This species has a generally shrubby growth form to 12 meters in height; the champion specimen in Amador County has achieved a height of 17 meters. The crowns are dense and broadly conical. Bark is rough, furrowed and fibrous. Branchlets are comblike. Leaves exhibit a conspicuous, pitlike, abaxial gland that produces a drop of resin. Pollen cones are two to three mm long by two mm wide. Seed cones are globose, generally 1.5 to 2.5 cm in size, brown or gray, and not glaucous. The light to medium brown seeds are two to five mm long, and occasionally appear slightly glaucous. Among North America's true Cypresses, the MacNab cypress alone manifests flattened branchlets lying all in one plane.
Regularity: Regularly occurring
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
3 Southern Pacific Border
4 Sierra Mountains
Occurrence in North America
of any of the California cypress [14,27]. Numerous scattered groves
occur in the inner North Coast Ranges, the Sierra Nevada foothills, and
the Cascade Range [14,24,27]. Over 30 groves occur in the following
counties: Sonoma, Napa, Yolo, Mendocino, Lake, Colusa, Tehama, Shasta,
Butte, Nevada, Yuba, and Amador .
MacNab cypress is a native, evergreen tree with a broad crown and
lacking a main trunk [10,24]. It grows from 9.9 to 33 feet (3-10 m)
tall . It is unique among North American cypress because of the
flat, sprayed arrangement of its branches [2,24]. Mature leaves are
generally about 0.06 inch (1.5 mm) long, although they can be up to 0.4
inch (10 mm) on vigorous shoots [8,24]. Ovulate cones are solitary, up
to 1.0 inch (25 mm) long. Staminate cones are 0.08 to 0.12 inch (2-3
mm) long [8,24]. The bark is furrowed and fibrous, 2.54 to 5.1 inches
(1-2 cm) thick, and not exfoliating . A well-defined taproot and
numerous laterals are formed the first year .
Habitat and Ecology
In many areas MacNab cypress is restricted to serpentine soils, but in
other locations it occurs on clay loam (up to 5.0 feet [1.5 m] deep),
silty loam, alluvial, granitic, and volcanic soils [13,16,27]. It is
found on dry slopes, exposed hillsides, and ridgetops [8,16,20]. It
occurs at elevations from 1,000 to 2,800 feet (300-850 m) on north- to
northeast-facing slopes [8,20].
Key Plant Community Associations
MacNab cypress is a component of the northern interior cypress forest.
This community is an open, fire-maintained, scrubby forest similar to
the knobcone pine (Pinus attenuata) forest. It is associated with
serpentine chaparral, and intergrades on less severe sites with upper
Sonoran mixed chaparral, montane chaparral, or knobcone pine forest
community types. On more mesic sites the northern interior cypress
forest intergrades with mixed evergreen forest or montane coniferous
forest . MacNab cypress is associated with redwood (Sequoia
sempervirens)-Douglas-fir (Pseudotsuga menziesii) forest and associated
North Coast forests in Mendocino County, California [6,26]. It is also
commonly associated with chaparral and pine-oak (Pinus-Quercus spp.)
woodland species [8,27]. The Magalia grove in Butte County is
surrounded by yellow pine forest (Pinus ponderosa and P. jeffreyi) .
MacNab cypress occurs sympatrically with Sargent cypress in Lake County,
Publications naming MacNab cypress as a community dominant are listed below.
Terrestrial natural communities of California 
Terrestrial vegetation of California 
Species not previously mentioned but commonly associated with MacNab
cypress include gray pine (Pinus sabiniana), sugar pine (P.
lambertiana), incense-cedar (Libocedrus decurrens), California scrub oak
(Quercus dumosa), leather oak (Q. durata), interior live oak (Q.
wislizenii), valley oak (Q. lobata), Sierra coffeeberry (Rhamnus rubra),
California coffeeberry (R. californica), yerba santa (Eriodictyon
californicum), chaparral pea (Pickeringia montana), golden-fleece
(Haplopappus arborescens), Garrya congdonii (interior silktassel),
California hop tree (Ptelea crenulata), chamise (Adenostoma
fasciculatum), wedgeleaf ceanothus (Ceanothus cuneatus), musk brush (C.
