Arboretum Newsletter 12

The True Cypress: Trees That Truly Qualify As Cypress

by W.P. Armstrong

In 1966 I wrote a Master’s Thesis entitled Ecological and Taxonomic Relationships of Cupressus in Southern California under the direction of Dr. R.J. Vogl, California State University, Los Angeles. Much of my thesis was published in chapter 9 of Terrestrial Vegetation of California, edited by M.J. Barbour and J. Major, University of California, Davis. California is a remarkable state botanically speaking because we have 10 species of cypress. True cypress belong to the genus Cupressus in the cypress family (Cupressaceae), along with junipers (Juniperus), false cypress (Chamaecyparis), incense cedar (Calocedrus), arborvitae (Thuja), Alaska cedar (Xanthocyparis), and the Australian cypress pine (Callitris). All these genera represent separate branches (clades) in computer-generated phylogenetic trees. A number of genera formerly assigned to the taxodium family (Taxodiaceae) have been merged into the cypress family, including redwood (Sequoia), giant sequoia (Sequoiadendron), dawn redwood (Metasequoia), and bald cypress (Taxodium). The principle exception is the genus Sciadopitys (Japanase umbella pine), which was found to be completely unlike the Cupressaceae, and is now placed in the monotypic family Sciadopityaceae. Modern taxonomists consider DNA sequencing to be more reliable for the differentiation between families. All these changes drive old botanists like myself crazy!

The modern classification of true cypress (Cupressus) is especially fascinating if you enjoy plant taxonomy. In October 1999, a new cypress species was discovered in northern Vietnam. It was named Xanthocyparis vietnamensis. [The name Cupressus vietnamensis also appears in some garden references.] Surprisingly enough, its closest relative was found to be the Alaska cedar (formerly Chamaecyparis nootkatensis syn. Cupressus nootkatensis), separated by thousands of miles and on opposite sides of the Pacific Ocean. The two species were so similar that the authors combined them generically, and the Alaska cedar became Xanthocyparis nootkatensis. The Alaska cedar forms spontaneous, fertile hybrids with Cupressus species when these are grown together in botanical gardens. In fact the cultivated Leyland cypress (Cupressocyparis leylandii) is a hybrid between the Monterey cypress (Cupressus macrocarpa) and the Alaska cedar. Coastal populations of Monterey cypress are resistant to corneum canker; however, trees planted in the interior valleys are very susceptible to this fungal disease. It is interesting to note that the Leyland cypress has also acquired this fungal susceptibility from its cypress parent. Evidence from DNA and morphology indicates that the Alaska cedar and the Vietnam cypress are closely related to the New World species of Cupressus which are genetically distinct from the European and Asian Cupressus. So quess what! The cypress of California and Mexico are now in a new genus Hesperocyparis.

Figure 3. Alaska cedar (Xanthocyparis nootkatensis) near Government Camp, Oregon.

The Jepson Flora of California (2nd Edition) lists 10 species of Hesperocyparis (formerly Cupressus), although some species have been reduced to varieties or subspecies by various authors. According to some botanists, disjunct species of cypress in California and Arizona have not been isolated long enough to warrant the status of a species. For example, species with glaucous, glandular foliage have been named subspecies of the Arizona cypress (H. arizonica). California cypress occur in isolated groves from the mountains of San Diego County to the Modoc Plateau of northern California. They also occur in Arizona, Baja California, and mainland Mexico. In my opinion, they are fairly distinct when you see them in their natural habitats, but in a botanical garden like the Palomar College Arboretum they are difficult to identify. The key to species in the Jepson Manual uses leaf and seed cone characteristics, persistent vs. exfoliating bark, and shape of crown. If all these characters are not available, good luck in determining the exact species unless you have access to a DNA sequencing lab! Phenotypic variability between different isolated groves of the same species may be due (in part) to genetic drift. These differences include slight variations in foliage and the general shape of seed cones. Differences attributed to genetic drift are analogous to racial differences in people, such as different blood type percentages and facial characteristics.

Figure1. Seed cones from cypress in California, Arizona and outside the U.S.

