It makes sense to spread the ashes from the stove in your own garden. This reduces waste and the natural product ash gets a new meaning. In order for it to pass as a natural product, various requirements must be met.

Ash has a basic effect and should be used with caution

Table of Contents

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  1. the essentials in brief
  2. Suitability of ash fertilizer
  3. Different types of ash
  4. areas of application
  5. Ash fertilization problems
  6. frequently asked Questions

    7. the essentials in brief

    • Ash contains lime, potassium, iron and phosphate and is strongly basic with a pH of 11 to 13.
    • Ash fertilizer is mainly used for liming acidic soils.
    • Only ashes from pure wood without heavy metals should be used, i.e. wood whose origin you know. Ashes from barbecue charcoal, lignite or hard coal and briquettes should not be used as fertilizer.
    • If there is a potassium deficiency, some plants tolerate fertilization with pure ash.

    Is ash suitable as fertilizer?

    Ash is a natural fertilizer that is easy to make. Any hobby gardener can make it with a wood or fireplace stove. Ash is rich in lime and potassium. It also contains iron and phosphate, which are essential for healthy and vigorous plant growth. Ash fertilizer is mainly used for liming acidic soils. Since ash with a pH value between 11.0 and 13.0 has a strong alkaline effect, it should not be used without restriction for all plants.

    Wood ash contains:

    • 25 to 45 percent burnt lime (calcium oxide)
    • three to six percent magnesium and potassium oxide
    • two to six percent phosphorus pentoxide
    • mineral trace elements (iron, manganese, boron and sodium)
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    What ash can I use?

    Not every ash should be used to fertilize the plants. Fireplace ash from wood or burnt charcoal is suitable, but you should also know exactly where the wood comes from. Both deciduous and softwoods are processed into charcoal. This can be loaded differently depending on the source.

    digression

    charcoal

    The solid fuel is formed when air-dried wood is heated up in the absence of oxygen. At various stages of heating, gases escape and eventually charring occurs. During these processes, temperatures between 150 and 500 degrees Celsius are reached. Good charcoal shines black, whereby the structure of the wood is still clearly recognizable. Poorly charred coals, on the other hand, have a red to brown-red colour. During the production of these so-called red coals, temperatures of 300 degrees Celsius are not exceeded.

    You should pay attention to this

    When additives in wood are burned, harmful substances can be produced and left in the ash, poisoning the soil. It may contain dioxin or other toxic substances. If the wood comes from an industrial region or near a motorway, it can be contaminated with heavy metals.

    To make flawless wood ash:

    • burn untreated and natural wood
    • Use wood without varnish and glaze (66.50€).
    • Use dry branches, leaves or nut shells to light

    Do not use brightly printed newspaper for lighting, as these contain chemical substances and can contaminate the ashes. Even black and white newspaper, egg boxes or toilet paper rolls should not be used. The material is often made from recycled paper, which can be contaminated with mineral oil components from colorful brochures. Also, be careful not to mix wood ash with charcoal ash.

    Unsuitable ash

    Ash from coal briquettes should not be used as fertilizer

    Depending on the origin of the wood, the ash can contain harmful heavy metals that also poison the soil and plants. Lead, cadmium or chromium can often be detected in critical concentrations. Ash produced from lignite and hard coal or coal briquettes is also unsuitable as a natural fertilizer due to the heavy metal contamination.

    Wood naturally contains heavy metals because the tree absorbs substances from the environment as it grows. The toxic metals also come from tool wear during production by logging machines.

    To be on the safe side, you should dispose of the remains of burnt charcoal in the household waste, because here the origin is often unknown. In addition, ash from the grill contains fat residues that have arisen during burning. Decomposition products such as acrylamide are harmful to health and are lost in the soil just as little as cigarette ash.

    origin disadvantage
    pellets wood waste high heavy metal load
    briquettes lignite or hard coal contains traces of radioactive elements
    tobacco leaves of the tobacco plant toxic soot and heavy metals, hardly any nutrients
    money fossil plant remains contains heavy metals and radioactive substances

    Where can I use ash fertilizer?

    If you can ensure that your ashes are clean, you can use the natural product in many ways in the garden. It improves the lawn and can be distributed in beds and under shrubs. You also benefit from positive side effects.

    This causes ash fertilization:

    • eliminates moss and algae growth
    • kills root weeds
    • disinfects open wounds

    Only use wood ash that is flawless. Otherwise you risk that toxic substances are absorbed by crops.

    Which plants tolerate ash?

