Jooni

An exemplary photo of a Fir bonsai

Fir

4 Species

Species

Abies alba Abies koreana Abies lasiocarpa Abies lasiocarpa var. arizonica

Fir (Abies spp.; for bonsai mainly the Korean fir A. koreana, the Japanese fir A. firma and the Nikko fir A. homolepis) is a cold-hardy evergreen conifer from cool mountain forests. A fir bonsai is an outdoor tree that needs a cold winter rest and suffers in hot, dry summers.

It suits growers with some experience rather than complete beginners, mainly because firs bud back poorly from bare old wood and dislike heat. In return, its soft, flat needles, naturally tiered branches and, in the Korean fir, upright violet-blue cones make a very elegant, forest-like conifer bonsai.

At a glance Abies spp.

Difficulty
Intermediate
Placement
Outdoors
Light
Sun to partial shade
Watering
Moderate
Min. temperature
-10°C (14°F)
Foliage
Evergreen

Fertilizing

Feed from spring until early autumn with solid organic fertilizer once a month or a balanced liquid fertilizer at half strength every 1–2 weeks. Young trees in development can be fed more generously; refined trees get less, to keep needles and internodes short.

  • Do not feed during winter dormancy.
  • Avoid overfeeding, which produces long, coarse needles.

Placement

Keep the tree outdoors all year in full sun to partial shade, with shade from the hot afternoon sun in summer. Firs come from cool, moist mountain climates, so a shade cloth helps during heat waves.

Firs are very hardy, but roots in a pot are much less so. Protect the pot once frosts drop below about -10°C (14°F), for example in a cold frame or unheated greenhouse with good light and ventilation.

Pruning

In spring, pinch or cut back the soft new shoots once they extend, removing the strongest central shoot of each tuft to balance vigor. Always leave needles on every branch, because firs rarely bud back from bare wood.

Do structural pruning in late autumn or late winter, outside the growing period. Leave longer stubs on removed branches and turn them into jin later.

  • Wire from autumn to late winter, when the tree is not growing.
  • Branches take a long time to set, so use guy wires for thick branches.
  • Remove wire before it bites in; scars on fir bark stay visible for years.

Repotting

Repot young trees every 2–3 years and older trees every 3–5 years, in early spring as the buds begin to swell. Prune the roots moderately and never remove more than about a third.

  • Use a free-draining mix such as akadama, pumice and lava rock in roughly equal parts.
  • Firs prefer slightly acidic conditions, around pH 5.5–6.5.
  • Make sure the pot drains freely: firs rot quickly in wet soil.

Watering

Water thoroughly when the soil surface begins to dry, avoiding both drought and constant wetness. In summer, also mist the foliage in the evening, as firs like cool, humid air.

  • In winter, water less, but never let the root ball dry out, even when frozen weather alternates with mild spells.
  • Use rainwater if your tap water is hard and alkaline.

Seasonal care

  • Spring: Repot every 3–5 years as the buds swell, start feeding and pinch the new shoots once they extend. Protect tender shoots from late frosts.
  • Summer: Shade the tree from the afternoon sun, water carefully and mist in the evening. Keep feeding at half strength.
  • Autumn: Stop feeding in early autumn and carry out structural pruning and wiring once growth has stopped.
  • Winter: Keep the tree dormant outdoors and protect the pot from frosts below about -10°C (14°F). Water sparingly and check the wire.

Common problems

Most problems with fir bonsai come from heat, wet roots or a few sap-sucking pests.

  • Brown needle tips and needle drop: Usually caused by summer heat, strong sun or a dried-out root ball. Provide afternoon shade, mist in the evening and water consistently.
  • Root rot: Yellowing needles and weak growth in soil that stays wet. Repot into a free-draining mix and let the surface dry slightly between waterings.
  • Adelgids: White, woolly tufts on shoots and needles, sometimes with distorted growth. Rinse them off and treat with horticultural oil or insecticidal soap.
  • Spider mites: Speckled, dull or yellowish needles, especially in hot, dry weather. Mist the foliage regularly and treat with a miticide if needed.