Birch sap

Betula pendula

When: Typically March – April — March, April. Earlier in warm, low country; later in the hills.
Where it grows: Birch woods, heaths and parks — silver and downy birch, on any big, healthy tree.
How to know it: Silver birch has white, papery bark that cracks into black diamonds at the base and drooping twig tips; downy birch has duller bark and upright, downy twigs. Both are tapped. The sap runs for a few weeks in early spring, before the leaves open.
Look-alikes: Tap only trees you can name by their bark in bare-branched spring. Birch sap is the drink; most other trees’ sap is not.
Harvest and use: Drunk fresh — clear, faintly sweet and silky. It sours within two or three days, so drink it, freeze it, or let it ferment.
Caution: Tapping wounds the tree and lets in decay. One small hole in a big, healthy birch, plugged afterwards — and only with the landowner’s permission: everyman’s right covers berries and mushrooms, not tapping trees.

Birch sap at a glance

Also called: Birch water, birch juice; mahla (Finland), kasemahl (Estonia), bērzu sula (Latvia), sok z brzozy (Poland), berezovyi sik (Ukraine), björksav (Sweden)
Family: Betulaceae (birch family)
Where it grows: A traditional spring drink across the boreal and hemiboreal north and east of Europe — Finland, Sweden, Norway, the Baltic states, Poland, Belarus and Ukraine — and tapped in France, Scotland and elsewhere too. Silver birch itself grows across Europe as far south as Spain.
When to pick: Only at the turn of winter and spring, while the sap is rising hard and before any green leaves appear — about a month in all. Once the leaves open, the sap turns bitter.
Parts used: The sap, fresh or naturally fermented. Boiled down, it makes birch syrup, a rare and expensive product.

Questions people ask about birch sap

When can you tap birch trees?

In early spring, before the leaves break — roughly March in the south and April in the Nordic countries. The run lasts about a month, and sap taken after the leaves open is bitter.

How long does birch sap keep?

Barely: two to five days in the fridge. After two or three days it starts to ferment and turn sour. Freeze it if you want to keep it.

Does tapping hurt a birch tree?

It wounds it. Tapping holes consistently stain the wood, and one study found decay spreading from more than half of old tap holes; birches tolerate tapping less well than maples. Drill one small hole in a big, healthy tree, and plug it when you finish.

What does birch sap taste like?

Like very soft water with a faint sweetness and a silky feel. As it ferments it turns tart.

Found in these regions

Hardiness zones 2–7.

Is it ready near you?

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Checked against these sources · last reviewed October 2026

Seasons are typical for the middle of the range and move by weeks north and south, and up and down hills.

Educational information only. Never eat a wild plant or mushroom identified from a single photograph or description — confirm with a regional field guide or an experienced forager, and know the poisonous species in your area first.

Birch sap

Betula pendula

When

Typically March – April — March, April. Earlier in warm, low country; later in the hills.

Where it grows

Birch woods, heaths and parks — silver and downy birch, on any big, healthy tree.

How to know it

Silver birch has white, papery bark that cracks into black diamonds at the base and drooping twig tips; downy birch has duller bark and upright, downy twigs. Both are tapped. The sap runs for a few weeks in early spring, before the leaves open.

Look-alikes

Tap only trees you can name by their bark in bare-branched spring. Birch sap is the drink; most other trees’ sap is not.

Harvest and use

Drunk fresh — clear, faintly sweet and silky. It sours within two or three days, so drink it, freeze it, or let it ferment.

Caution

Tapping wounds the tree and lets in decay. One small hole in a big, healthy birch, plugged afterwards — and only with the landowner’s permission: everyman’s right covers berries and mushrooms, not tapping trees.

Birch sap at a glance

Also called

Birch water, birch juice; mahla (Finland), kasemahl (Estonia), bērzu sula (Latvia), sok z brzozy (Poland), berezovyi sik (Ukraine), björksav (Sweden)

Family

Betulaceae (birch family)

Where it grows

A traditional spring drink across the boreal and hemiboreal north and east of Europe — Finland, Sweden, Norway, the Baltic states, Poland, Belarus and Ukraine — and tapped in France, Scotland and elsewhere too. Silver birch itself grows across Europe as far south as Spain.

When to pick

Only at the turn of winter and spring, while the sap is rising hard and before any green leaves appear — about a month in all. Once the leaves open, the sap turns bitter.

Parts used

The sap, fresh or naturally fermented. Boiled down, it makes birch syrup, a rare and expensive product.

Questions people ask about birch sap