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How Wood Vinegar compares
Full guide and scienceWood vinegar concentrate (this bottle)
- Condensed from pyrolysis smoke, so the organic acids and phenols arrive together in one liquid
- Known specific gravity (1.1) and pH range, so a 5 ml/L dilution means the same thing every time
- About two years' shelf life sealed; the acids preserve it
- One bottle covers foliar, drench, seed, fertigation and compost use at set rates
Home-made smoke water
- Smoke bubbled through water, or burnt material soaked; strength depends on the fire, the fuel and the soak
- No way of knowing its strength or pH without testing it
- Mostly used as a one-off soak for hard-to-germinate seed
Made by Growers · Backed by Science
Wood vinegar: a pyroligneous acid biostimulant for soil, foliar, seed and compost use
99.5% Pyroligneous Acid Foliar & Soil Drench Seed Soak & Compost pH 4.5–6.5 500 ml & 1 Litre Packed in Stockport
Wood vinegar is the liquid that condenses out of the smoke when plant biomass is heated without oxygen to make biochar. Chemists call it pyroligneous acid, or wood acid. It is mostly water carrying more than 200 organic compounds, chiefly acetic acid and lignin-derived phenols. Diluted and applied to leaves, soil, seed or a compost heap, it works as a plant biostimulant and carries negligible NPK. The Dr Forest bottle is a 99.5% pyroligneous acid concentrate with a 0.5% organic carbon fraction, for UK gardens and allotments.
It goes a long way. At the standard 5 ml per litre foliar rate a 500 ml bottle makes 100 litres of spray, ten full 10 litre watering cans, and the 1 litre bottle makes 200 litres. The concentrate is mildly acidic (pH 4.5–6.5) and must always be diluted. It sits alongside your normal feeding and helps the soil biology turn that feed into something the plant can use.
99.5%Pyroligneous acid
200+Organic compounds
+21%Mean yield, 65 studies
5 ml/LFoliar rate
What wood vinegar is used for in the garden
- Foliar spray — 5 ml per litre every 3–4 weeks; rice and rapeseed trials report more chlorophyll and higher yield
- Soil drench — 5–10 ml per litre to the root zone; the organic acids are a quick carbon meal for soil microbes, whose enzymes release nutrients from organic matter
- Making fertiliser go further — drenched 2–3 days after an organic feed, it feeds the microbes that break the feed's organic nitrogen and phosphorus down into plant-available forms
- Seed soak — diluted 1:100 as a 6–24 hour soak before sowing, or sprayed over the drill as you sow
- Compost accelerant — 10 ml per litre of water on the heap, where the acids help hold nitrogen in the compost
- Fruit quality — in a greenhouse tomato trial, a dilute pyroligneous acid drench gave more fruit, with more vitamin C and carotenoids
Why a pyrolysis condensate rather than home-made smoke water?
Wood vinegar concentrate (this bottle)
- Condensed from pyrolysis smoke, so the organic acids and phenols arrive together in one liquid
- Known specific gravity (1.1) and pH range, so a 5 ml/L dilution means the same thing every time
- About two years' shelf life sealed; the acids preserve it
- One bottle covers foliar, drench, seed, fertigation and compost use at set rates
Home-made smoke water
- Smoke bubbled through water, or burnt material soaked; strength depends on the fire, the fuel and the soak
- No way of knowing its strength or pH without testing it
- Mostly used as a one-off soak for hard-to-germinate seed
Dr Forest, Stockport
Dr Forest is a small science-led fertiliser business in Stockport, Greater Manchester, founded in 2020. Wood vinegar is plant-derived, and it suits a no-dig or living-soil approach where the aim is to feed the soil biology. If that idea is new to you, start with What is living soil? Made by Growers. Backed by Science.
The Science
The science of pyroligneous acid: smoke chemistry, soil biology and dose
What pyrolysis produces
Heat plant material to a few hundred degrees with the air shut out and it breaks apart without burning. The solid left behind is biochar; the gases are cooled, and the part that condenses is pyroligneous acid, better known as wood vinegar. Theapparat et al. (2018) describe it as 80–90% water with more than 200 organic compounds in the remainder, the largest single one being acetic acid, followed by other short-chain acids and a family of lignin-derived phenols such as guaiacol and syringol.
None of those compounds is in the wood to begin with. The heat makes them from cellulose, hemicellulose and lignin, which is why wood vinegar smells of smoke. Biochar is the long-term soil carbon from that process; wood vinegar is the short-lived liquid side of it. For the seaweed side of the biostimulant story, see What is seaweed fertiliser?
