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Fall 2001 Newsletter


Saturday, September 15 Autumn Native Plant Sale
Wednesday, Oct 24 Attracting Birds To Your Garden Using Native Plants, Chapter Meeting

Riding thus in the late summer along the Sierra foothills, one is constantly impressed with climatic peculiarities of the region. With us in the East, plant life seems to continue till the first frost; but in the Sierra foot-hills, growth and active life culminate in June and early July, and then follow long months of warm stormless autumn wherein the hills grow slowly browner, and the whole air seems to ripen into a fascinating repose-a rich, dreamy quiet, with distance lost behind pearly hazes, with warm tranquil nights, dewless and silent. This period is wealthy in yellows and russets and browns, in great overhanging masses of oak, whose olive hue is warmed into umber depth.
    Clarence King, pioneering geologist who founded the U.S. Geological Service, wrote this in the 1860s.

Saturday, September 15
Sierra College Grass Valley
9 a.m. to 1 p.m.

There are many reasons why you should make time to come to the upcoming plant sale. Isn't there a space in your garden that has taken a beating this hot and dry summer and is really crying out for something new? Native plants are better adapted to endure the searing heat, seasonal drought, and drying winds that come with the territory of the Sierra Nevada foothills. And fall is the best time to plant perennials, shrubs and trees. The return of the rains in autumn coupled with the still-warm soil foster root growth and allow the new plantings to become established.

We'll be offering trees, shrubs, vines and perennials, including currants, native mock orange, sages, redbuds, flannel bush, sugar bush, and manzanita cultivars. Also for sale will be several native oak species and easy-to-grow hardy perennials such as penstemon, columbine, and monkeyflowers. There will be available many hard-to-find selections such as tiger lilies, wild iris, yarrows, and bigleaf maples. And for those who are deer-challenged, there will be drought-tolerant, deer-resistant lavenders, thyme and sage. We will have a wide selection of books on gardening, plant identification and hiking, as well as wildflower posters. This year we've introduced two new showy posters: California Native Oaks and California Grasses.

By participating in the plant sale, you will also be contributing to our goal of publishing a book on the wildflowers of Nevada and Placer counties, and allowing us to contribute to environmental and educational causes. All proceeds from the plant sales are used to further the goals of preserving California native flora. Come to think of it, you'll be also helping us to continue publishing this newsletter.

If you feel especially public spirited, we always can use help at the plant sale. And, of course, if you do volunteer you get a free one-gallon plant of your choice. So if you have a couple of hours in which you can help, we would greatly appreciate it. We need people who could cashier, help unload and label plants; help set up booths, displays and tables; help customers find their way around the sale; help people take plants to their cars; help pack up at the end of the sale. If you can help in any of these areas, please contact Karen Callahan at 272-5532 or e-mail her at

Hope to see you at the sale!


Wednesday, October 24, 7 p.m.
Nevada County Library Community Room
Nevada City.
"Attracting Birds to Your Garden Using Native Plants"
by Mark Chainey

In early summer, I attended a Nevada County Land Trust sponsored tour of Mark's and his wife Helen's garden and was astounded by the beauty and vitality of their grounds. Shaded, meandering wood-chipped paths led to a series of secret havens that were well provided with soothing water features, artfully-built nesting boxes and well-stocked feeders. The yard was teeming with bird life. Picturesque charred snags that had been installed throughout the garden not only provided nesting and perching places for birds, they contained imaginatively built water features and made wonderful garden sculptures. Mark's and Helen's garden attracts dozens of species of birds year-round. I enjoyed every minute I spent there. Mark and Helen have made great use of native plants to create this magnificent spot near Nevada City. Now you too will have the chance to share in some of Mark's expertise of using native plants to attract birds. (See his recommendations for wildlife-attracting plants in the next article.)

Mark is known for his great knowledge of birds and is a gifted photographer. Mark's slide show will illustrate his garden's special features that provide food, water and shelter for birds and other creatures. He will also show slides of some of the most useful and beautiful California natives for landscaping. Let's hope he also shows his baby bird photos, they are the best!

