What Is Chaga? The Birch Mushroom Behind Chaga Tea
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Chaga is a fungus that grows on birch trees in cold northern forests. It doesn’t look like a mushroom at all: it forms a hard, black, cracked lump on the trunk, a bit like a chunk of burnt charcoal, with a rusty orange-brown interior. That lump, called a conk, is what people grind and steep to make chaga tea. So what is chaga, exactly? Its scientific name is Inonotus obliquus, it’s also known as cinder conk or birch conk, and it has a long history as a folk tea in Russia and northern Europe. Today it shows up in mushroom coffees, chai blends and tinctures.
This guide covers what chaga is, how it tastes, how it’s brewed, what the research does and doesn’t show, and who should be careful with it.
Key takeaways
- Chaga (Inonotus obliquus) is a fungus that grows mainly on birch in cold climates; the usable part is the hard, black conk.
- It’s too bitter and woody to eat, so it’s traditionally brewed as a tea or taken as an extract.
- Most research on chaga is from cell and animal studies; good human evidence is limited.
- Chaga contains oxalates. Case reports have linked heavy, long-term use to kidney injury, and it may interact with blood thinners and diabetes medication.
In this article
- What is chaga?
- What chaga tea tastes like
- How chaga is brewed
- What the research says
- Safety: who should avoid chaga
- FAQ
What is chaga? The birch mushroom explained
Chaga is a parasitic fungus. Its spores enter a tree through a wound, and over years it grows inside the wood. The part you can see is a sterile mass of fungal tissue (mycelium) mixed with wood, pushing out through the bark. A review in The ASCO Post describes it as a fungus that grows on birch and other trees in cold climates, also known as cinder conk, birch conk or clinker polypore.
| Chaga | |
|---|---|
| Scientific name | Inonotus obliquus |
| Other names | Cinder conk, birch conk, clinker polypore |
| Main host | Birch trees |
| Where it grows | Cold northern forests |
| What’s used | The conk: dark outer crust and orange-brown interior |
| How it’s used | Tea, powders, extracts, capsules, blends |
| Traditional use | Folk remedy in Russia, the Baltics and other northern European countries |
Is chaga a “real” mushroom?
It’s a real fungus, but the conk isn’t a fruiting body like a button mushroom or a shiitake cap. It’s more like a compact knot of fungus and wood. That’s why you won’t find chaga sliced into a stir-fry: it’s as hard as bark.
Chaga vs other “functional” mushrooms
Chaga is often grouped with lion’s mane, reishi and cordyceps in mushroom coffees and teas. They’re all different organisms with different textures and flavors. Reishi is bitter and woody too; lion’s mane is mild; chaga is the earthiest and most tea-like. For an overview of how these blends work, see what is mushroom coffee.
What does chaga tea taste like?
- Earthy and woody, like a forest floor after rain.
- Slightly vanilla-like and faintly sweet, especially from the inner conk.
- Mildly bitter, with a tannic, black-tea dryness when brewed strong.
- Dark in the cup: deep amber to almost coffee-brown.
On its own, chaga tastes plain to many people. That’s why it’s so often blended with spices, black tea or coffee, which carry its earthy base.
How chaga is brewed
Because the conk is so dense, chaga needs more time and heat than leaf tea. Common approaches:
| Form | Typical method | Notes |
|---|---|---|
| Chunks | Simmered in water for a long time, then strained | Chunks can be re-simmered; the brew gets darker the longer it goes |
| Ground or granules | Steeped in hot water, like a strong herbal tea | Quicker; strain through a fine filter |
| Powdered extract | Stirred into hot water, coffee or milk | Concentrated; follow the label serving |
| Tea blends | Brewed like the base tea | Chaga is one ingredient among several |
Whatever the form, stick to the serving size on the label, and don’t treat chaga as something to drink in large amounts every day (see safety below).
What the research says
Chaga is marketed with a long list of claims. The evidence behind them is much thinner than the marketing suggests. In a 2019 review for The ASCO Post’s integrative oncology series, the authors noted that findings on chaga’s antioxidant, anti-inflammatory and other effects come mostly from cell and animal studies, that human data are very limited, and that clinical trials are needed to confirm these effects. In short: chaga is a traditional drink with interesting lab research behind it, not a proven treatment for anything.
Safety: who should be careful with chaga
Chaga is generally consumed in modest amounts as a tea, but there are real cautions:
- Kidneys: chaga contains oxalic acid. Published case reports describe oxalate nephropathy (kidney damage) in people who took large amounts of chaga powder daily for months. If you have kidney disease or a history of kidney stones, ask your doctor before using it.
- Blood thinners: in animal studies chaga inhibited platelet aggregation, so it may add to the effect of anticoagulant or antiplatelet drugs. Clinical relevance is unknown.
- Diabetes medication: lab studies suggest chaga could add to the blood-sugar-lowering effect of these drugs.
- Pregnancy and breastfeeding: there’s little safety data, so it’s best to avoid it unless your doctor says otherwise.
- Before surgery: tell your care team about any supplements, chaga included.
Trying chaga in a tea blend
If you’re curious about the flavor, a blend is the easiest way to start. Our Chaga Spice Chai combines Assam black tea and chaga with cinnamon, ginger and cardamom, finished with vanilla notes. Brew about 3 g per 12 oz cup at 195°F for 5 minutes, then add milk for a chai latte. It contains caffeine from the black tea. If you prefer a mushroom blend in your coffee mug, our Coffee with Mushrooms Dark Roast uses lion’s mane, cordyceps and reishi (not chaga). Browse more in the tea collection.
Chaga FAQ
Does chaga have caffeine?
Chaga itself isn’t a caffeine source. Blends that include black tea or coffee do contain caffeine, so check the label.
Where does chaga grow?
Mainly on birch trees in cold northern forests. It forms a black, cracked lump on the trunk, usually where the tree was once wounded.
Is chaga the same as reishi?
No. They’re different fungi. Reishi grows as a shiny, shelf-like fruiting body; chaga is a hard conk on birch. Both are bitter and usually brewed or extracted.
Can you forage chaga yourself?
Only if you’re sure of the identification and have permission to harvest. Take a small portion and leave the rest on the tree. When in doubt, buy from a reputable supplier.
Is chaga safe to drink every day?
Because of its oxalate content and possible drug interactions, daily heavy use isn’t a good idea. Keep to label servings and talk to your doctor if you have kidney issues or take medication.
Sources
- Chaga Mushroom, Ting Bao and Jyothirmai Gubili, The ASCO Post, 2019
- Chaga mushroom-induced oxalate nephropathy that clinically manifested as nephrotic syndrome: A case report, PubMed Central
- Development of End Stage Renal Disease after Long-Term Ingestion of Chaga Mushroom: Case Report and Review of Literature, PubMed
Facts checked in October 2026.
This article is for general information only and is not medical advice. If you have a health condition, are pregnant or take medication, ask your doctor before changing your caffeine intake.
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