Typical analysis
| Property | Value | Note |
|---|---|---|
| Pyroligneous acid (wood vinegar) | 99.5% | Mostly water carrying organic acids, phenols, esters and ketones |
| Organic carbon concentrate | 0.5% | Fine biochar fraction, settles on standing; shake before use |
| pH | 4.5–6.5 | Mildly acidic concentrate |
| EC (conductivity) | 10–18 mS/cm | Undiluted |
| Specific gravity | 1.1 | 5 ml weighs about 5.5 g |
| NPK | Negligible | Use alongside a feed |
Leifeld and Walz (2025) found a mean pH of 3.5 in the 26 studies that reported it; this one sits one to three units higher, so it is less acidic at the same dilution. It still needs gloves neat and dilution before it goes near a plant.
Across 65 studies, the gains peaked at half a per cent to one per cent.
Mechanisms of action
01
Karrikins: a smoke signal, unproven in wood vinegar
Flematti et al. (2004, Science) isolated a butenolide from plant- and cellulose-derived smoke that promoted germination in a number of species at a level similar to plant-derived smoke-water; the family was later named karrikins. Kochanek et al. (2016, PLOS ONE) found karrikinolide in biochar and, at 69 ng/ml (460 nM), in the water used to scrub the gas from a slow-pyrolysis unit. That liquid took dormant seed from 0–8% germination on water to as much as 91–96%. The authors class it separately from wood vinegar, though, and how much karrikin a given wood vinegar carries is uncertain. This batch has not been assayed, so we make no karrikin claim for it.
02
Organic acids feed the soil and wake its enzymes
Acetic and butyric acids are about the simplest carbon a soil microbe can eat. Yang et al. (2024, Plants) drip-applied wood vinegar to pots of saline soil growing cotton and recorded soil urease activity 96.85% higher than the untreated control at the stronger dose, with β-glucosidase activity also up. Seok and Park (2024, Environmental Science and Pollution Research) found basal soil respiration rose and soil nitrate fell where wood vinegar was added to a urea-fertilised soil. A pot trial and a laboratory study respectively, so read across to a Stockport allotment with care, but the direction is consistent.
03
Leaf sprays: more chlorophyll, more crop
Hur et al. (2025, Plant Physiology and Biochemistry) sprayed rice with wood vinegar at three growth stages and recorded a higher photosynthetic rate, more chlorophyll, total soluble sugars of 9.71 mg/g and a yield lift of up to 32.4%. Zhu et al. (2021, Agronomy) sprayed rapeseed twice at a 400-fold dilution and averaged 9.58% more seed yield, with leaf area index up 23.45%. The rice figure is the best of several spray timings; the rapeseed figure is a two-year average.
04
Dose: a narrow window
Leifeld and Walz (2025, Agronomy) reviewed 65 studies. Wood vinegar raised yield by an average of 21% and biomass by 25%, with the optimum at around 0.5–1%. Sprayed on leaves, yields fell above about 6%; as a drench, above about 11%. Ofoe et al. (2022, Plants) saw the same curve in tomato: a fortnightly 0.5% drench gave about 26% more fruit weight and 66% more fruits, while 2% reduced growth and yield. The Dr Forest rates of 5 ml/L (0.5%) foliar and 5–10 ml/L (0.5–1%) drench sit inside that window. Stick to them.
05
Holding nitrogen in the compost heap
Liu et al. (2023, Agriculture) added bamboo vinegar, the same class of pyroligneous acid made from bamboo, to a compost of tomato residues and duck manure and cut ammonia emissions by 25%, with total nitrogen loss down by up to 7.2% in the early phase. The acids stop the heap's pH climbing, which keeps more nitrogen as ammonium instead of letting it leave as ammonia gas.
Where the evidence is thin
Three caveats. This batch has not been assayed for karrikins, and whether wood vinegar carries them in useful amounts is uncertain (mechanism 01). The Leifeld and Walz review found soil organic matter up a modest 9% but no significant rise in soil microbial biomass, so mechanism 02 is evidence of busier enzymes; whether there are more microbes is unproven. And the trials in that review ran for one or two growing cycles, seven months on average; we know of no controlled trial on a British allotment. We think the mechanisms transfer. We are not going to promise a percentage.
