White fir is an especially beautiful coniferous evergreen. It has a pyramidal shape and light blue-green needles (similar to blue spruce). These needles, like those of most firs, are flat instead of sharp---making them easier to work around than other evergreens. The light green cones are relatively small---up to 5 inches long, and are shaded purple when young. White firs tend to keep their older branches and do not get scraggly as they age.
- Common name: White fir
- Botanical name: Abies concolor
- Zones: 3 to 7
- Size: To 150 feet tall and 25 feet wide
- From: Areas of North America
- Family: Pinaceae (pine family)
- Sun: Full sun is best; they will tolerate partial shade.
- Soil: Ensure that the soil retains moisture, but still drains well. This plant prefers a soil rich in organic matter---add organic matter to the area before planting. Avoid heavily compacted soils and heavy clays.
- Moisture: Though white firs are drought tolerant, watering during times of drought will keep the trees looking healthy.
- Zones: 3 to 7
- Mulch: A 2- to 3-inch-deep layer of mulch over the soil around the tree will help conserve moisture, reduce competition from weeds or turf grass, and protect the tree's bark from damage from lawn mowers or string trimmers. Leave a 4-inch gap between the mulch and the tree's trunk.
- Pruning: Pruning is unnecessary if the tree is sited well. When necessary, pruning is best done in early summer when the new growth (called candles) appears. Remove no more than half of the candle.
- Fertilizer: In most soils, fertilizing is unnecessary. Use a balanced fertilizer in spring if necessary.
- Seed: Gather seeds from ripe cones in spring. Soak the seeds in water for several days, then plant them and keep them at temperatures less than 40F for six weeks or more.
- Cuttings: Take hardwood cuttings in mid- to late winter.
- Adelgids: Adelgids cause new growth to become deformed and discolored. Galls---which look like cancerous growths---from these insects are usually present on stems. Unfortunately, you cannot protect the trees from adelgids. Frequently spraying small trees with a stream of water may help prevent adelgid populations from growing too large.
- Aphids: These small insects often appear in large numbers on new growth. Spray them off daily with a stream of water; they will not attack a plant after being knocked off. Treat large infestations with insecticidal soap.
- Borers: These insects bore tunnels beneath the bark. You might see small holes with sawdust beneath them. To deter borers, encourage beneficial insects and use horticultural oil while the trees are dormant.
- Canker: Forms dark water-soaked cankers on the bark and branches of the tree. The cankers can spread, becoming larger. To deter the disease, prune off any infected branches, dipping your pruning tool in a bleach or alcohol solution between cuts.
- Mistletoe: This parasitic plant sometimes attacks white firs. Cut mistletoe from the plant as soon as you notice it. If young branches are affected, remove them entirely.
- Rust: This fungal disease appears as rusty-colored patches on the bark and needles of the fir. These patches are usually followed by small masses of rusty-colored powder. To deter the disease, avoid wetting the needles; make sure there is good air circulation between trees.
- White fir is often used as a Christmas tree because of its soft needles and good water-retaining ability.
- Many evergreens, including white firs, are susceptible to winter browning. To help prevent this problem, called winterburn, ensure that the plants get plenty of moisture in autumn. Also: Watering in winter on days when the temperature rises above freezing can help.
- Abies concolor ‘Argentea': This cultivar bears needles that are more silvery-green than the species, making it very ornamental.
- Abies concolor ‘Compacta': A dwarf cultivar which resembles the species, except it only reaches about 15 feet tall and is much slower-growing.
- Abies concolor ‘Globosa': A dwarf selection with a rounded, mound-like form.
- Abies concolor ‘Pendula': A favorite cultivar with branches that slowly "weep" or droop as they age.
- Abies concolor ‘Violacea': This selection resembles the species, except the foliage is more silvery blue than silvery green.