We know the festive season is upon us when Christmas displays appear in the shops and Radio 2 is playing Silent Night. So what better genus to discuss this week than Abies?
The firs are fast becoming the favourite tree for Christmas. UK customers can choose between the non-drop species A. nordmanniana (Nordmann Fir), A. procera (Noble Fir) and A. fraseri (Fraser Fir).
But for many people a tree is not just for Christmas. The larger species of Abies, such as A. grandis and A. cephalonica can grace large estates and parklands. Some species suit a smaller garden, such as A. koreana and A. delavayi var. forestii, and there are many dwarf varieties for the rock garden aficionado.
The genus is made up of around 50 species of evergreen conifer that grow in mountainous regions in Europe, northern Africa, Asia and North America. They can range from 10m to 60m tall and dwarf forms have been bred as small as 50cm, but often spread more.
They bear needle-like leaves that are mid to dark green and often have two silver bands on their underside. Another distinctive feature is the female cones, which are cylindrical and usually purplish blue, standing erect on the upper branches.
Abies generally do best in a fertile, well-drained soil that is reasonably moist throughout the year. Planting is best done in early to mid autumn, but on sites that stay cold and wet over winter it should be delayed until early spring. They are best planted when they are still small - under 60cm tall - because more mature specimens tend to have checked growth and can produce odd-looking, bunched branch whorls. Abies tend to be slow to establish and become stocky before they produce a growth spurt upwards.
Trees can have double leaders so one should be selected. Grafted trees may also need to be encouraged to develop an erect leader. Once the trees begin to shoot upwards, some of the lower branches can be removed, but this cleaning of the bottom 2m of the trunk should be carried out in stages. As with all trees, creating a circle around the trunk free of weeds and turf is advisable to give them the best chance of establishing and obtaining moisture.
Propagation can be carried out by sowing seed when ripe or in late winter. Seed should be stratified for 21 days to aid germination. Grafting can be done in winter. Abies is prone to attack by adelgids and is in danger of contracting honey fungus like many trees, but is said to be the most resistant conifer to Armillaria species.
What the specialists say
- Robert Williamson, conifer specialist, Ashwood Nurseries, West Midlands
"Abies is a useful genus for the garden, particularly the dwarf cultivars that make good garden plants, providing colour and structure year round. Its key features are disease resistance, growth habits, varying colours and large cones.
"I have three particular favourites: A. pinsapo, especially 'Horstmans Nana', because it is a very good dwarf variety that retains the leaf details of the larger species; A. koreana because it has reasonably slow growth habit and excellent pyramidal shape and white reverse to the needles; and A. procera 'Glauca' with its lovely blue foliage - ideal for the larger garden.
"Abies like a good fertile loam with reasonable moisture all through the year and apart from that they are very easy to grow. They don't really suffer from anything, but they are possibly susceptible to honey fungus."
- Gordon Haddow, owner, Kenwith Conifer Nursery, Devon
"Abies is used in various parts of the world for timber production. A single specimen holds its bottom branches, giving a fully clothed appearance like the spruce. It is a healthy tree although one species, A. balsamea and some of it's cultivars, now appears prone to Phytophthora.
"Species such as alba, nordmanniana, pinsapo, concolor, grandis and fraseri have produced good dwarf garden forms. But A. koreana stands out as the best species, having produced numerous first-class garden plants. Many, such as the new dwarf 'Icebreaker', show the silver reverse of the leaves.
"Abies do best in a free-draining soil and an open situation with good air circulation, but avoid planting balsamea cultivars in damp situations or give them a miss altogether."
- Simon Toomer, director, Westonbirt Arboretum, Gloucestershire
"Three main attributes make silver firs worthy garden plants - size and form, ornamental evergreen foliage and cones. For large spaces such as parks, gardens and historical parks, the large species such as the Grand Fir, Caucasian Fir and Greek Fir make impressive specimens. The latter is among a few species tolerant of shallow chalky soils - most thrive best on moister more fertile sites.