A - N: New World Cypress (Hesperocyparis) formerly placed in the genus Cupressus: A. Tecate cypress (Hesperocyparis forbesii), B. Sargent cypress (H. sargentii), C. Piute cypress (H. nevadensis), D. Cuyamaca cypress (H. stephensonii), E. Santa Cruz cypress (H. abramsiana, F. Monterey cypress (H. macrocarpa), G. Gowen cypress (H. goveniana), H. Mendocino cypress (H. pygmaea), I. Macnab cypress (H. macnabiana), J. Modoc cypress (H. bakeri), K. Smooth-bark Arizona cypress (H. glabra), L. Rough-bark Arizona cypress (H. arizonica), M. San Pedro Martir cypress (H. montana), N. Mexican cypress (H. lusitanica). O - R: Old World Cypress (Cupressus): O. Italian cypress (Cupressus sempervirens), P. Sahara cypress (C. dupreziana), Q. Kashmir cypress (C. cashmeriana), R. Mourning cypress (C. funebris). S: False Cypress (Chamaecyparis): S. Port Orford cedar (Chamaecyparis lawsoniana). T - U: Nootka Cypress (Xanthocyparis): T. Alaska cedar (Xanthocyparis nootkatensis), U. Leyland cypress Xanthocyparis x leylandii (Cupressocyparis leylandii in nursery trade).

Figure 2. Scale-like leaves of 5 species of Hersperocyparis in Palomar College Arboretum.

Figure5. Bark variation in California cypresses. A. Persistent, shreddy bark of Piute cypress (C. nevadensis). B. Exfoliating bark of Cuyamaca cypress (C. stephensonii).

Figure10. Two major types of foliage in cypress: A. Glaucous, very glandular (resinous) foliage and pollen cones of the Smooth-bark Arizona cypress (Hesperocyparis glabra) B. Bright green (nonresinous) foliage of the Tecate cypress (H. forbesii).

Millions of years ago, cypress woodlands containing one or more ancestral species once dominated vast areas of California. During the past 20 million years, as mountains were uplifted and the climate became increasingly more arid, most of these extensive cypress woodlands vanished from the landscape. In some areas, the cypress were probably unable to compete with more drought resistant, aggressive species, such as impenetrable chaparral shrubs and desert scrub. Although cypress are fire-adapted with serotinous seed cones that open after a fire, they are vulnerable if the fire interval occurs too frequently, before the trees are old enough to produce a sufficient cone crop. Chaparral shrubs quickly resprout after a fast-moving brush fire from well-established subterranean lignotubers. This may explain why some cypress groves occur in very rocky, sterile sites with poor soils where the chaparral shrubs can't compete as well.

One of these rock types with poor soils is called serpentine (serpentinite) , a greenish, shiny rock that is exposed throughout the Coast Ranges of central and northern California, and the Sierra Nevada foothills. It is low in plant nutrients and high in toxic metals. The name is derived from its resemblance to a snake skin. According to the California Geological Survey, serpentinite has been designated California's official state rock. Serpentinite is a magnesium silicate rock with a waxy luster and a shiny, marblelike appearance. It varies from cream white through all shades of green to black. Higher grade, deeply-colored serpentinites are used for animal carvings, particularly in Africa. Some polished serpentinites resemble jade in color and are used in pendants and rings. Serpentinite outcrops in California often contain many species of rare endemic plants adapted to this rock type, including several species of cypress.

Figure4. The distribution of some California cypress species coincide with serpentine outcrops. Other impoverished soil types include barren sandstone and metavolcanic rock. Cypress trees growing on rugged, rocky soils in the wild appear to be better anchored and able to withstand strong winds and rain, compared with top-heavy cultivated cypress in rain-soaked, loam soils.

The present-day world distribution of Old World cypress (Cupressus) includes Africa, Middle East and eastward along the Himalayas to China and North Vietnam. For thousands of years, Italian cypress (C. sempervirens) and mourning cypress (C. funebris) have been grown as ornamentals in the Mediterranean region and southern China. The beautiful, weeping Kashmir cypress (C. cashmeriana) has been cultivated around Buddhist Temples in Sikkim, Bhutan, Assam and nearby areas of Tibet and India. In Rome, the Church of Santa Sabina was built in the 5th century AD. The original door was made of Italian cypress with intricate carvings illustrating scenes from the Old and New Testaments. Whether or not cypress wood was used in the construction of Noah's Arc (Genesis 6:14) has been debated by biblical scholars for centuries. Italian cypress grew abundantly in the Middle East, and the seasoned timbers were very durable.

The cypress are a complex genus of cone-bearing trees that still challenge botanists. Based primarily on leaf characteristics, where they were purchased, and Grounds Supervisor Tony Rangel, I am reasonably certain about 5 species of New World Hesperocyparis in the Palomar College Arboretum: Tecate cypress (H. forbesii), smooth-bark Arizona cypress (C. glabra), Gowen cypress (H. goveniana), Monterey cypress (H. macrocarpa), and San Pedro Martir cypress (H. montana) of Baja California. We also have two Old World cypress: Italian cypress (Cupressus sempervirens) and weeping cypress (C. cashmeriana). But of all the true cypress my favorites are the California native species in remote, isolated groves throughout the state, appropriately called “arboreal islands.”