The library is located at 980 Helling Way, Nevada City. At the intersection of Hwy. 49 and 20 in Nevada City, turn west toward Downieville on Hwy 49. After approximately one mile, turn right at the Nevada County Government Office Buildings complex. Follow signs to Library.


by Mark Chainey

Moderate Climate Conditions

  1. Big-Leaf Maple (Acer macrophyllum)
    Deciduous tree 20-50 ft. high, smaller in the Sierras; broad crown, often multi-trunked. Deeply-lobed, bright green leaves up to one foot across, long wisteria-like clusters of tiny yellow flowers in April, buttery yellow fall color. Deer-resistant, a fine shade tree for moist or irrigated soils, foliage looks best with afternoon shade and regular watering. Handles heavy snow loads. Fast growing. Maples attract many beneficial insects and have highly-prized winged seeds, known as "samaras", both of which attract a variety of birds. Tender leaf buds eaten by grosbeaks, Cassin's and purple finches, pine siskins.
  2. Blackfruit Dogwood (Cornus sessilis)
    Deciduous shrub or small tree 9-12 ft. tall. Colorful all year: lime green winter stems; shining, rich green leaves are prominently veined, turn shades of yellow and pink in fall. Small creamy-white flowers in 1" clusters followed by decorative, shiny black, egg-shaped fruit at the branch tips. Easy-to-grow shrub or patio tree for part shade with irrigation. Provides important food for grouse, quail, woodpeckers and bluebirds.
  3. Western Bleeding Heart (Dicentra formosa)
    Native to moist woods along the Pacific Coast. Leafless flower stalks 8-18" high with clusters of pendulous pale or deep rose flowers on reddish stems April-June. Blue-green foliage. Variety 'Sweetheart', beautiful white flowers, light green leaves, blooms May-October. D.F. oregana, native of Siskiyou Mountains in southern Oregon and Northern California, grows about 8" high, has translucent blue green leaves, cream-colored flowers with rosy-tipped petals. Can help to establish a hummingbird population in your yard.
  4. Bearberry (Arctostaphylos uva-ursi) 'Woods Red"
    Attracts many birds that consume the colorful manzanita fruits. Species might include the fox sparrow, California and spotted towhees, cedar waxwing, grosbeaks, mountain and western bluebirds, scrub jay, Steller's jay, band-tailed pigeon, wrentit, mockingbird, California and mountain quails, and other sparrows.
  5. Western Chokecherry (Prunus virginiana var. demissa)
    Deciduous shrub or small tree 6-18 ft., usually smaller. Fragrant, large nodding conical clusters of tiny white flowers in spring followed by large showy clusters of red-purple berries. Exceptional fall color that ranges from orange-red to rose-red. Easy-to-grow and attracts at least 43 species of birds.
  6. Sierra Currant (Ribes nevadense)
    Hardy deciduous shrub 3-6 ft. high; upright, open branching. Showy, pendulous, 1-3" clusters of pink to reddish tubular flowers in late spring; blue-black summer berries; maple-like light green leaves, 1-3" wide, turn yellow in fall. Easy-to-grow, vigorous plant. Part shade or full sun with some water. Provides excellent cover for many song and game birds.
  7. Cascara Sagrada (Rhamnus purshiana)
    Deciduous shrub or small tree 9-30 ft. high. Magnolia-sized, shining, dark-green leaves with prominent veining are tufted at the ends of branches. In fall, leaves remain glossy and turn a shimmering butter-yellow. Small clusters of tiny white flowers in spring attract butterflies and beneficial insects, followed by large black berries displayed against the fall color. Fast-growing background shrub or screen. Sun or part shade, best with some irrigation.
  8. California Wild Rose (Rosa californica)
    Hardy, deciduous shrub 3-9 ft. high; erect and arching, thorny stems, forming broad thickets. Clusters of fragrant, pale to rose-pink, 11/2" single roses bloom May-September with a peak bloom in early summer. Vivid scarlet-orange rosehips on wine-red branches decorate the winter landscape. Rosehips attractive to many birds. Sun or light shade; tolerates heavy, wet soil or dry shade.
  9. Thimbleberry (Rubus parviflorus)
    Hardy, deciduous shrub, mostly under 3 ft. high; thornless, upright stems, spreading to form small thickets. Showy, single white roses 11/2" wide bloom May-July, followed by small, edible raspberries. Attractive maple-like leaves 3-12" wide turn yellow in fall. Beautiful bold textured ground cover for dry or moist shade. Part or full shade; tolerates drought. Attracts most woodland bird species that eat fruit.
  10. California Wild Grape (Vitis californica)
    Deciduous vine to 30 ft. high. In full sun, large maple-like leaves turn brilliant red in fall; in shade, clear yellow. Summer-fall clusters of purple grapes make excellent jelly or wine. Vigorous, easy to grow; can be pruned hard to keep smaller. Attracts mountain and western bluebirds, mockingbirds, wood ducks, green-winged teals, sparrows, towhees, some flycatchers, California and mountain quail, as well as numerous other birds.