jepsonii), whiteleaf manzanita (Arctostaphylos viscida), creeping sage
(Salvia sonomensis), and styrax (Styrax officinalis var. californica)
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
229 Pacific Douglas-fir
233 Oregon white oak
244 Pacific ponderosa pine - Douglas-fir
245 Pacific ponderosa pine
247 Jeffrey pine
248 Knobcone pine
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
K005 Mixed conifer forest
K006 Redwood forest
K029 California mixed evergreen forest
K030 California oakwoods
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES21 Ponderosa pine
FRES28 Western hardwoods
FRES34 Chaparral - mountain shrub
Fire Management Considerations
Fires occurring too frequently in McNab cypress groves may destroy them,
as reproduction could be eliminated before it had a chance to produce
cones. Conversely, fire suppression could threaten the species.
Plant Response to Fire
Lake County, it occurs on recently burned areas with Sargent cypress
In Aukum, California, many decadent MacNab cypress were reported in
1948. The prevalence of "overmature and decadent" Macnab cypress trees
was attributed to the absence of fire, which was veiwed as unusual for
this species. A few miles south, in Hooker Canyon, Sonoma County, a
chaparral atand of chamise and California scrub oak contained a few old
MacNab cypress, numerous burned MacNab cypress stumps, and many young
MacNab cypress trees .
Seedling regeneration is not as extensive for MacNab cypress as for
other cypress species, possible due to low germination rates .
Immediate Effect of Fire
to crown fires, which usually kill almost all trees in the stand .
At the Rancho Santa Ana Botanic Garden in southern California on October
8, 1943, a severe fire killed all but three MacNab cypress trees .
Cones of the California cypress open as the resin melts and boils.
Rapid charring of the thick cone scales extinguishes the flames, leaving
seeds unburned .
Tree without adventitious-bud root crown
Crown residual colonizer (on-site, initial community)
Initial-offsite colonizer (off-site, initial community)
MacNab cypress is a fire-adapted, fire-dependent species. Successful
cypress (Hesperocyparis spp.) reproduction is generally restricted to burned
sites . The serotinous cones persist on the trees for years .
Cone opening is erratic, slow, and almost negligible except when cones
are exposed to extreme heat; then it is rapid and uniform . When
opened by the heat of a fire, the seeds fall on exposed mineral soil
[14,24]. Most seed falls in the first few months following fire .
Fires that occur in late summer and fall and are followed by winter
rains ensure seed dissemination on bare mineral substrates . No
information was available on fire-free intervals for communities
dominated by MacNab cypress. However, Tecate cypress (Hesperocyparis
forbesii), a cypress found in southern California,
has an average interval between fires of 25 years, ranging from 15 to 63
years . Cypress trees of southern California generally reach
cone-bearing age before another fire occurs .
Site requirements for cypress seedlings are typical of those for pioneer
conifers. Seedlings are shade intolerant and survive best in full
sunlight on bare mineral soil . Perhaps due to its shorter, bushier
habit, MacNab cypress is found on more exposed sites than Sargent
cypress where the two species occur together .
MacNab cypress reproduces exclusively from seed. Cone production is
abundant. Staminate cones are produced on trees that are 6 to 7 years
old . Ovulate cones are produced on trees that are 14 years of age
or older. The cones require 2 years to mature . They contain from
75 to 105 seeds each [10,24]. The cones are closed; they persist on the
tree until opened by the heat of a fire or from desiccation due to age
[10,27]. Seeds are shed gradually over several months after the cones
are opened . Detached cones will open, but they rarely result in
seedling establishment, usually due to the lack of a suitable seedbed
. Seed dispersal is primarily by wind and rain .
MacNab cypress germination rates are extremely low, less than 5 percent
. Seeds require bare mineral soil for germination and
establishment. Seedling mortality is greater on shaded sites with
abundant litter because of damping-off fungi [2,27]. Seedlings are
sensitive to excessive moisture .
