Palomar Gmelina
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White Teak Trees On Palomar College Campus
Lamiaceae (Mint Family): Gmelina arborea
© W.P. Armstrong 26 May 2022
Another interesting tree planted on the Palomar College campus is Gmelina arborea. The genus is pronounced "muh-LEE-nuh" with a silent G. It is known by several common names, including white teak and Malay beechwood. Most references place it in the mint family (Lamiaceae). Teak (Tectona grandis) is also placed in the mint family, although it was formerly in the closely-related verbena family (Verbenaceae). Gmelina is a widely distributed forest tree, including India, Thailand, Cambodia and southern China. The monophyletic mint family includes over 7,000 species, mostly shrubs and herbaceous species. This is one of the few arborescent species that I have ever photographed.

Image modified from Missouri Botanical Garden ...lamialesweb.htm

Some Economically Important Herbs In Mint Family

Lamiaceae: Mint Family (Formerly Labiatae)

Lavandula officinalis (L. angustifolia ssp. angustifolia) Lavender
Marrubium vulgare Horehound [Common in local hills near Palomar College.]
Melissa officinalis Balm or Lemon Balm [Leaves used as a flavoring for salads, soups and tea.]
Mentha piperita Peppermint
M. spicata Spearmint [Wild along San Luis Rey River Of San Diego County.]

Monarda didyma Bee Balm or Bergamot [Dried leaves and flowers used to make an aromatic tea; other species also used, including M. citriodora (lemon bee balm or lemon bergamot) and M. austromontana (Mexican bergamot); Note: The bergamot used in Earl Gray tea comes from Citrus bergamia (Rutaceae).]

Nepeta cataria Catnip
Origanum vulgare Oregano
O. majorana Marjoram
Rosmarinus officinalis Rosemary [Planted on campus.]
Salvia officinalis Sage [Also S. clevelandii in San Diego County.]
S. columbariae Chia [Common in local hills.]
Thymus vulgaris Thyme
Ocimum basilicum Basil
Satureja hortensis Savory

Mesona chinensis Jellywort [Plants are boiled in water and then cooled to make a gelatinous material called grass jelly, a refreshing beverage consumed in China.]

See The Delicious Cooking Herb Called Rosemary
See Photographs Of Sages (Salvia) In California
Lavender: Source Of Lavender Oil For Perfumes
Catnip: An Interesting Herb That Drives Cats Crazy
Lemon Balm: A Fragrant Herb Used As A Flavoring
Basil: A Fragrant Herb That Enhances Tomatoes
Horehound: An Herb Used To Make A Unique Candy
See Grass Jelly From Jellywort (Mesona chinensis)

Gmelina arborea near Industrial Technology Building

Flowers & Foliage of Gmelina arborea

Image modified from Plant Systematics: A Phylogenetic Approach, W.S. Judd, et al. (2008)

Comparison of Gmelina & Teak lumber.

