Torrey Pine

Torrey Pines (Pinus torreyana) are the rarest pine in North America. Native trees today are found only on one spot on Santa Rosa Island  and on the sandy bluffs of northern San Diego, where many are protected in the Torrey Pines State Reserve (TPSR) and Extension. The scattered trees growing in the  San Elijo Lagoon Reserve have probably been planted by scrub jays, hiding pine nuts for a future meal.

Walking beneath a torrey pine on a foggy day is like passing through a tiny rain storm. The long, minutely-sculpted needles condense fog into droplets that fall to the ground, providing additional moisture during the dry summer months.

Description ^{2,5,24,32,290}

Torrey pine is an evergreen tree with an extensive root system. When grown under the influence of coastal winds, it is may be less than 25 feet (8.5 m) high, picturesque with bent and twisted branches. In protected areas, it may exceed twice that height, with a straight trunk and broad, rounded canopy. The gray-green needles are eight to 12 inches long, in bunches of five (occasionally four or three). In cross-section, each needle in a five-needle cluster is 1/5th of a circle; where they come together at the base they form a cylinder that is surrounded by a papery sheath. Needles live three years, turning brown and falling the autumn of year three.

The reproductive structures of pines and other conifers are called strobili. There are male and female strobili on the same tree; the female structures occur further out on the branches than the males. The female strobilus is a round, prickly ball, about 1/2 inch in diameter, bright red when young, fading to dull red, then green then brown as it develops into the cone. The male strobili resemble small catkins, producing abundant pollen that is wind distributed. Strobili are produced in January to February.¹

Mature cones are dark brown, rounded and up to 6 inches (16 cm) wide; they are larger and heavier than cones of most pines. Each scale of the cone is tipped with a stout, reflexed prickle. At the base of each scale, protected by the adjacent scale, are up to two large, smooth, brown or blackish seeds, 5/8 inch to almost one inch (1.6 – 2.5 cm) long. Cones mature in their third year. They are often retained on the tree and seeds are released slowly over ten years or more. Like other pines, each seed has a wing, but in the Torrey pine, this is small and papery and is easily detached from the seed – apparently useless for transport, which depends instead on birds (especially scrub jays) and small mammals.

Classification ^2,143,310

Torrey pines are Gymnosperms, a major group of higher plants separated from flowering plants by the lack of flowers. The female ovule develops on the surface of a cone scale. It is protected by the surrounding scales but is exposed to the air rather than being enclosed in an ovary. Gymnosperms are commonly known as conifers or evergreens and include, in addition to pines, trees such as spruces, firs, cedars, and redwoods.

Within the conifers, pines are distinguished by having needle-like leaves that occur in bundles of one to eight, each bundle wrapped at the base with a membranous sheath.

In California, there are 18 species of pines. Torrey pines can be recognized by having both five needles in a bundle and a sharp prickle on the end of each cone scale.

The mainland and Santa Rosa populations are considered to be different subspecies: ssp. torreyana and ssp. insularis, respectively.²

Ecology  

Any one who has visited TPSR early on a foggy day knows that each tree becomes a little rain cloud, sending water dripping to the ground (and the person) below. Plant ecologists generally agree that fog can be a significant source of water in some areas, especially during periods of little or no rainfall. This “fog drip” has been shown to be important in several environments ^{41,368, 369,370,371} including montane cloud forests and the coastal evergreen forests of northern California. In these habitats, fog drip may equal or exceed rainfall amounts.

In coastal southern California where annual rainfall is very limited, cloud shading and fog drip significantly reduce drought-stress in pines.^{368,369,372,373} Because fog here occurs primarily in the summer when rainfall is often absent, the effect of even a little fog drip on tree growth appears to be very important – possibly making the difference between survival and death in a very marginal habitat.

The needles of conifers appear to be especially well suited for fog capture,³⁷⁴ perhaps because larger leaves divert airflow around and past their surfaces while the flat or thin needles promote direct collision and capture.³⁷⁵ In a two-year science project a local school student, Brock Oury, while in 7th and 8th grades, designed a fog chamber with which to compare the fog drip of Torrey Pines with that of four other pines. The Torrey needles condensed the most water. Brock speculated that this was due to the larger size and number of needles in a bundle.³⁷⁶ In the second year, this project was extended and the needles of the five pines were examined microscopically.³⁷⁷ Needle surfaces are sculpted with many series of microscopic projections that define tiny channels running the length of the needle. The projections on the Torrey pine needle are both larger and more numerous than those of the other species and Brock speculated that these are the sites of fog condensation, where the tiny fog droplets are captured and merged into larger drops that move down the channels and off the needle to the ground (or person) below. Brock’s second-year project won first place at the State Science Fair in the category of Plant Biology.^378,379 Nice job, Brock.

Note: Earlier this year, 2017, another local student, Emily Tianshi won national recognition for her studies on the fog-capturing abilities of the Torrey pine ³⁸⁰ but so far we do not know the details of the project.

Human Uses  

The Kumeyaay ate the Torrey pine seeds (often called pine nuts) either raw or cooked. They were also ground and cooked as pinole or added to other dishes for flavoring. The nuts were collected in the fall; often the cones were roasted to release the nuts.¹⁶

Modern tribes use the long Torrey pine needles for structure in open coiled baskets.¹⁵

Torrey pines are often used as ornamentals in coastal and inland southern California, and even the Central Valley. ^5,24

Interesting Facts  

Most people know what a native plant is – or do they? The concept is clear, but it is often difficult to apply.

Technically, the term “native” (or “indigenous”) means that a species persists in an area, such as North America, or California, or San Elijo Ecological Reserve, without being brought there by man.^4,59 However we rarely know the circumstances under which a species first arrived, so scientists have established the rather arbitrary determination that plants that were in North America (or California, or San Elijo Lagoon Reserve) before the arrival of the Europeans are native to that area, while in the absence of more direct information, plants that arrived later are non-native. A useful definition that has many ambiguous applications.

By either definition, Torrey pines are native to California, but within the San Diego area, they are thought to be non-native outside of the small population in and near Torrey Pines State Reserve; outside TPSR it is assumed they were either planted by humans or introduced by birds or mammals from the trees planted by humans.

However, it is highly unlikely that birds and mammals recognize the boundaries of TPSR. Surely, jays and ground squirrels are constantly hiding the pine nuts in the canyons and parks outside reserve limits. Just suppose that one of those pine nuts made its way to San Elijo Lagoon Ecological Reserve and then sprouted. Perhaps it took several generations to cover the distance, each generation moving one canyon further north, but so long as transportation was provided only by bird or mammal power (human hands off!) that torrey pine would be native to the San Elijo Lagoon Reserve. Unlikely perhaps, but only the jays know for sure, and they probably don’t care.