Hobby gardeners report again and again that they use ash as fertilizer in the garden. But which one is suitable and which plants can be fertilized with it? Here you can find out everything about ash as fertilizer.

wood ash

Wood ash such as chimney ash or ash from burned charcoal is well suited. However, it must be untreated wood that has not been burned with other materials. It is therefore the combustion residue of natural, untreated wood. If you want to use chimney ash, you should not use a chimney lighter and scraps of paper from magazines to light the wood.

plant ash

Plant ash is also suitable. The nutrients it contains are readily available. But only the plant ash that comes from untreated plants may be used.

Unsuitable types of ash

  • Coal and lignite briquettes: contain traces of radioactive substances
  • Wood waste pellets: high heavy metal load
  • Tobacco ash: contains toxic substances

Nourishing ingredients

There are many nutritive substances in wood and plant ash:

  • Phosphoroxid
  • magnesium oxide
  • Potassium oxide
  • calcium oxide

However, most of the nitrogen escapes during the combustion process.

mode of action

Wood and plant ash is considered a fertilizer rich in potassium and lime. Due to the lime, it has a neutralizing effect in acidic soils. In addition, it counteracts rot and fungal infections.

Calcium oxide, also known as burnt lime, dissolves in the water in the soil. This increases the pH value of the soil substrate, the calcium is released and can now be absorbed by the plant roots.

Calcium also serves as an electrical bridge between clay minerals and humus molecules in soils that contain sufficient humus, enabling the formation of stable soil crumbs.

Note: Before you start ash fertilization, it is advisable to carry out a pH test of the soil. If your garden soil is neutral, slightly acidic or already slightly alkaline, you should not fertilize with ash.

application and dosage

Early spring, just before the buds sprout, is an ideal time to start ash fertilization.

  • Apply ash fertilizer only when there is no wind
  • always wear gloves
  • prevent dust formation by humidification
  • water the soil after application
  • do not sprinkle on plant parts to avoid chemical burns

The dosage should be as low as possible in order to avoid over-fertilization and thus damage to the soil and the plants growing in it.

20 to 30 grams of wood or plant ash per square meter are sufficient. After 8 weeks, the application can be repeated if the need persists. You should not exceed the annual dose of 200 to 400 grams per square meter on acidic soil. If you have fertilized regularly in one year, you should not repeat the fertilization for another 3 years at the earliest. Don’t forget the pH test to be absolutely sure whether a new ash fertilization is really necessary.

Advantages and disadvantages


  • longer growing season for deciduous trees
  • prevents potassium deficiency
  • sustainable fertilization
  • less needle shedding in conifers
  • Promotion of soil life
  • good for plants with high mineral requirements


  • partially severe chemical burns of parts of plants when ash gets on plants
  • not suitable as sole fertilizer
  • in the case of over-fertilization, life in the soil is at risk and the plants are severely impaired

Plants that tolerate ash fertilization

  • Vegetables such as tomatoes , leeks, Brussels sprouts, celery, carrots, onions and leeks
  • Perennials such as globe thistle, wild strawberry, woodruff, spurge, cranesbill and coneflower
  • Shrubs such as deutzia, mother-of-pearl, false jasmine and viburnum
  • Fruit trees such as raspberries , gooseberries, currants and grapevines
  • Summer flowers such as fuchsias, geraniums and African daisies

Plants that do not tolerate ash fertilization

Plants that prefer acidic soil and ericaceous plants should not be fertilized with ash.

Tip: Ash is not only a good fertilizer, you can also use it to combat algae, moss and weeds.

frequently asked Questions

Yes, this will speed up the decomposition processes on your compost. Especially with acidic compost. However, you should only add a little of it to your compost to avoid over-calcification.

If you use grill pans that catch the fat, grill ash is also suitable. However, if fat is allowed to drip onto the wood or charcoal when grilling, the high temperatures produce fat degradation products such as acrylamide, which is not healthy for either plants or humans. In addition, you should not use a grill lighter.

Wood ash can be very damaging to soil life in light sandy soils. If the wood ash is not solidified, it will dissolve too quickly, especially if applied before precipitation. This changes the soil chemistry in such a way that the plants in the soil cannot absorb any nutrients for a short time. Growth stops and sensitive plants can die. However, you can reduce the solubility of the wood ash by pelleting it before spreading.

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