Specific Gravity

Probably the best way to appreciate the relative hardness of different woods is the concept of "specific gravity," a numerical scale based on 1.0 for pure water. Without getting too mathematical, the specific gravity of a substance can easily be calculated by dividing its density (in grams per cubic centimeter) by the density of pure water (one gram per cubic centimeter). The brilliant Greek mathematician and inventor Archimedes discovered over 2,100 years ago that a body in water is buoyed up by a force equal to weight of the water displaced. Archimedes reportedly came upon this discovery in his bathtub, and ran out into the street without his clothing shouting "Eureka, I have found it." Since one gram of pure water occupies a volume of one cubic centimeter, anything having a specific gravity greater than 1.0 will sink in pure water. The principles of buoyancy and specific gravity are utilized in many ways, from scuba diving and chemistry to the hardness of dry, seasoned wood. Some of the heaviest hardwood trees and shrubs of the United States have specific gravities between 0.80 and 0.95; including shagbark hickory (Carya ovata), persimmon (Diospyros virginiana) and ironwood (Ostrya virginiana) of the eastern states, and canyon live oak (Quercus chrysolepis), Engelmann oak (Q. engelmannii), hollyleaf cherry (Prunus ilicifolia) and Santa Cruz Island ironwood (Lyonothamnus floribundus ssp. asplenifolius) of southern California. Although some of these trees are called ironwoods, their dense, dry wood will still float in water. Since the pure cell wall material (lignin and cellulose) of wood has a density of about 1.5 grams per cubic centimeter, even the world's heaviest hardwoods generally have specific gravities less than 1.5 due to tiny pores (lumens) within the cell walls. True ironwoods include trees and shrubs with dry, seasoned woods that actually sink in water, with specific gravities greater than 1.0. They include lignum vitae (Guaicum officinale, 1.37); quebracho (Schinopsis balansae, 1.28); pau d'arco (Tabebuia serratifolia, 1.20); knob-thorn (Acacia pallens, 1.19); desert ironwood (Olneya tesota, 1.15); and ebony (Diospyros ebenum, 1.12). To appreciate the weight of these hardwoods, compare them with tropical American balsa (Ochroma pyramidale), one of the softest and lightest woods with a specific gravity of only 0.17.

The relative density and weight (mass) of different woods
(or other substances) can be compared mathematically:

Comparison of Specific Gravities Of Woods

Note: Although not included in following table, the wood of Gmelina arborea is definitely not as dense as teak. There are variable specific gravities given in the literature, but certainly not in the heavy wood category of teak. The highest value I could find is 0.53 that puts it in the medium heavy category with mahogany.

   Native To San Diego County   
   E. U.S., California & Tropical   
Trees With Dry (Seasoned) Wood That Sinks In Water
Olneya tesota
(Desert Ironwood): 1.15
Guaiacum officinale)
(Lignum Vitae): 1.37
Cercocarpus betuloides
Mountain Mahogany: 1.10
Diospyros ebenum)
Ebony: 1.12
Very Heavy Wood
Prunus ilicifolia
Hollyleaf Cherry: 0.98
Diospyros virginiana
Persimmon: 0.83
Quercus engelmannii
Engelmann Oak: 0.94
Carya ovata
Shagbark Hickory: 0.83
Acacia greggii
Cat's Claw Acacia: 0.85
Ostrya virginiana
Eastern Ironwood: 0.80
Quercus chrysolepis
Canyon Live Oak: 0.85
Lyonothamnus floribundus
Catalina Ironwood: 0.80
Quercus agrifolia
Coast Live Oak: 0.83
Robinia pseudoacacia
Black Locust: 0.79
Prosopis glandulosa
Mesquite: 0.77
Maclura pomifera
Osage Orange: 0.77
Heavy Wood
Cornus nuttallii
Pacific Dogwood: 0.75
Carya illinoensis
Pecan: 0.72
Arbutus menziesii
Madrone: 0.71
Betula alleghaniensis
Yellow Birch: 0.69
Fraxinus velutina
Arizona Ash: 0.68
Quercus coccinea
Scarlet Oak: 0.67
Umbellularia californica
California Bay Tree: 0.65
Cercis canadensis
Redbud: 0.63
Quercus kelloggii
California Black Oak: 0.64
Tectona grandis
Teak: 0.63
Juglans californica
California Black Walnut: 0.63
Acer saccharum
Sugar Maple: 0.63
Medium Heavy Wood
Chilopsis linearis
Desert Willow: 0.59
Liquidambar styraciflua
Sweet Gum: 0.59
Cercidium floridum
Palo Verde: 0.55
Prunus serotina
Black Cherry: 0.56
Psorothamnus spinosus
Smoke Tree: 0.55
Acer saccharinum
Silver Maple: 0.53
Celtis reticulata
Western Hackberry: 0.53
Swietenia macrophylla
Honduras Mahogany: 0.51
Acer macrophyllum
Big-Leaf Maple: 0.50
Magnolia grandiflora
Southern Magnolia: 0.50
Soft Wood
Pinus ponderosa
Ponderosa Pine: 0.46
Sequoia sempervirens
Coast Redwood: 0.40
Calocedrus decurrens
Incense Cedar: 0.40
Picea engelmannii
Engelmann Spruce: 0.35
Pinus lambertiana
Sugar Pine: 0.36
Quercus suber
Cork Oak Bark: 0.24
Abies concolor
White Fir: 0.36
Ochroma pyramidale
Balsa: 0.17