Figure6. Smooth-bark Arizona cypress (Cupressus glabra) along scenic Oak Creek Canyon, Arizona. The cypress have glaucous, glandular foliage and exfoliating bark.

Figure7. Monterey cypress (Hesperocyparis macrocarpa) at Point Lobos State Reserve on the coast of central California. This is probably the best known of all the 10 California species.

Who Pollinated The Rare Hawaiian Alula?

by W.P. Armstrong

Alula (Brighamia insignis) is a rare member of the lobelia family (Campanulaceae) endemic to steep sea cliffs on the island of Kauai. As of the year 2000, fewer than 100 of these remarkable plants grew in the wild. Alula can no longer produce seeds because its pollinator moth is now extinct. Luckily it responds well to hand pollination. Like the California condor, this unique species has been brought back from the brink of extinction through breeding programs at botanical gardens. A remarkable phenomenon occurred in the Polynesian Garden at Palomar College. An alula plant produced fruit capsules with viable seed and it was not hand pollinated by horticulturist extraordinaire & Arboretum president Tony Rangel! Its pollination mechanism remains a mystery--could it be another local long-tongued hawkmoth or a hummingbird?

Figure8. This alula (Brighamia insignis) produced fruit capsules with viable seed and it was not hand pollinated. Its pollination is a mystery--could it be another local long-tongue hawkmoth or a possibly a hummingbird?

The Frost Myth!

by W.P. Armstrong

The leaves of deciduous trees fall from the branches during the autumn months, thus preparing the trees for their winter dormancy period. As days grow shorter a special layer of cells develops at the base of the petiole. This “abscission layer” is controlled by hormones and neatly separates the leaf from its stem, thus causing it to fall with the slightest breeze. The fall coloring of deciduous trees may involve yellow carotenoid pigments (terpenes) as well as flavonoids. In red maple (Acer rubrum) colorless flavonols are converted into red anthocyanin as the chlorophyll breaks down. Contrary to some references, bright red autumn leaves can develop without a frost. The trees are genetically programmed to drop their leaves in the fall, and red anthocyanins replace chlorophylls in the leaves.

Figure#9. The leaves on this red maple (Acer rubrum) in the Palomar College Arboretum turned bright red without any frost in October-November 2017.

Calendar Of Events For 2018

For Room Numbers Please Refer To The On-Line Events Calendar:

  Basic Tree & Shrub Care   

Saturday, March 3, 2018 10:00 AM - 12:00 Noon

Tony Rangel will be covering many of the basics when it comes to tree and shrub care for the home gardener. Some of the topics will include planting, water management, soil types, fertilizer, trimming, planting in the right location and other useful information about plant care. The workshop will be more of an open forum type, so feel free to come with your questions about trees and shrub care. Bring a pen/pencil and a notebook to take notes. Near the end of the talk Tony will trim a few trees, bushes, and shrubs. These demonstrations will provide attendees with an opportunity to learn a few techniques that can help to keep their home gardens healthy and manicured.

Please wear comfortable closed-toed walking shoes and dress warmly. The temperature for March 3rd is forecasted to be around 58 degrees. Optional: Bring water, a snack, wear sunscreen, hat, sunglasses, etc.

Please RSVP Tony Rangel if you would like to attend this free workshop. Email: or call: (760) 744-1150 x3122. Free Parking in Parking Lot #12 for this event and time only. Meet outside the New Campus Police building next to the new Parking Structure in Lot #12.

  Tree Trimming Workshop  

Date To Be Announced Later: See On-Line Calendar Of Events

  How to Make Fake Lava Rocks  

Date To Be Announced Later: See On-Line Calendar Of Events

  Spring Clean-Up Day   

Saturday April 21, 2018 9:00 am – 3:00 pm

Meet at the Patron’s Pavilion in the Arboretum 1140 W. Mission Road, San Marcos, CA 92069. Free parking in Parking Lot #5 for this event day and time only.

Continental breakfast in the morning and lunch. Water will be provided throughout the day. Open to the public. Please bring your own gloves, garden tools, hat, sunscreen & sunglasses. Wear comfortable and protective shoes. (no flip-flops). Please mark your tools and personal items with your name and phone number.

RSVP Tony Rangel if you would like to join this Clean-Up Day event: or call (760) 744-1150 x3122

  Walking Tour at Rancho Bernardo Campus   

Date To Be Announced Later: See On-Line Calendar Of Events

NOTE TO FACULTY: You can receive Professional Development credit by taking our workshops, tours and lectures. Maximum of 2 hours of PD credit per semester. (PD Code #120).

Please sign-up with the Professional Development Office: or Call (760) 744-1150 x2250 for more information.