Fir, <em>Abies</em>: planting, pruning and care

Description and botany

Genus Abies groups nearly fifty species of evergreen conifers of family Pinaceae to which pines and spruces also belong. Douglas fir belongs to another genus Pseudotsuga menzieisii, recognisable by its pendulous cones provided with bracts bearing three points. Abies are generally large trees recognisable at a distance by their slender conical silhouette and by their elongated upright cones at branch tips instead of being pendulous as in genus Picea or Pseudotsuga.

Most firs grow in upland areas with cool or cold climates or near the sea such as Vancouver fir (Abies grandis) and noble fir (Abies procera), and occur exclusively in Northern Hemisphere, notably in China and western North America. Some species are however found on mountain summits in tropical regions of Central America and Southeast Asia, and a few rare species are perfectly adapted to drought such as Spanish fir (Abies pinsapo) and Cephalonia or Greek fir (Abies cephalonica).

Abies alba – botanical illustration

Firs have a cylindrical trunk that is smooth, grey and covered with resin blisters until bark hardens with age. Branches regularly spaced around trunk in whorled tiers give this conical silhouette much appreciated for highlighting Christmas decorations. Firs’ buds are generally round. Firs often live for more than two or three centuries; growth is generally slow during first 10 years and then accelerates, except in dwarf varieties offered for ornamental gardens.

Firs’ needles are short leaves (1 to 7 cm long) , flat and stiff but not prickly, with blunt or sometimes notched tips, most often arranged in two ranks and with two white bands of stomata (movable cells allowing gas exchange) on underside. However Abies pinsapo, koreana and basalmea are exceptions with their short brush-like needles distributed all around the shoot and with white bands on both faces. Abies bracteata, native to a restricted area of California, is a distinctive species that bears long prickly needles and buds as pointed as those of beech. Bluish-grey tones are often much sought after and result from selections among wild populations, as in Colorado fir (Abies concolor), noble fir (Abies procera) or Spanish fir (Abies pinsapo).

Quick tip to tell a spruce shoot from a fir shoot: Pull on a needle: if a piece of bark is torn away, it is a spruce; if a neat round scar remains on the shoot, it is a fir.

Fir flowering is monoecious, male aments yellowish, greenish or reddish and laden with pollen open in April or May towards base of tree on one-year-old shoots. Female flowers or conelets located on branches at tree top form after fertilization cylindrical upright cones that detach or disintegrate scale by scale under effect of summer drought or squirrels, leaving an upright axis on the shoot. Cones are sticky, exuding droplets of resin at maturity and take one year to mature. They bear bracts more or less protruding, particularly long and tapered in Abies bracteata giving them a hedgehog-like appearance. Triangular seeds are winged and have short germination longevity.

Fir is valued for its pale wood, easy to work both for construction, joinery and for paper pulp. Vosges turpentine is extracted from resin of common fir (Abies alba) as well as an essential oil from its needles used to treat respiratory infections.

Fir honey is strongly aromatic and balsamic with a faint resin scent.

Abies nordmanniana (famous Nordmann fir) / Abies koreana

Main fir varieties

Vigorous varieties

Low-vigour varieties

Dwarf varieties

Abies koreana Silberlocke - Korean Fir

Forms a magnificent bush with a dense, pyramidal habit, regularly tiered branches covered in very recurved needles with a silvery underside that catch the light and the eye. Pretty upright cones, at first green then turning powdery blue‑violet, even appear on young specimens.

• Height at maturity 3,50 m

See the product sheet

Abies alba Pyramidalis - Dwarf White Fir

Dwarf form of Vosges fir with a columnar to conical silhouette clothed in very dense, very dark foliage with a silvery underside, soft to the touch. In spring, young shoots are a creamy yellow, and in summer the foliage bears small upright green cones that later take on a lovely purplish or reddish-brown hue. Best suited to humid situations free from late frosts.

• Height at maturity 2,50 m

See the product sheet

Abies koreana Nadelkissen - Korean Fir

Pretty neat little ball of bright light green, perfect for small gardens, rockeries or containers, in well-drained, cool soil, sheltered from scorching sun. In spring, its small prominent brown buds borne at branch tips add colour to the foliage.

• Height at maturity 35 cm

See the product sheet

Abies nordmanniana subsp. nordmanniana Münsterland - Fir

Prostrate variety of Caucasian fir covered in dense, glossy bluish-green foliage. Hardy and slow-growing, tolerates cool to dry soil, even calcareous, but does not tolerate pollution. Perfect in rock gardens, rocky scree, for decorating a small garden or an attractive container.

• Height at maturity 30 cm

See the product sheet

Abies balsamea Piccolo

Dwarf variety of balsam fir with a stocky, very compact habit, fine soft foliage dark green with a spicy scent. In spring, its prominent brown buds borne at the tips of almost vertical branches add colour to the whole. With slow growth and small size, perfect for small gardens, rockeries or containers.

• Height at maturity 45 cm

See the product sheet

Planting

Where to plant fir?

