White fir

Synonyms: Picea concolor, Picea lowiana, Abies lowiana, Abies grandis var. Lowiana, Pinus concolor, Abies grandis var. Concolor, Pinus lowiana, Abies concolor var. Lowiana, Abies concolor f. Atroviolacea Cinovskis, Abies concolor subsp. Lowiana, Abies concolor var. bajacalifornica Silba, Abies concolor var. martinezii Silba, Abies lowiana var. viridula Debreczy & Rácz

White fir – a species of evergreen monoecious trees of the genus Abies in the pine family (Pinaceae). Naturally occurs in the southwestern and western parts of North America. Cultivated as an ornamental plant in steppe, forest and subtropical zones practically worldwide – Europe, North America, the Far East, Australia, South Africa.

It was discovered in 1849—1853 by the English plant collector William Lobb during his expedition to California. It was first described in the scientific literature in 1858 by the British botanist George Gordon in his monograph "The pinetum: being a synopsis of all the coniferous plants at present known, with descriptions, history, and synonymes, and comprising nearly one hundred new kinds". The Latin name Abies concolor first appeared in 1861 in the work of Friedrich Hildebrand and John Lindley.

The species received its name because of the same bluish-green coloration on both sides of the needles.

It is a tall and powerful tree reaching up to 60 m in height. The trunk can reach 1.9 m in diameter. The tree is fast-growing. It lives up to 350 years. The crown in youth is dense and broadly conical; with age it becomes pendulous and relatively sparse. The apex of young trees is sharp and spire-like; in old trees it becomes flatter.

Bark hard, gray, smooth, with thickness at the base of trees reaching 10-15 (18) cm, with deep longitudinal grooves. It is fairly fire-resistant. Main branches grow at right angles to the trunk, with age they droop slightly. Branchlets are smooth, small, covered with a yellowish pubescence, and oriented upwards. Buds are resinous, blunt, yellow-green, reaching 6 cm in length.

Foliage flat, green or bluish-green, with gray-white lines on both sides, falcate, bluntly or rounded-pointed at the tip, asymmetrically attached, with a slightly expanded base. Reaches 1.5-6 cm in length and 2-3 mm in width. Stomata are arranged in 4-8 rows on the lower surface of the needle on both sides of the midrib. On the upper side there are also 7-12 (5-18) rows of stomata. Needles have a strong camphor scent.

Male strobili are purple or red, female ones are green. Cones are sessile, large, ovoid-cylindrical, 7-12 cm long and 3-4.5 cm wide. When beginning to ripen they are olive-green, later becoming yellow- and dark-brown. Scale size 2.5-3 x 2.8-3.8 cm. Seed scales are longer than the bracts.

Seeds brown, with a pinkish wing, 8-13 mm long. They contain 5-7 (5-9) cotyledons. 1 kg contains 22,000-33,000 seeds. Thousand-seed weight on average – 35 g. Fruiting occurs every 1-3 years.

Chromosome number: 2n=24

Hardiness zone: 4b (-30 °C). Due to late bud break it is practically not affected by spring frosts.

Location/siting: hardy to adverse conditions. Wind- and drought-resistant. Shade-tolerant, but grows well in good light. In the first years after planting it needs shading. White fir prefers high air and soil humidity but does not tolerate waterlogging. Some forms may suffer from air pollution.

Planting: in avenue plantings the recommended distance between trees is at least 4-5 m, in dense groups – 2.5 m, in loose groups – 3-3.5 m. Optimal planting time: spring in April, autumn – late August through September. Minimum planting hole size: 50x50x60 cm. The root collar should be at ground level. Recommended soil composition: peat, sand, clay, leaf mold or humus in a ratio of 1:1:2:3. On heavy soils drainage is mandatory – a 20 cm layer of crushed brick or rubble is placed at the bottom of the hole. When planting it is recommended to add nitroammophoska in the amount of 250-300 g per hole and 10 kg of sawdust. Optimal planting age – 5-10 years.

Care: does not like transplanting. In the 2nd-3rd year after planting it is recommended to apply Kemira-Universal (150 g/m2). Loosen the soil to a depth of 25-30 cm. Mulch the trunk circle with sawdust, peat or wood chips in a layer of 5-8 cm. Young plants need to be covered with conifer branches in severe winters.

Pruning: sanitary pruning is carried out in early spring. Formative pruning is performed in early spring before sap flow.

Diseases and pests: affected by the spruce-fir adelgid. Seeds are damaged by cone-attacking wasps. In winter needles may be damaged due to sharp temperature fluctuations.

Uses: in its native range the wood is used in carpentry and construction; woodworking residues are used for pulp production. In landscape design it is used to create color contrast. It looks good in solitary and group plantings with larches, white-barked birches, maples and deciduous shrubs. Also used to create untrimmed living screens. Because fir needles do not fall off quickly, branches of this tree are widely used in floristry. As a covering material, conifer branches are not recommended, as dense needles poorly transmit light and air.