Hot & Dry Climate Conditions

  1. McMinn's manzanita (Arctostaphylos densiflora 'Howard McMinn')
    Evergreen shrub 4-6 ft. high, 5-7 ft. wide; dense mounding. Compact foliage, mahogany-red stems, clusters of pink bell-shaped flowers. Neat and tidy; low in leaf litter. Probably the easiest-to-grow and most used manzanita.
  2. Western Serviceberry (Amelanchier alnifolia)
    Deciduous shrub or small tree 3-20 ft. high, usually under 8 ft. in the Sierras. Pure white, forsythia-like flowers in early spring, followed by 1/4-1/2" blue-purple fruits that drive birds wild. 1" blue-green leaves turns shades of purple, crimson, orange and yellow in fall. Tolerates heat, cold, drought and poor soil. A fine background shrub for sun or light shade. One of the best bird attractants: lures some of the most reclusive species, such as the spectacular pileated woodpecker, out into the open. Other species might include Townsend's solitaire, black phoebe, downy and other woodpeckers, chickadees, thrushes, western tanager, northern oriole, and northern mockingbird.
  3. Spice Bush (Calycanthus occidentalis)
    Deciduous shrub 4-12 ft. high, arching. Exotic mahogany-red flowers like small water lilies, long summer bloom. Lush, glossy, bright green, 2-6" long, pointed, oval leaves with a spicy, wine-like fragrance when crushed. Yellow fall color. Best with afternoon shade inland. Associated with small wooded streams, an excellent choice for woodland gardens. Great plant for insectivorous birds.
  4. Brown dogwood/smooth dogwood (Cornus glabata)
    Deciduous shrub or tree 4-12 ft. tall, usually smaller. Smaller, narrower lance-shaped leaves create a finer textured appearance than other dogwoods; good red to burgundy fall color. Thicket-forming, good for erosion control. Easy-to-grow shrub for sun or part shade with irrigation. Thrives in low-elevation gardens. Fall display of white berry-like fruit is very attractive to birds, including the western kingbird.
  5. Silver Bush Lupine (Lupinus albifrons)
    Semi-evergreen shrub 2-5 ft. high, rounded. Foot-long spikes of violet-blue, sweet pea-shaped flowers with yellow banner petals. Striking, silvery-silky, palmately compound leaves look good all year. Beautiful dry bank cover or accent for shrub border. Full sun, well-drained soil. Tolerates heat, nutrient-poor soil. Seed for ground-feeding birds, especially quail, and nectar for hummingbirds.
  6. Holly-leaf Cherry (Prunus ilicifolia)
    Evergreen shrub to 15 ft. or small tree to 30 ft.; compact, mounding crown. Polished deep green, leathery, broadly-oval, toothed leaves emerge bright apple-green. Showy elongated cluster of fragrant, tiny, white flowers at branch tips in late spring, followed by reddish-purple cherries. Excellent formal hedge; responds well to shearing. Tall screen or dark evergreen for the shrub border. Easy to grow, tolerates heat, drought and many soil types. California coast range species.
  7. Leather Oak (Quercus durata)
    Evergreen shrub 3-9 ft. high; compact, mounding. Leathery, convex, small leaves are densely set along the stems. Yellowish acorns in fall at the tips of branches. Full sun, tolerates heat, drought, poor soils, good for erosion control. Host plant to unique serpentine butterfly, Leather Oak Skipper. An interesting evergreen background shrub, never rangy. Ideal for small gardens. Produces acorns at a much younger age than most other oaks.
  8. Chaparral Flowering Currant (Ribes malvaceum)
    Semi-evergreen shrub 3-6 ft. high, many erect stems from base. Pale-pink, small tubular flowers, in pendant clusters 2-4" long, blooms winter to early spring. 1-3" clusters of pink to reddish tubular flowers in late spring. Blue-black summer berries. Maple-like, light green leaves, 1-3" wide, turn yellow in fall. Easy to grow and vigorous, a pretty flowering specimen, hedge, or bank cover. Part shade or full sun with some water.
  9. Mexican Elderberry (Sambucus mexicana)
    Deciduous multi-trunked shrub or small tree 6-24 ft. high, fountain-shaped. Light green leaves that go summer dormant in very dry soils. Flower clusters usually 2-8"wide, followed by blue-black berries that attract birds. Fast, easy-to-grow screen or background shrub for sun or shade, moist or dry soil.
  10. California fuschia (Epilobium canum)
    Perennial to 18", 2-4 ft. wide. Terminal clusters of glowing scarlet-red tubular flowers attract hummingbirds summer to fall. Small, lance-shaped, gray-green leaves combine well with flowers; evergreen in mild climates. A striking late-blooming border plant or small scale ground cover for well-drained soil. Tolerates, heat, drought, poor soil. Excellent choice for a hummingbird garden.