Scientific references
- Flematti, G.R., Ghisalberti, E.L., Dixon, K.W. and Trengove, R.D. (2004). A compound from smoke that promotes seed germination. Science, 305(5686), 977. doi:10.1126/science.1099944
- Kochanek, J., Long, R.L., Lisle, A.T. and Flematti, G.R. (2016). Karrikins identified in biochars indicate post-fire chemical cues can influence community diversity and plant development. PLOS ONE, 11(8), e0161234. doi:10.1371/journal.pone.0161234
- Theapparat, Y., Chandumpai, A. and Faroongsarng, D. (2018). Physicochemistry and utilization of wood vinegar from carbonization of tropical biomass waste. In P. Sudarshana, M. Nageswara-Rao and J.R. Soneji (eds), Tropical Forests: New Edition. IntechOpen. doi:10.5772/intechopen.77380
- Leifeld, J. and Walz, I. (2025). Pyroligneous acid effects on crop yield and soil organic matter in agriculture: a review. Agronomy, 15(4), 927. doi:10.3390/agronomy15040927
- Hur, G., Ashraf, M., Nadeem, M.Y., Rehman, R.S., Thwin, H.M., Shakoor, K., Seleiman, M.F., Alotaibi, M. and Yuan, B.-Z. (2025). Exogenous application of wood vinegar improves rice yield and quality by elevating photosynthetic efficiency and enhancing the accumulation of total soluble sugars. Plant Physiology and Biochemistry, 218, 109306. doi:10.1016/j.plaphy.2024.109306
- Zhu, K., Gu, S., Liu, J., Luo, T., Khan, Z., Zhang, K. and Hu, L. (2021). Wood vinegar as a complex growth regulator promotes the growth, yield, and quality of rapeseed. Agronomy, 11(3), 510. doi:10.3390/agronomy11030510
- Ofoe, R., Qin, D., Gunupuru, L.R., Thomas, R.H. and Abbey, L. (2022). Effect of pyroligneous acid on the productivity and nutritional quality of greenhouse tomato. Plants, 11(13), 1650. doi:10.3390/plants11131650
- Yang, L., Tang, G., Xu, W., Zhang, Y., Ning, S., Yu, P., Zhu, J., Wu, Q. and Yu, P. (2024). Effect of combined application of wood vinegar solution and biochar on saline soil properties and cotton stress tolerance. Plants, 13(17), 2427. doi:10.3390/plants13172427
- Seok, Y.J. and Park, J.H. (2024). Reducing nitrogen leaching using wood vinegar treated in urea-fertilized soil. Environmental Science and Pollution Research, 31(5), 7138–7145. doi:10.1007/s11356-023-31517-1
- Liu, C., Lin, Y., Ye, J., Price, G.W. and Wang, Y. (2023). Effect of bamboo vinegar on control of nitrogen loss in vegetable waste and manure composting. Agriculture, 13(7), 1331. doi:10.3390/agriculture13071331
Figures describe the published literature on pyroligneous acid and are not product-specific yield guarantees.
How to Use
How to use wood vinegar: foliar spray, soil drench, seed soak and compost
Concentrated — always dilute before use
This is a concentrated liquid (99.5% pyroligneous acid, SG 1.1, pH 4.5–6.5). Never apply undiluted. Dilute according to the rates below before all applications. Agitate well during mixing and application; the fine biochar fraction settles if left standing. Shake the bottle before measuring. A 5 ml measure is one standard teaspoon; a 10 litre watering can at 5 ml/L takes 50 ml.
A biostimulant, not a fertiliser
Wood vinegar carries negligible NPK and works alongside a feed. The research is clear that more is not better: across 65 studies the best results came at 0.5–1%, and in a tomato trial a 2% drench reduced growth and yield. Stay at the rates below.
Application rates
Foliar spray
Mix 5 ml of concentrate per litre of water and apply as a fine foliar spray to both upper and lower leaf surfaces. Apply in the early morning or late evening to avoid rapid evaporation and maximise leaf absorption. The organic acids and phenolics are taken in through stomata and cuticle. Compatible with most organic fertiliser sprays and can be tank-mixed with Dr Forest Seaweed Powder liquid feed for a combined biostimulant and nutrient application.
Soil drench — root zone application
Mix 5–10 ml per litre and apply to the root zone with a watering can. Water thoroughly before and after application to distribute the liquid through the root zone. The organic acids and the carbon fraction stimulate microbial activity in the rhizosphere, increasing enzyme production and nutrient cycling. Particularly effective 2–3 days after applying organic fertiliser, when the extra microbial activity speeds the biological breakdown of the fertiliser's organic nutrients.
Seed treatment
Dilute the concentrate at 1:100 in water and soak seeds before sowing. For direct sowing, spray the diluted solution over the seed drill before covering.
Fertigation — drip, irrigation or liquid feed systems
Add to irrigation water or liquid feed systems at 5 ml/L. Agitate well, as the fine particles can settle in standing solution. Strain through a fine mesh if using with drip emitters. Fully compatible with organic liquid fertiliser programmes.
Compost accelerant
Dilute 10 ml per litre of water and apply to compost during construction or as part of routine watering. A standard watering can (10 litres) needs 100 ml of concentrate. The organic acids fuel microbial activity and speed decomposition. The mildly acidic pH helps maintain the acid conditions that suit early-stage composting and slows the pH rise that drives ammonia loss, conserving nitrogen in the finished compost.