    Ash prevents potassium deficiency. In small amounts, you can fertilize various plants with pure ash. The particles are washed into the ground by rain and dissolve within a short time. This means that the substances are quickly available to plants. Bog plants and plants that prefer acidic soil should not be supplied with ash.

    Particularly suitable plants:

    • vegetable garden: Tomatoes, Brussels sprouts, leeks
    • perennials and shrubs: roses, gladioli, phlox
    • flower beds: geraniums, fuchsias
    • fruit trees: grapevines, gooseberries, raspberries
    • indoor plants: all lime-tolerant plants

    Fruit trees are happy about a good portion of ash

    tips

    In principle, you can also fertilize potatoes with ash. However, caution is advised, because ash fertilization promotes potato scab.

    In the forest

    If you own your own forest, you will appreciate the high lime content of the wood ash. The majority of all German forest soils are too acidic. In a well-dosed concentration, wood ash can contribute to improving the soil in the long term. As a result, the trees can root deeper, increasing their stability.

    Advantages of ash fertilization:

    • Extension of the growing season in deciduous trees
    • reduced needle drop in conifers
    • increased fine root formation in the topsoil

    Ash fertilization problems

    If ash is applied in too high concentrations or in unfavorable weather, there can be negative consequences. These affect both soil life and plants. Incorrect fertilization can cause a lot of damage, so you should use ash in low concentrations.

    crop damage

    The high content of calcium, which is present as burnt lime in its most aggressive form, causes liming of the soil. This highly alkaline quicklime can cause leaf burns if residue is left on plants. In agriculture, calcium oxide is only distributed on unvegetated areas that have a loamy to clayey subsoil.

    piñata

    Another problem is the often unknown composition of the various substances in wood ash. The proportion of minerals can vary greatly, just like the heavy metal content. Fertilization tailored to the soil is not possible without a precise analysis of the ash. You run the risk of enriching the earth with more toxic substances than improving it.

    soil damage

    If burnt lime is spread on light sandy soils, it can cause massive damage to soil life due to its low buffering capacity. Wood ash that has not solidified dissolves particularly quickly if precipitation occurs after application. This can change the soil chemistry so that the plants growing there can no longer absorb nutrients in the short term. Their growth stagnates and sensitive plants can die. To reduce solubility and give you better control over changes in soil pH, the ash should be pelleted before application.

    tips

    Allow wood ash to swell in water so that the fine-grained particles become soaked. Then place the pot on the stove and wait for clumps of ash to form. These resolve more slowly.

    Have ash tested

    If you want to be on the safe side, you can have your ashes analyzed in a laboratory. There are quantitative tests that check the ash for ten to twelve common heavy metals. Ten grams of wood ash are sufficient for a precise analysis.

    If you burn different types of trees, you can send in the ashes as a mixed sample. However, it is then not possible to allocate the ingredients to the respective ash. If you send in several samples, you have to reckon with higher costs. Depending on the laboratory, a test costs between 100 and 150 euros.

    frequently asked Questions

    Is ash suitable for plants that prefer acidic soil?

    Ash increases soil pH and should only be used on plants that prefer calcareous soil. Hydrangeas, ferns, rhododendrons or peonies like a rather acidic humus soil, which is why ash is not suitable as a fertilizer. You can fertilize these plants with coffee grounds instead.

    How do I fertilize with ash?

    Choose a windless day so that the dusty ash does not spread in the garden. To be on the safe side, you can moisten the ashes a little. The high pH can damage the skin, so you should wear gloves. After application, the soil is watered. Ash should never be mixed with fertilizers containing ammonium, such as manure or manure, as gaseous ammonia can form. Also avoid mixing ash with phosphate. In the process, calcium phosphates that are difficult to dissolve and not available to plants can develop.

    How much ash should I use for fertilizing?

    For liming and soil improvement, you can fertilize soil with ash every three to four years. For heavy soils with a pH of 4.0, 200 to 400 grams per square meter are sufficient. For less acidic soils, reduce the amount to 100 to 200 grams. Light soils can quickly become overlimed and should therefore not be fertilized with ash. Here, ground eggshells will do.

    Can I put ash on the compost?

    Many microorganisms become more active at high pH. Adding ash can accelerate the decomposition processes on the compost, especially if the compost is acidic. However, you should only sprinkle the ash on the compost in small amounts to avoid over-liming. If you are unsure of the source of the wood ash, you should dispose of it in the household waste due to possible contamination.

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Garden design