by Richard Hanes

Acting on a tip that the Sierra Primrose was in abundance on Red Mountain, Karen Callahan (she had the directions) and I (I had the high profile 4WD pickup) set off in late July to find it. Red Mountain is north of Cisco Grove.

Our progress was slow because the road was a washboard and we had to stop periodically to check the wildflowers and to photograph Gray's Lovage (Ligusticum grayi) and Alpine Knotweed (Polygonum phytolacceafolium). Past experiences taught us that we would never reach our destination if we kept stopping, so we put on the blinders and forged ahead toward Signal Peak.

The road to Signal Peak is not signed, but we made the correct choice. On our way we passed a pond and a group of 4-H young people waiting for the lunch truck. They had hiked up Red Mountain from their camp located at 6200 feet to the pond at 7200 feet. We wanted to explore the pond, but decided to return after the kids had gone. Karen and I had lunch on a windy ridge at 7400 feet; we had stopped just before the road started up the steep, rough ascent to Signal Peak. The view was fabulous, to the north was Fordyce Creek canyon and Old Man Mountain, to the east was a glimpse of Sterling Lake, to the south was Rattlesnake Creek canyon with a far view of the Sierra crest, and to the west was Signal Peak at over 7800 feet. There were just a few trees on this windswept ridge, Lodgepole Pine (Pinus contorta var. murrayana), Red Fir, (Abies magnifica), Western White Pine (Pinus monticola), and Western Juniper (Juniperus occidentalis). The shrubs were Huckleberry Oak (Quercus vaccinifolia) and Bittercherry (Prunus emarginata) with its bright red berries. The most obvious forb was Buckwheat; the one I photographed was Hoary Buckwheat (Eriogonum incanum). But no sign of the Sierra Primrose!

After lunch we returned to the pond. It is about 100 feet in diameter and about 1 to 2 feet deep. It contained a few plants of Pond Lily (Nuphar luteum), and an aquatic grass-like plant. The pool is surrounded by Inflated Sedge (Carex vesicaria), Eastwood's Willow (Salix eastwoodiae), Sedge (Carex sp.), Yampah (Perideridia sp.), Monkeyflower (Mimulus primuloides), Corn Lily (Veratrum californicum), Mountain Spiraea (Spiraea densiflora); drier slopes contain Huckleberry Oak with an overstory of Lodgepole Pine, Red Fir, and Western White Pine.