"My experience of growing silver firs at Westonbirt is that they are best planted while still small. Even so, they are often quite slow to establish or become quite 'stocky' before they put on a spurt of upwards growth.
"Most species are too large for smaller spaces but A. koreana is an exception, rarely reaching 15m and usually much smaller. This species combines the small stature with beautiful purple-blue cones borne from a young age. This habit is shared by the less familiar A. delavayi var. forestii, which is even smaller at around 10m in height.
"For gardeners with limited space and a taste for ornamental foliage, a number of cultivars are available including A. lasiocarpa 'Compacta', A. balsamea 'Hudsonia' and A. magnifica 'Prostrata'."
Species and varieties
A. balsamea Hudsonia Group Award of Garden Merit (AGM) (H4) are slow-growing, dwarf evergreen conifers bred from the North American species. They have a compact bun-shaped habit, short, dense branches and needles that are dark green above and blue-green beneath. Height: 1m. Spread: 1.5.m.
A. balsamea 'Nana' is a dwarf evergreen conifer with a rounded habit and tidy green foliage. Hardy down to -15 degsC. Give it some protection from hot summer sun. An ideal plant for the rock garden because of its slow growth. Height: 60cm. Spread: 1.2m.
A. balsamea 'Piccolo' is a truly dwarf form. It has fresh green foliage in early summer that looks fantastic against older dark blue-green foliage. Height: 50cm. Spread: up to 1.5m.
A. cephalonica 'Meyer's Dwarf' is a broad, low cultivar that bears blue-green chubby needles. Tolerant of hot conditions. Good for a rockery or bank. Height: 1m. Spread: 2m.
A. concolor AGM (H4) is a slow to medium growing fir with silvery blue-green needles that are blunt at the tips. They have a bluey-white underside that shows as the needles point upward and forward along the shoots. Young trees are conical, slowly maturing with a dome-like crown. Height: 20m. Spread: 5m.
A. concolor 'Compacta' has a very compact habit with irregular form and steely blue needles. Maximum height and spread: 60cm.
A. grandis is the Grand Fir, a large conifer that can reach 60m at maturity. It has a straight trunk, compact canopy and deep glossy green, fragrant needles with silvery undersides and cigar-shaped cones. Used in forestry plantations throughout Great Britain.
A. koreana is a small pyramidal tree with a handsome straight stem, notched stubby needles and attractive cones that are purple when young. It can be used as a non-drop Christmas tree. Needs a deep, moist soil for good development. Avoid polluted areas and chalky soils. Height: 10m.
A. koreana 'Silberlocke' AGM (H4) is a very popular cultivar with dark-green needles that curl upwards to show the silvery white undersides. Bears purple cones like its parent. Maximum height 4m. Spread: 1.5m.
A. nordmanniana AGM (H4) is the Nordmann Fir, the most popular non-drop Christmas tree in Britain. It becomes a large tree with a narrow conical or columnar crown. It has glossy, dark-green needles, dull white beneath, that point forwards and overlap. It produces greenish-brown cones with protruding bracts. Good for shelter. Height: 40m. Spread: 6m.
A. nordmanniana 'Golden Spreader' AGM (H4) forms a spreading bushy plant that can develop a leader and become conical. It has bright golden-yellow foliage that really stands out, particularly in winter. Height. 1m. Spread: 1.5m.
A. pinsapo 'Glauca' AGM (H4) is a slow-growing, medium-sized conifer with blunt grey-green needles arranged all round the shoot. Cones are pale green or purple when young, ripening brown. Height: 15m. Spread: 8m.
A. procera 'Glauca' becomes a large tree with a pyramidal, upright habit. It has lovely powder-blue needles and produces tall, upright cones that are also blue. Slow growth until established, then moderate. Height: 20m. Spread: 8m.
Thank you to Floramedia, which supplied the images for this article from its photo library www.floramedia-picture-library.com.