Growth Form (according to Raunkiær Life-form classification)
Life History and Behavior
Molecular Biology and Genetics
Barcode data: Hesperocyparis macnabiana
Statistics of barcoding coverage: Hesperocyparis macnabiana
Public Records: 6
Specimens with Barcodes: 6
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N4 - Apparently Secure
NatureServe Conservation Status
Rounded Global Status Rank: G4 - Apparently Secure
Grazing and trampling by livestock are detrimental to cypress seedlings .
MacNab cypress is unsuitable for use in windbreaks or hedges near the
coast or in areas that are waterlogged, because waterlogged soils may
result in dwarfed trees [24,27].
Seedlings are susceptible to damping-off fungi . MacNab cypress is
moderately susceptible to coryneum canker (Coryneum cardinale), which
can kill trees . It succumbs to various diseases when transplanted
from warm, dry interior locations to the cool, moist atmosphere of the
MacNab cypress is restricted to serpentine soils in many locations.
Using cypress wood to fuel the furnaces used to extract mercury from
sepentine soils has reduced California's cypress forests .
Relevance to Humans and Ecosystems
Importance to Livestock and Wildlife
undesirable forage for livestock, although young plants are browsed
Wood Products Value
MacNab cypress has soft, close-grained wood . Cypress (Hesperocyparis
spp.) wood is generally durable and stable. It is suitable for a wide
range of exterior uses including joinery, shingles, and boats. Possible
interior uses include moulding and panelling . Cypress shelterbelts
provide good fuel. Most cypress species develop a large proportion of
heartwood, which splits well, dries quickly, and is clean-burning.
Cypress wood is moderately fast burning because of its medium density.
As cypress woods are prone to sparking, they are recommended only for
enclosed fires .
Cupressus macnabiana (MacNab Cypress or Shasta Cypress) is a species of cypress in western North America.(A. Farjon. 2005)
It is endemic to northern California. Cupressus macnabiana is one of the most widely distributed of all the native California cypresses, found growing in chaparral, oak woodlands, and coniferous woodlands habitats along the inner northern California Coast Ranges and the foothills of the northern Sierra Nevada. MacNab cypress is often associated with ultramafic soils.(C. Michael Hogan. 2010)
Cupressus macnabiana is an evergreen shrub or small tree, 3–12 metres (9.8–39.4 ft) (rarely to 17 metres (56 ft)) tall, with a spreading crown that is often broader than it is tall. The foliage is produced in dense, short flat sprays (unlike most other California cypresses, which do not have flattened sprays), bright glaucous gray-green in color, with a strong spicy-resinous scent. The leaves are scale-like, 1-2 mm long with an acute apex, and a conspicuous white resin gland on the center of the leaf. Young seedlings produce needle-like leaves up to 10 mm long in their first year.
The seed cones are oblong-ovoid to cuboid, 15-25 mm long and 13-20 mm broad, with six (rarely four or eight) scales, each scale bearing a prominent umbo; they are strongly serotinous, not opening to release the seeds until the parent tree is killed by wildfire. This enables heavy seed release to colonize the bare, fire-cleared ground. The pollen cones are 3-4 mm long, and release their pollen in the fall.
- Conifer Specialist Group (1998). Cupressus macnabiana. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 December 2006.
- A. Farjon. 2005. A Monograph of Cupressaceae and Sciadopityaceae. Royal Botanic Gardens, Kew. ISBN 1-84246-068-4.
- C. Michael Hogan. 2010. Leather Oak, Quercus durata. Encyclopedia of Earth. National Council for Science and Environment. Wash.DC
- Stuart, J. D.; J. O. Sawyer (2001). Trees and Shrubs of California. University of California Press. ISBN 0-520-22110-9.
- Wolf, C. B. & Wagener, W. E. (1948). The New World cypresses. El Aliso 1: 195-205.
Names and Taxonomy
Cupressus macnabiana Murr. [14,18,24,28]
Neocupressus macnabiana (A. Murray bis) de Laub. 
macnabiana (A. Murray bis) Bartel [23,28]. There are no recognized infrataxa.
Natural hybridization between MacNab cypress and Sargent cypress
(H. sargentii) has been hypothesized, but evidence for it is