Photo: Willow — CC BY 2.5 · source
Survives zone 2 through 7
Harvest calendar
Ripens: Early spring at the thaw — a short 2–3 week sap flow
Best planted in early spring after your last frost, or in fall before the ground freezes, depending on your climate.
Spring sap tapped for syrup or drunk fresh — around 2.6% sugar, comparable to silver birch.
- Hardiness
- Zone 2–7
- Habit
- Tree
- Edible part
- Sap
- Ripens
- Early spring at the thaw — a short 2–3 week sap flow
- Mature size
- Large tree to ~20 m — not containerable
- Light
- Full sun
- Soil pH
- 6.0–7.5 (lime-tolerant)
- Environment
- Boreal
- Native range
- Northern and central Europe and northern Asia, from Iceland, the Faroe Islands, and the British Isles east across Scandinavia and Siberia to the Lake Baikal region, and south to the Caucasus and Altai Mountains.
- Status
- Sap
- Years to fruit
- About 15 years to first seed production.
- Growth speed
- Fast while young (to about 1m/year) but short-lived, similar to silver birch.
- Spacing
- 600 cm (236 in) apart — about 36 m² (388 sq ft) per plant
- Leaf shape
- Broadly ovate to rounded-triangular leaves, 2–5.5cm long, with a single order of coarse serrations (not doubly toothed), borne on downy (pubescent), non-warty shoots — the clearest field distinction from the glabrous, warty-shooted silver birch.
- Root system
- Shallow, spreading root system; tolerant of wet, poorly-drained ground but still shallow-rooted and sensitive to compaction.
- Fruit description
- Drooping cylindrical female catkins that disintegrate at maturity to release tiny winged nutlets dispersed by wind; slender male catkins form in autumn ready to open the following spring.
- Propagation
- By seed — cuttings work but root poorly and unreliably in this genus, so seed is preferred. Sow fresh seed in a cold frame in autumn, just covering it, or surface-sow in spring under glass to raise germination temperature; grow seedlings on for about 2 years before planting out.
- Pollination
- Wind-pollinated, monoecious catkins — irrelevant to a sap crop
The edible parts listed above are a starting point, not a field guide. Identify a plant with certainty — ideally against a local authority — before eating any part of it, and read the full disclaimer. Spotted something wrong? Report it.
Growing guide
Fertilizing. Very tolerant of poor, acidic, and even boggy soils; adapts to sandy, loamy, or heavy clay ground. PFAF lists it as a dynamic accumulator that improves soil through root activity — no routine feeding is required.
How it spreads. A vigorous pioneer that self-seeds freely onto disturbed or cleared ground via wind-dispersed seed, colonising a wider range of wet and boggy sites than silver birch.
Growing tips. Fast-growing (up to about 1m/year while young) but short-lived. Tolerates poorer, wetter, and more acidic soils than silver birch, but cannot cope with deep shade or drought. In the same 20-year Ohio common-garden trial, downy birch proved considerably more vulnerable to bronze birch borer than North American paper, gray, and river birch. Shallow, spreading roots are sensitive to compaction. Sap tapped in early spring before leaf-out yields about 4–7 L/day per tap without harming the tree if holes are sealed afterward; sugar content is around 2.6%, comparable to silver birch.
Companion planting. Shares a highly bronze-birch-borer-susceptible profile with silver birch when grown near stressed trees; PFAF also notes it, like other birches, is a good plant to site near a compost heap since its leaves aid fermentation, and it supports over 200 associated insect species.
Grow journal
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