Table 1. Comparison of some of the native woods in San Diego County, California with woods from other areas, including California, the eastern United States and tropical regions. Note: Angiosperm woods are often classified botanically as "hardwoods," while gymnosperms are called "softwoods." Although balsa is very soft and light, it is often placed in the hardwood category because it is an angiosperm.

Many Of The Species In Above Chart Are On The Palomar College Campus

RBC: Rancho Bernardo Campus; FEC: Fallbrook Campus; SM: San Marcos Main Campus; RS:Receiving Warehouse; MD: American Indian Studies; NS: Natural Science Bldg; J: Old Facilities Bldg; M: Men's Locker Room: O: Athletics Dance Studio; MC: Math Learning Center; SSC: Admissions/Registration

Trees With Dry (Seasoned) Wood That Sinks In Water

Olneya tesota = Baseball Field

Very Heavy Wood

Cercocarpus betuloides = NS California Native Garden, Arboretum, Baseball Field
Guaiacum officinale =Soccer Field
Prunus ilicifolia = J Building, Arboretum
Quercus engelmannii = NS California Native Garden, RBC and FEC
Acacia greggii = M & O Building
Quercus chrysolepis = M & O Building
Quercus agrifolia = All Over SM Campus, RBC and FEC
Prosopis glandulosa = Tennis courts, RBC
Lyonothamnus floribundus = Arboretum, RBC
Robinia pseudoacacia = Arboretum

Heavy Wood

Umbellularia californica = NS, O Building
Quercus kelloggii = NS California Native Garden, RBC
Juglans californica = RBC
Quercus coccinea = Possibly At Soccer Field. Need to confirm
Cercis canadensis = RS, MD, Soccer Field & RBC
Tectona grandis = Seed in Seed Bank; To Be Planted This Year (2022)

Medium Heavy Wood

Chilopsis linearis = All Campuses, Except Escondido Center
Cercidium floridum = MC Building, Tennis Courts, Cactus Garden, M & O and RBC
Liquidambar styraciflua = All Over The San Marcos Campus
Magnolia grandiflora = All Over The San Marcos Campus
Swietenia mahagoni = T Building (Industrial Arts)

Soft Wood

Calocedrus decurrens = Arboretum
Sequoia sempervirens = Bookstore, HS Building, Arboretum
Cork Oak Bark (Quercus suber) = SSC, North African/Arabian Peninsula Garden
Balsa (Ochroma pyramidale) = In Nursery, To Be Planted Out This Year (2022)

  See Wayne's Word Article About Hardwoods  

In Case You Are Wondering, The Commonly Cultivated Lantana
Belongs To The Closely Related Verbena Family (Verbenaceae)

San Diego Thornmint (Acanthomintha ilicifolia): Rarest Native Species In Mint Family
In Vicinity Of Palomar College. Sadly, Most Populations Destroyed By Developers

San Diego Thornmint
(Acanthomintha ilicifolia)

The rare & endangered San Diego thornmint (Acanthomintha ilicifolia) is native to clay lenses on the north slopes of Emerald Heights in the City of Escondido. Most of the population was extirpated during construction of large housing tract. Thornmint is an unusual member of the mint family (Lamiaceae) because it produces conspicuous spines on the floral bracts. Many years ago I discovered another small population in a vernal pool field near Palomar College. In fact, other endangered plant species occur on this property with an uncertain future.

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