

Willow Water: Mother Nature’s Rooting Hormone

By Beet 2024 12 December

A willow, the genus Salix, is a powerhouse of productivity for gardeners. For the propagation of cuttings, it’s a natural alternative to powdered or liquid rooting hormones. With 350 Salix species worldwide, tree to shrub-size, a willow is easy to find for making your own rooting hormone.  And willow water is inexpensive.

How is a willow able to provide a non-synthetic rooting hormone?  Many folks know willows as the plant that provided willow bark as a pain relief medicinal. In the 20th century, pharmaceutical manufacturers marketed a willow phytohormone, salicylic acid, as Aspirin. Willow also contains a powerful auxin, indole-3-acetic acid (IAA). This auxin hormone helps plants to grow cells, and pushes apical (bud) dominance and development. The University of California Botanical Garden notes that IAA stimulates root growth by reprogramming cells in the stem (of a cutting) to grow roots.

Making Willow Water

What gardener doesn’t want an easy task? (I recommend using protective gloves as you’ll be handling plant material with hormones.)

  • Gather 10-15 approximately pencil size-diameter, 12–18-inch willow branches from any willow with green or yellow bark (younger  growth). I prune these from branches above or from suckers at the base and make a diagonal pruning cut. Consider rinsing the willows to remove pollen, dust or wildfire residue.
  • Strip all leaves.
  • Cut branches into 1-inch pieces.
  • Place 1-inch willow twigs into a clean glass jar. 
  • Fill with unchlorinated and clean water. Bottled spring water is an option.

There are two methods:

  • Pour boiling water over the twigs and let stand, covered, for about 24 hours. OR
  • Pour water over the twigs and let stand, covered, for about 48-72 hours.
  • When time is up, strain the twigs and discard the pieces to the garden or compost.
  • The willow water is now ready. Cover and use within 60 days from preparation.
  • Label your willow water jar with “Willow Water,” date produced, date to use by (60 days), and any other details such as cold water, boiling water, willow species, etc.

 

Using Willow Water for Cutting Propagation

Pour a small amount, 0.5–1 inch, of prepared willow water into a jar, then place prepared cutting bottoms to soak in the willow water for several hours or more. As with synthetic rooting hormones, the cutting bases don’t need endless time to draw up those hormones. Extra willow water after finishing the cuttings’ soak can be tossed into the garden.

Willow facts

Most species like water and are well-adapted to wetlands, rivers and stream banks. In nature, willows are renowned for large root systems, chock full of small to huge roots. Don’t place willow plantings near building foundations, sidewalks or other areas where safety could be threatened.

Salix species are vigorous growers. Riparian restoration projects often hammer willow stakes in place to have new trees grow very quickly. A willow replaces pruned material quickly, so pruning a small amount of willow branches does no harm.

There’s an additional benefit if planting a new willow: The National Wildlife Federation lists it as a keystone species shrub for our two regions, Mediterranean CA- Ecoregion 11 (the Rogue Valley generally falls into this region by climate and soils) and Northwestern Forested Mountains – Ecoregion 6. A host plant for at least 256 species of butterfly caterpillars, willows also support 26 pollen-reliant specialist bee species.

Though any willow is perfect for making willow water, the Rogue Valley’s native species, Salix lasiandra (Shining Willow) and Salix scouleriana (Scouler’s Willow) are adapted to the region. For gardeners living in drier, less irrigated areas, Scouler’s willow is unusual, thriving away from moist areas.

References:

https://deepgreenpermaculture.com/2010/12/15/home-made-plant-rooting-hormone-willow-water/

 

© Maxine Cass for all photos