BUT WHAT ARE THOSE LITTLE CRITTERS SWIMMING NEAR THE EDGE???!!! They are blue, about 1 inch long, and they seem to swim with a wave-like motion. We decided they were not pollywogs, so I went to my library in the truck and consulted "Sierra Nevada Natural History". I took a guess and looked up Fairy Shrimp and they were/are!!! The only thing I knew about Fairy Shrimp was that they occur in vernal pools, so we quickly renamed the pond a vernal pool.

After returning home I notified Kathy Van Zuuk, Ecologist for the Nevada City Ranger District, Tahoe National Forest because many Fairy Shrimp are listed as threatened or endangered. Excitement ensued! After phone calls and e-mail messages, I finally located an expert willing to identify the critters, but I had to collect them and mail them to him.

So, back we went with an aquarium net on a long stick and bottles of rubbing alcohol. Our expert identified them as Streptocephalus sealii, which has no federal or state status. This did not dampen our excitement!

I have learned that Fairy Shrimp (Crustaceans) swim or glide upside down by means of beating movements that pass along their 11 pairs of legs in a wave-like motion. They feed on algae, bacteria, protozoa, rotifers, and bits of detritus. Their eggs (cysts) are capable of withstanding heat, cold, and prolonged dry periods. The cysts develop rapidly into adults and often disappear long before the vernal pools dry up. S. sealii has no common name and is common in the U.S., but information about their occurrence in California is very skimpy.

Additional excitement was created by our first siting of a Blue Grouse hen with 2 chicks in Lodgepole Pine thickets near a small meadow.

An exciting trip, both flora and fauna for a change!


Plans for Wildflower Preserve at Hell's Half Acre to be Submitted to City of Grass Valley

A development plan for the 330 acre Kenny Ranch property-a.k.a. Hell's Half Acre-site of some of Nevada County's most diverse, rare and spectacular spring wildflower displays, has been under preparation for the last year, and will be ready for submittal to the City of Grass Valley within the next six weeks, according to Brian Bisnett of Bisnett Design Associates, head planner for the project. Bisnett has been working closely with Carolyn Chainey-Davis to include 18 acres of prime lava-cap wildflower land in the project's open space areas, along with buffer vegetation zones to aid in protection of this unique resource. Additionally, over 90 acres of oak and pine woodland will be preserved as open space, and an additional 70 acres will be protected from development by the project's CC&Rs.

The development plan has substituted moderate cost work-force housing for the intense commercial and business park uses originally planned for the site, which should greatly assist in reducing impacts on the protected areas. A series of public meetings will be announced in September to present the proposed site plan to the project's neighbors and other interested parties. For additional information please call Brian Bisnett at 268-9733 or email at

(Eds. note: For those of you who live in Nevada County, you are undoubtedly aware of the continuing tempest surrounding Natural Heritage 2020 (NH2020). I'm afraid the very vocal opponents of NH2020 have taken the position that they don't want to be burdened with facts. They continue to disseminate misinformation, and howl loudly at every opportunity. The opponents would like to gut the Endangered Species Act. They would have you believe that NH2020 is a government Communist plot to confiscate land or at the very least raise all our taxes. But it is nothing of the sort. The article below explains just what NH2020 is trying to accomplish, and it is a very laudable mission. Future plans for Nevada County should be based on solid science, not baseless accusations and personal attacks. If we don't stand up for NH2020, who will? Please don't let the uninformed dominate the issue. If you have time, write a letter of support to your county supervisor or the Union.)