Firs grow in any deep, cool, well-drained ordinary soil. Some species, however, do not tolerate calcareous soil such as nobilis and grandis, unlike nordmaniana and pinsapo, for example. The latter even tolerate dry soils and make very attractive specimens in southern France.

Nikko fir, Abies homolepis, is one of the few to tolerate urban pollution and drought. It rarely exceeds 5–10 m in height and produces young bright-purple cones from an early age, as does koreana, a species also highly ornamental but more demanding.

When to plant?

Prefer planting in autumn between October and December to ensure good establishment before facing summer drought.

How to plant?

This plant is easy to grow if planting is done with a little care. Fir should be planted from a rootball or container-grown specimen but never from bare roots.

• Soak the rootball in a bucket of water to fully moisten it and loosen the outer roots slightly to prevent them from circling, without disturbing them too much.
• Dig a hole 0.60 to 1 m wide and 0.50 to 0.70 m deep and aerate the soil around it with the tines of a digging fork.
• In heavy soil, add a few shovelfuls of sand and gravel to ensure good drainage around the roots.
• It is not advisable to add manure or compost because the plant is content with relatively poor soil. Add shredded horn if the soil is very poor.
• Position the plant only 5–6 cm below soil level.
• Install a stake at a slant or three vertical stakes to support the plant in strong winds.
• Refill the hole and firm the soil lightly, forming a basin.
• Water copiously and mulch if necessary.

Metasequoia glyptostroboides ‘Gold Rush’, Abies koreana ‘Silver Show’ (variety close to ‘Silberlocke’) and Picea engelmannii ‘Blush’s Lace’ in the background at Chicago Botanic Garden

Care and pruning

Firs are not pruned to preserve their beautiful conical habit. However, lower branches tend to die back through lack of light, and you can anticipate this by gradually lifting the crown, except for ball-shaped, spreading or bushy forms. It is acceptable to rebalance the profile by cutting a few small branches in October, bearing in mind that the tree does not produce new shoots on old wood.

Firs are susceptible to Chermes aphids, which induce small galls on shoots and, above all, honeydew on foliage, much appreciated by bees. If necessary, spray mineral oil on the trunk in late winter. Rust and red spider mite may occur in dry climates. Firs can also succumb to Armillaria (honey fungus) in poorly drained soil.

Propagation

Simplest propagation is sowing type species, as blue-needled colour forms are often selections that will not necessarily be found in offspring. Propagation by cuttings with a heel from lateral shoots is practised on dwarf varieties, or grafting is used, but this is a matter for professionals.

Propagation by cuttings

Prepare a deep pot by filling it with potting compost mixed with sand.

• Take August-ripened lateral shoot tips by pulling to obtain a heel.
• Remove needles from near base of cutting.
• Insert them two-thirds of their length, ensuring they do not touch.
• Firm gently all around to eliminate air pockets and ensure good contact between potting compost and cutting.
• Place them under cover in a warm, humid atmosphere.
• In autumn, separate rooted cuttings and plant them in deep pots.
• Plant young plants the following autumn in open ground.→ Discover our tutorial : How to take cuttings from conifers?

Sowing

• Sow seeds after harvest in autumn in a sandy mix or cold-stratify for spring sowing.
• Maintain cool conditions.
• Prick out young plants in September.

Uses and companion planting in the garden

Growing in deep pots of dwarf varieties or with very slow growth such as Abies balsamea Nana or even koreana is possible. These are, of course, suitable for small gardens benefiting from a humid atmosphere such as by the seaside or in the mountains. The palette of bluish or lime-green foliage in spring, adorned with brightly coloured cones as in the Korean fir, works wonders in a rock garden where graphic forms — globular, conical or spreading — can express themselves. It can be an alpine rockery planted with very colourful ground-covering perennials such as aubrieta, cerastium, or a rockery planted with heathers.

Planting combination for a bed: Abies balsamea ‘Nana’, Sedum ‘Purple Emperor’, Spirea thunbergii ‘Fujino Pink’, Rosa chinensis ‘Mutabilis’ and Berberis thunbergii ‘Atropurpurea’

Dwarf firs, associated or not with other small rockery conifers, can serve as a setting for small roses, flowering bushes such as azaleas, clumps of peonies, or even wispy grasses with a very complementary temperament. They are plants of character, benefiting from great longevity and requiring no maintenance provided they are well watered during prolonged dry spells.

The slightly more vigorous conical specimens can be planted singly, in threes or in a large windbreak hedge. These plants of strong personality provide long-lasting structure to a bed, define paths, edge the patio, easily substituting for the strong presence of clipped box.

Did you know?

Latin name Abies probably has a pre-Indo-European origin and occurs in most Romance languages (abeto in Spanish, abete in Italian) except in Romanian and French. The word ‘sapin’ comes from Gaulish sapo and is the origin of the name Savoie, which literally means ‘forest of firs’. Famous chain SPAR is named after the fir in Dutch, hence its stylised fir-tree logo.