Again and again, ideas for recycling household waste in allotment gardens make the rounds. Coffee grounds, eggshells and banana peels have long been used by gardeners to improve the soil. Are wood ash or barbecue ash also suitable as fertilizer?
In a nutshell
- Wood ash consists mainly of calcium, magnesium, potassium and other trace elements
- the origin and treatment of the wood are decisive
- Wood ash affects pH
- As fertilizer, wood and barbecue ash are only suitable to a limited extent
components of the wood ash
Wood consists mostly of carbon and water. When you burn it, carbon dioxide and water vapor are produced. Both escape into the atmosphere. The mineral components remain. The ashes of the wood contain residues of the nutrients that the tree has absorbed from the soil during its lifetime.
The most important ingredients are:
- calcium
- magnesium
- potassium
- iron
- boron
- sodium
- phosphorus
- manganese
The origin of the burned wood is decisive for the further use of the ash. Depending on how you used the wood before burning it can contain heavy metals such as lead, cadmium and chromium.
This wood ash belongs in the residual waste bin, not as a supposed fertilizer in the garden!
barbecue ash
- You rarely know the origin and nature of the wood from which the charcoal was made.
- Harmful substances are often used to light the charcoal.
- The fat dripping onto the charcoal leads to the formation of acrylamide. This is harmful to health.
These aspects mean that the use of barbecue ash as fertilizer in kitchen gardens is not recommended.
Harmless wood
If you fell a tree on your property, cut it up, lay it out to dry and burn it in the oven without any other ingredients, you can use the ashes for fertilizer. Note the high calcium oxide content of the ash. Calcium oxide is known as quicklime. Applying the ash fertilizer can burn the leaves. It can also cause damage to microorganisms in the soil.
Anyone who cares for the garden soil with ash must also pay attention to the pH value. The ash has a pH between 8 and 11. Only unplanted heavy clay or loam soils benefit from ash fertilization. This should be avoided on all other soils and on planted beds.
Notice: Fertilizing acidic soils with small amounts of wood ash can help strengthen plants and increase their resistance to pests.
Tips for safe use
- Only spread ashes from untreated wood in the garden.
- Wood that you have treated with paint or oil can contain harmful substances. It doesn't belong in the oven and its ashes don't belong on the beds.
- Only use the ash to fertilize suitable ornamental plants and lawns.
- Some plants cannot tolerate the high lime content.
- Use only small amounts of wood ash fertilizer.
- Fertilize suitable areas every four to six weeks.
Tip: Ash helps kill weeds. It puts an end to mosses, algae and root weeds.
frequently asked Questions
Can wood & barbecue ashes be disposed of on the compost?Barbecue ash does not belong on the beds or on the compost. Wood ash from untreated wood should only be added to the compost heap if the compost is intended exclusively for ornamental plants. Spread the ashes very sparingly.
Does the ash change if paper is burned at the same time?If you use blank paper or toilet paper rolls for kindling, the composition of the ashes changes little. If you burn brightly printed paper, the ashes must not get on the beds.
How much ash is put on the beds for fertilization?Spread about 1 cup of ash per square foot of bare area. It is also possible to mix them into the irrigation water.
Wood ash fertilization is suitable for loamy or clayey soils before reseeding.
Ornamental plants that need alkaline soils can be strengthened by fertilizing with wood ash. These include: roses, phlox, lavender, carnations, geraniums, gladioli.
Can potted plants be fertilized with wood ash?Potted plants can be fertilized. However, special care should be taken to prevent over-fertilization. A few weeks before planting, mix the ash with potting soil and sand and add the mixture to the bucket. Use the ashes sparingly.