By Leigh Fitzpatrick, Sierra Business Council

NH 2020 is a program to identify and protect the natural resources that are the foundation of Nevada County's prosperity. Launched last year, NH 2020 carries out specific requirements in the county General Plan to study the county's natural resources and develop options to protect them. Altogether, NH 2020 has five important characteristics:

  • NH 2020 is modeled after similar programs around California and the US: Hundreds of communities nationwide are dealing with growth through collaborative processes to identify resources at risk and non-regulatory tools to protect them. NH 2020 is Nevada County's opportunity to get ahead of the curve on growth issues - in the same way neighboring Placer County did with the establishment of Placer Legacy, a successful effort that brought together everyone from developers, environmentalists, and farmers to create a plan for protecting the county's landscapes.
  • NH 2020 is science-based: The program has a top-notch science advisory committee, which is gathering information on important natural resources and verifying that data through limited field surveys on public land and private land by invitation only.
  • NH 2020 relies on citizen leadership and public participation: NH 2020 takes the discussion about growth out of the back room and puts it before the public. There have already been five public input forums that drew more than 900 residents.

NH 2020 also has the benefit of great citizen leadership: three working groups focused on agriculture, recreation, and forests, and a 14 member Community Advisory Committee (CAC) made up of leaders from every part of the county and all walks of life. Everyone's viewpoint is represented on these groups.

  • NH 2020 is not focused on regulation and will rely on voluntary participants: The key to NH 2020 is developing a program to create voluntary mechanisms to protect important habitat and working landscapes.
  • NH 2020 respects private property rights: The charge has been made that NH 2020 will violate property owners' rights. That is nonsense. From the beginning, the Board of Supervisors has been explicit that the objective is a voluntary program to protect the county's natural resources. The Board itself adopted a special six point "property owners' bill of rights" which guarantees NH 2020 will not affect property owners' rights. There will be:
  • no use of eminent domain;
  • no trespassing on private property;
  • no new taxes unless approved by the voters of Nevada County.

Not only does NH 2020 respect property rights, it expands property owners' options. The program can help farmers and ranchers generate new income to support their agricultural activities by selling or transferring their development rights - and not their land.


Longtime Tahoe National Forest Botanist, Kathy Van Zuuk, is now District Ecologist for the Nevada City Ranger District. Kathy is a dedicated professional and strong advocate for science and conservation.

The sad news, however, is that the position of Forest Botanist for the whole Forest was eliminated in 2001, supposedly to save money. The elimination of this position will drastically reduce attention to TNF's rare and sensitive plants and many other plant-related issues. The present lack of a specific Forest Botanist position will also make contacting TNF more difficult for the public when a forest-wide perspective and technical knowledge is needed. Letters from the public and CNPS members are needed to support a Forest Botanist position in 2002. Please write to Steven T. Eubanks, Forest Supervisor, Tahoe National Forest, 631 Coyote Street, Nevada City, CA, 95959.


Adapted from an article by Marcia Braga

The oaks of our native forests host some of the most ornamental and colorful galls to be found in North America, and give us an added dash of autumn color. They range from dull greens and browns to brighter colors of purple, pink, orange-yellow and red. They come in a variety of guises: little chalices standing erect upon a leaf surface, or spiny, sea urchins and even large, round wooden-like balls usually found on branches and tree trunks. They can be as small as a pinhead or as large as softball.

Just what are galls? These tumor-like sanctuaries harbor developing insect larvae. These strange and unusual swellings or deformities, which occur on or off leaves, branches, buds and even acorns, are triggered by the actions of fungi, mites, aphids, flies or wasps. Leaves are a favorite spot because they have a rapid growth rate and high nutritional content. Gall formation begins when an insect deposits its eggs into plant tissue, and accelerates when the emerging larvae secrete chemicals that cause the tree to wall off the invaded site. The result is a protected environment and a source of food for the developing insect.

Tiny wasps of the family Cynipidae are the most abundant gall inducers and produce the majority of galls that decorate California oaks. More than 200 species of cynipid wasps are associated with California's native oaks. Blue oaks exhibit the greatest diversity of galls. It is not unusual for sing specimen of blue oak to be decorated with the galls of 20 to 30 species of wasps.