Step-by-step foliar application
- Shake the bottle well. The fine biochar fraction settles during storage. Agitate thoroughly before measuring to get an even suspension.
- Measure and dilute. Add 5 ml of concentrate per litre of water. Stir or shake the spray vessel well to distribute the particles evenly.
- Spray in early morning or late evening. Avoid spraying in full sun, when the stomata close and the liquid evaporates before absorption. Cool conditions with open stomata maximise uptake.
- Cover both leaf surfaces. Apply as a fine mist to upper and lower leaf surfaces. The underside of the leaf has a higher stomatal density and takes the solution in more efficiently.
- Repeat every 3–4 weeks. The biostimulant effect is cumulative; regular applications keep the microbial stimulation going through the growing season.
Safety precautions
This is a concentrated acidic liquid (pH 4.5–6.5). Avoid contact with eyes and skin. Wear gloves when handling the concentrate. Keep out of reach of children. If contact with eyes occurs, rinse immediately with plenty of water. If swallowed, seek medical advice. Once diluted to the recommended rates, the solution is safe for plants, soil and edible crops.
Works well combined with…
Use as a foliar spray alongside Dr Forest Seaweed Powder for a combined biostimulant and trace mineral application. Apply as a soil drench 2–3 days after top dressing with Dr Forest granular fertilisers such as All Purpose 4-4-4, so the microbial lift lands on fresh organic nutrients. Add to Molasses-based compost tea brews for a wider mix of microbial foods. Combine with Humic Acid soil drenches, where the humic acid chelates the minerals released by the extra microbial activity. Use as a seed soak before sowing alongside Mycorrhizal Fungi powder dusted into the seed drill.
Storage
Store in a cool, dry place away from direct sunlight with the cap tightly sealed. The organic acids act as a natural preservative; shelf life is approximately 2 years stored correctly. Do not freeze.
Questions & Answers
Frequently asked questions about wood vinegar
Wood vinegar, also called pyroligneous acid or wood acid, is the liquid that condenses from the smoke when plant biomass is heated without oxygen to make biochar. It is mostly water with more than 200 organic compounds dissolved in it, mainly acetic acid and other short-chain acids, with lignin-derived phenols. It is not a kitchen vinegar. Farmers in Asia have used it for generations.
Always diluted. The standard rates are 5 ml per litre as a foliar spray every 3–4 weeks, 5–10 ml per litre as a soil drench every 3–4 weeks, 1:100 as a seed soak for 6–24 hours and 10 ml per litre on a compost heap. Spray early or late in the day, cover both sides of the leaf, and shake the bottle first because the carbon fraction settles. See the How to Use tab.
No. It carries negligible nitrogen, phosphorus or potassium. It is a biostimulant: it feeds soil microbes with simple organic acids and helps the soil biology break your fertiliser down into plant-available forms. Use it alongside a feed such as All Purpose 4-4-4 or a liquid seaweed programme.
It may, but that has not been established. Karrikins are a small family of butenolide molecules made when plant material burns or is pyrolysed. They were identified in 2004 by researchers in Western Australia studying germination after bushfire, and dormant seed of many species germinates in response to them. They have been measured in biochar and in the water used to scrub the gas from a slow-pyrolysis unit, but the researchers class that liquid separately from wood vinegar. We have not assayed this batch, so we make no karrikin claim for it.
No, but they come from the same process. Biochar is the solid carbon left after pyrolysis, a long-term soil amendment. Wood vinegar is the liquid condensed from the smoke. This bottle is 99.5% pyroligneous acid with a 0.5% fine biochar fraction suspended in it, which is why it settles.
Yes, once diluted to the recommended rates: the solution is safe for plants, soil and edible crops. The concentrate is mildly acidic (pH 4.5–6.5), so wear gloves when handling it, keep the bottle out of reach of children and pets, and rinse any eye contact with plenty of water.
Yes, with most organic liquid feeds. It tank-mixes with seaweed extract, humic acid and liquid fertiliser solutions; test a new combination on a small area first. Do not mix with strongly alkaline products, which react with the acids.
It is made from plant biomass by pyrolysis and fits organic and no-dig gardening. We make no organic certification claim for it.
The fine biochar carbon fraction settles during storage. That is normal and does not mean the product has gone off. Shake well before each use, and strain through a fine mesh after diluting if your sprayer has fine nozzles. Stored cool, dark and sealed it keeps for about 2 years; the organic acids preserve it. Do not freeze.
At the 5 ml per litre foliar rate, a 500 ml bottle makes 100 litres of spray, ten 10 litre watering cans, and a 1 litre bottle makes 200 litres. At the 10 ml per litre compost rate, the two sizes make 50 and 100 litres.
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