The taxonomic boundary between Pinus ayacahuite Ehrenb. ex Schltdl. and Pinus strobiformis Engelm. has been interpreted differently among specialists in the taxonomy of pines. Some have tended to use a wider concept of P. ayacahuite and others a wider concept of P. strobiformis (to include P. ayacahuite var. veitchii for instance). The boundary is not clear and has traditionally been drawn based primarily on observed variation in the seed cones and the seeds. Genetically, it is likely that there is introgression between these two closely related species, but a geographical zone in which this possibly occurs has not been defined[].

Common Name: Southwestern White Pine

General Information

Pinus strobiformis is an evergreen tree with a narrow conical crown that becomes rounded to irregular with age; it can grow up to 30 metres tall. The straight, cylindrical bole can be 90cm in diameter[].
The tree is harvested from the wild for local use as a food and source of medicines and materials. It is harvested commercially for its wood, which is considered to be of good quality for construction and carpentry[].
The range of Pinus strobiformis is very extensive and it is common to abundant in pine forests in the Sierra Madre Occidental and elsewhere. There may be some decline due to exploitation of timber trees in some localities, but overall the population can be considered stable. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

The wood, sawdust and resins from various species of pine can cause dermatitis in sensitive people[].

Botanical References

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Range

South-western N. America - Arizona, New Mexico and western Texas, south through Mexico to Veracruz and Puebla.

Habitat

Mixed conifer-oak woodland, often forming small areas of pure stands, favouring north-facing slopes and the sides of mountain streams, also on arid to moist summit elevations; at elevations from 1,900 - 3,500 metres[, ].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	25.00 m
Growth Rate	Medium
Pollinators	Wind
Self-fertile	No
Cultivation Status	Wild

Cultivation Details

Pinus strobiformis is a tree of moderate to high elevations, it ranges from the semi-arid regions of southwestern USA, through the mountain ranges of Mexico. The climate in the Sierra Madre Occidental of Mexico is characterized by summer rains (thunderstorms) as well as winter precipitation; winter snows are common at the higher elevations[]. Cold-tolerance of this species is said to be short periods with temperatures falling to around -10°c[], although another report suggests it can withstand -25°c[].
Pine species in general require a sunny position if they are to grow well and, whilst the different species have their own soil preferences, most will thrive in a light well-drained sandy or gravelly loam[, ]. Grows in the wild on sites with relatively deep, humus-rich though often rocky soils[]. Dislikes poorly drained moorland soils[]. Established plants tolerate drought[]. Plants are fairly wind-resistant[].
Seed production in the wild consists of a cycle of one good year followed by several years of low crops[].
The branches are very flexible[].
The broadly lance-cylindrical seed cones are 15 - 25cm long, taking two growing seasons to reach maturinty. They open and shed their seeds whilst still attached to the tree, falling soon thereafter[, ].
This is one of several species of pine that have a mutualistic relationship with species of birds in the family Corvidae (in this case Jays and Nutcrackers) to disperse its seed. The birds have powerfull beaks which enable them to extricate the seeds and crack the shells. They store many of the seeds at some distance from the parent plant - some of these seeds never get eaten and can germinate and grow into new trees[].
Plants are strongly outbreeding, self-fertilized seed usually grows poorly[]. They hybridize freely with other members of this genus[].
This species is closely allied to Pinus flexilis[]. In the northern part of its range, Pinus strobiformis overlaps with Pinus flexilis and reportedly hybridizes with it[].
This species is very susceptible to white pine blister rust[]. It should not be grown near any gooseberries or currants (Ribes species) since these plants can act as vectors for the disease[, ].
Plants in this genus are notably susceptible to honey fungus[].

Edible Uses

Seed - raw or cooked[, ]. They can also be ground into a powder. Rich in oil, the seed has a slightly resinous flavour and a soft texture, it makes an excellent food[]. The red-brown, ovoid seed is about 10 - 13mm long and 10mm wide[, ] and has a harder shell than the pinyon pine seeds[].

Inner bark. There are no more details but inner bark is often dried, ground into a powder and then used as a thickener in soups etc or added to cereals when making bread.

A vanillin flavouring is obtained as a by-product of other resins that are released from the pulpwood[].

Medicinal

Oil of turpentine, obtained from the oleo-resin of all pine trees, is antiseptic, antispasmodic, astringent, diuretic, rubefacient, stimulant and vermifuge[, ]. It is a valuable remedy used internally in the treatment of kidney and bladder complaints and is used both internally and as a rub and steam bath in the treatment of rheumatic affections[]. It is also very beneficial to the respiratory system and so is useful in treating diseases of the mucous membranes and respiratory complaints such as coughs, colds, influenza and TB[].
Applied externally in the form of liniment plasters, poultices, herbal steam baths and inhalers, it is a very beneficial treatment for a variety of skin complaints, wounds, sores, burns, boils etc[].

Agroforestry Uses:

The needles contain a substance called terpene, this is released when rain washes over the needles and it has a negative effect on the germination of some plants, including wheat[].

Other Uses

A tan or green dye is obtained from the needles[].

A resin obtained from the plant is harvested for medicinal use[]. Oleo-resins are present in the tissues of all species of pines, but these are often not present in sufficient quantity to make their extraction economically worthwhile[]. The resins are obtained by tapping the trunk, or by destructive distillation of the wood[, ]. In general, trees from warmer areas of distribution give the higher yields[].
Oil of Turpentine consists of an average of 20% of the oleo-resin[] and is separated by distillation[, ]. Turpentine has a wide range of uses including as a solvent for waxes etc, for thinning and dissolving varnish and paints, a shoe polish, medicinal etc[, ].
Rosin is also obtained by distillation of pine resin. This is used in paper glue and soap manufacturing, as a constituent of varnishes and paints, and for coating the bows of stringed musical instruments such as violins[, ].
Pitch can also be obtained from the resin and is used for waterproofing, as a wood preservative etc[].

The wood is light in weight, soft, close-grained. Of good quality, it is used in construction and for carpentry, and is also considered to be a good wood for making violins[, , , ].

Propagation

It is best to sow the seed in individual pots in a cold frame as soon as it is ripe if this is possible otherwise in late winter. A short stratification of 6 weeks at 4°c can improve the germination of stored seed[]. Plant seedlings out into their permanent positions as soon as possible and protect them for their first winter or two[]. Plants have a very sparse root system and the sooner they are planted into their permanent positions the better they will grow[]. Trees should be planted into their permanent positions when they are quite small, between 30 and 90cm[]. We actually plant them out when they are about 5 - 10cm tall. So long as they are given a very good weed-excluding mulch they establish very well[]. Larger trees will check badly and hardly put on any growth for several years. This also badly affects root development and wind resistance[].
Cuttings. This method only works when taken from very young trees less than 10 years old. Use single leaf fascicles with the base of the short shoot. Disbudding the shoots some weeks before taking the cuttings can help. Cuttings are normally slow to grow away[].