Cynipid wasps are no larger than the head of a pin. The adult wasp lays its eggs in a leaf, stem or bud, and this triggers a response in the surrounding plant cells. The exaggerated differentiation and growth of the plant cells into gall structures is caused by compounds produced by the emerging wasp larvae. The larvae feed on the interior lining of the gall, which causes more nutrients to be delivered into the gall's chamber walls. This system provides not only a great food source but also a protective shelter from the elements until the adults emerge in the spring, and the cycle starts all over again. The galls, and the wasps that cause them, will not harm a healthy tree. Such a small amount of the plant's nutrients are diverted to the gall structure, it usually does not affect the health or vigor of the tree. The products of gall inducement by the insect are so specific that the identification of the organism responsible can often be made by recognition of the gall formation alone. Some cynipid wasps are so species-specific that they will seek out and utilize only one species of oak to host their eggs. As with all creatures in the web of life, gall organisms are susceptible to parasitic attack. Gall tissue as well as the resident larvae can become a food source for a vast array of other insects, mammals and birds. Galls have also been used as a natural resource base by humans for compounds such as inks, dyes, supplementary feed for livestock, antiseptics, astringents and preservatives used in edible oils. Young oak galls containing tannin were harvested by the Lake Miwok Indians and used to produce an ink for tatooing. For more information, an excellent resource is " Plant Galls of the California Region" by Ronald A. Russo.


I suspect that I don't have to remind anyone of the lamentably meager rains of the past season. Already in only early August, the ground lies cracked, the native grasses withered and dried-out blue oak leaves are fluttering to the ground. Many of the blue oaks, the signature tree of the blue-oak woodland that makes up so much of the populated areas of Nevada and Placer counties, look a tad tattered and weary this year. However, the premature shedding of leaves is merely a strategy for weathering the current dry year and an exquisite adaptation to their environment.

Blue oaks have evolved to withstand these disappointing years of little rain and high temperatures. According to the "Oaks of California" by Bruce Pavlik, Pamela Muick, Sharon Johnson and Marjorie Popper, while other oaks are resistant to drought, few of them combine all the mechanisms of conservation, tolerance and resiliency that are present in the blue oak. The following information on the variety of characteristics of blue oaks that prepare them for long seasons of no rain is derived from the "Oaks of California".

The leaves of blue oak are moisture conserving by their nature. They are covered on their upper surface by a waxy coating that gives the tree its characteristic bluish cast. Also the canopy of leaves remains proportionately smaller in blue oaks than in other less drought-tolerant species.

When water from the soil becomes very scarce, the blue oak exhibits a remarkable array of drought-coping behaviors. Leaves become reinforced with cellulose and lignin (the chemical component of wood) to withstand the physical stresses imposed by the progressive dehydration. Photosynthetic cells adjust their internal salt content so that wilting is prevented even if their leaves lose up to 30% of their water to the bone-dry atmosphere. This ability surpasses that of some desert trees, such as the mesquite and ironwood.

The dry summer sky steadily drains water from the soil through evaporation from the leaves. Vessels that conduct water in stems and roots must be able to withstand great internal tensions, just as a drinking straw must withstand the vacuum created by sucking a thick drink. As summer drought progresses, newly formed oak vessels become progressively thicker, harder and more compact, decreasing the likelihood of collapse as roots withdraw the last droplets of soil-bound moisture.

If water finally becomes too scare, blue oaks simply drop their leaves, a condition known as drought deciduous. Drought-deciduous leaves are a common feature of chaparral and desert shrubs, but rare among oaks and trees in general. Yet in extremely hot and dry years, blue oaks resort to such dormancy. The may look skeletal, but they are merely dormant, and they continue to fill their acorns with previously stored food. Most of the trees do not resume growth with arrival of fall rains, but wait until spring to produce a new crop of leaves. This ability to endure allows blue oaks to dominate nearly half of all oak-covered lands in California. Aren't we lucky to have them grace our hillsides?


    the web site for Las Pilitas Nursery. 2000 pages of information about California native plants, including revegetation and bird & butterfly gardening!
    a Newsletter of Natural History Trivia, fun articles on botany with titles like "Amazing Fungus Flowers".
    Visit some of the wild & scenic areas of Placer Co. via Russell Towle's web pages. Hiking trails, geology, history & a wildflower photo gallery of the North Fork of the American River.

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Last updated
Oct 2 2001