Common Name: Limber Pine

General Information

Pinus flexilis is an evergreen tree with a much-branched, conical crown that becomes rounded with age; it can grow up to 26 metres tall. The straight to contorted bole can be up to 200cm in diameter. Side branches are often persistent right down to the trunk base[].
The plant is harvested from the wild for local use as a food, medicine and source of materials. It is little utilized for timber because of its strongly tapering trunk and much-branched form[]. It is sometimes grown as an ornamental, there are some named varieties[].
Pinus flexilis is experiencing declines due to White Pine Blister Rust and Mountain Pine Beetle. However, there have been no wide-scale extirpations of plant populations and the range of the species has not contracted since the last assessment. Therefore the plant is still 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

Western central N. America - Alberta to North Dakota, south to California, Arizona and New Mexico.

Habitat

High montane forests, often forming open forests in the sub alpine to alpine zones, often in semi-arid areas; growing at elevations from 1,500 - 3,600 metres[, , ]. Usually found on dry rocky ridges and peaks[].

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	Ornamental, Wild

Cultivation Details

Pinus flexilis is a very cold-hardy plant, able to tolerate temperatures down to around -35°c when fully dormant[].
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[, ]. Dislikes poorly drained moorland soils[]. Established plants tolerate drought[]. A fairly wind-resistant species[], the plants often colonise exposed mountain slopes in the wild, their deep taproot anchoring them firmly[, ].
A long-lived but slow-growing tree in the wild[]. Growth in Britain can be fairly fast, over 30cm a year has been recorded[]. It is slow to get started but then grows away quite well[]. It only makes a small tree in cultivation[]. Seed production in the wild consists of a cycle of one good year followed by several years of low crops[].
The seed cones are 7 - 25cm long. They take two growing seasons to mature then open and shed their seed whilst still attached to the tree[, , ].
This is one of several species of pine that depend upon a mutualistic relationship with a species of bird (in this case Clark's nutcracker, Nucifraga columbiana) 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 albicaulis[], differing mainly in the cones[].
Plants in this genus are notably susceptible to honey fungus[].

Edible Uses

Seed - raw or cooked[, , , , ]. The oil-rich seed has a delicious flavour with a hint of resin[]. The seeds can also be ground into a powder and used in making bread, biscuits, as a thickener in soups etc[]. A reasonable size, the seed is up to 11mm x 9mm[], with a thick shell[].

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[].
A fairly wind resistant tree, it can be grown as part of a shelterbelt planting[].

Other Uses

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

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, smelling of turpentine when freshly cut. It is occasionally made into lumber and is also used for general carpentry[, , , ].
The wood is used for fuel.

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[].