Use stone flour in the garden

Use stone flour in the garden

the essentials in brief

  • Stone powder is very finely ground rock.
  • Depending on the intended use, you use different types.
  • Stone meal from volcanic rock is suitable for soil improvement as well as for compost production.
  • Other varieties can be used to combat fungal diseases and pests.

What is stone meal?

Rock powder or rock flour (€ 14.95 at Amazon *) is exactly what its name says: very finely ground rock. However, not just any rock is used, because depending on the intended purpose, different types of stone with different properties are used. Rock types such as

  • Basalt (and other volcanic rocks)
  • Diabase
  • granite
  • limestone
  • Clay minerals (bentonite)
  • or zeolite

also read

  • Use primary rock flour correctly
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  • Apply effective microorganisms in the garden

Use, because they can be used very well in the garden due to the high content of minerals and trace elements. The soil-improving properties of clay, volcanic rock or marl were already known in ancient times. According to German law, stone meal is not considered a fertilizer, but is classified as a soil additive.


Is there a difference between rock powder and primary rock?

In fact, there is a major difference between rock powder and primary rock powder. The latter consists of rocks of volcanic origin that contain a high proportion of valuable minerals and trace elements such as calcium, iron and magnesium and are therefore perfect for use in the garden. Primary rock flour improves the soil, promotes humus formation and ensures better water storage capacity. Stone powder, in turn, can also consist of other types of stone with completely different properties, for example clay minerals.

Possible applications

rock flour

Depending on the type of rock used, rock powder can be used for very different purposes. The fine powder is particularly often used to improve the garden soil and its structure, it is also used to control pests and diseases on plants, to produce plant manure and compost and for construction work.

Stone meal as a soil improver

“Primary rock meal is not a fertilizer, but a soil additive. As a result, it is not suitable for correcting nutrient deficiencies! "

For the purpose of soil improvement, you should use primary rock powder, as only rocks of volcanic origin have the necessary proportions of minerals and trace elements. Even if this stone meal is rich in iron, magnesium and calcium, it is not considered a fertilizer - the reason for this classification is the lack of or only a small amount of the main nutrients nitrogen, phosphorus and potassium. Nevertheless, the use of primary rock flour as a soil additive offers a whole range of advantages for garden soil and plants:

  • Increase in water storage capacity: Sandy soils in particular benefit from enrichment with clay flour, as this improves the water storage capacity of these very permeable subsoils.
  • Improvement of the soil life : The minerals and trace elements contained in the rock powder are immediately available to soil organisms, so that they contribute directly to the formation of humus. The higher humus content, in turn, uses vegetables and other garden plants without these being threatened by possible overfertilization.
  • Increase in soil fertility : Rock flour contains many important minerals and trace elements that are enriched directly in the garden soil and thus increase its quality. At the same time, the soil structure becomes more crumbly and loose. In addition, depending on the type of rock used, stone powder is suitable for improving a pH value that is too low.
  • Slow plant availability: As the stone meal has to weather completely before the plants can absorb the nutrients it contains, there is no risk of over-fertilization - instead, it is slowly and very gradually released to the plants.

Suitable stone meal types

There are different primary rock powders that consist of different parent rocks. In this table, we have clearly compiled for you which rock flour is best used for in the garden.

Types of primary rock meals
Parent rockMain ingredientsPossible areas of application
basaltIron, magnesium, other minerals and trace elementsSupply of minerals and trace elements, increase of soil life in the garden soil and in the compost
DiabaseIron, magnesium, other minerals and trace elements, especially calciumSupply of minerals and trace elements, increase of soil life in garden soil and in compost, lowering of the pH value of excessively alkaline soils
granitelower mineral contentIncrease in soil life in garden soil and in compost, lowering the pH value of excessively alkaline soils
BentoniteClay mineralsImprovement of the water storage capacity, improvement of the ratio of clay and humus, especially for sandy soils
Zeolitelower mineral contentImprovement of the water storage capacity, strongly alkaline effect


You should use lava flour when caring for strongly consuming plants such as tomatoes and lawns. This contains the highest proportion of micronutrients and is therefore particularly suitable for this purpose.


How you dose the rock flour depends on various factors. Above all, the composition of the garden soil and its pH value as well as the specifically selected product determine how much of the material you should or may apply. You should therefore carefully study the manufacturer's recommendation and be sure to measure the pH of your garden soil before using it. In order for a noticeable effect to occur, the material has to be applied regularly - mostly annually - a one or two application usually does not show any noticeable success.


rock flour

Rock flour can either be scattered and worked into the soil or dissolved in liquids (such as irrigation water or plant manure) and applied in this way. The material is also very suitable for stimulating the microbial life in the compost and thus accelerating the decomposition of the organic material - quite apart from the fact that the nutrients contained in stone meal are also added to the compost and thus enrich it with minerals.

You can apply primary rock flour in three ways:

  • Sprinkle directly dry on the ground (e.g. between rows of vegetables)
  • work into the soil (e.g. when digging up, when planting)
  • Dissolve in water or plant manure and water the plants

To work the rock flour into the ground, do the following:

  1. Choose a windless, dry day in spring or late autumn.
  2. Moisten the soil well beforehand so that the fine flour does not blow away.
  3. Spread the rock flour directly on the beds.
  4. Wear mouth and respiratory protection!
  5. Work the material into the ground with a hoe.
  6. The stone meal should be worked into the soil about three to five centimeters deep, as this is where it is best absorbed by the roots.

During the growing season you only add the stone meal to the irrigation water or to a plant manure you have prepared yourself. The latter also has the advantage that the brew smells less intense - the material binds the unpleasant smell.


How do I know what pH my garden soil has?

You can determine the pH value of the garden soil with a simple test from the pharmacy or garden specialist. To do this, you need test strips that you hold in a soil sample mixed with a little water (it is essential to follow the manufacturer's instructions!). Based on their discoloration, you can then tell whether the soil is alkaline (basic) or acidic. Then select the appropriate rock flour to neutralize the respective acidity.

Plant protection

However, stone meal is not only suitable for soil improvement, but can also be used in pesticides to combat pests and fungal diseases. Species of rock rich in silica, such as granite, are predestined for this purpose and ward off attackers from both animal and fungal species.


But be careful! Some plants do not tolerate stone meal. Above all, this includes plants with a preference for acidic soils such as hydrangeas, rhododendrons and azaleas, camellias and blueberry bushes.

Against fungal diseases

rock flour

Silicic acid strengthens the plant tissue and makes it less susceptible to the penetration of fungal pathogens. To ensure that your plants benefit from this property, prepare a spray mixture from granite or another stone meal containing silica:

  1. Mix 200 grams of stone flour with a little water.
  2. Gradually dilute the mixture with ten liters of water.
  3. Fill the spray into a spray device.
  4. Spray endangered plants once a week.
  5. Spray on an overcast day or early in the morning

If you do not use the entire amount right away, you can keep the rest until the next use. Then, however, the spray mixture should first be stirred thoroughly, as the stone dust settles.

Against pests

If you have problems with pests such as lice, spider mites (red spider), thrips, etc., it helps to regularly powder the plants in question with stone meal. The fine dust prevents the insects from breathing and moving, which is why the little animals quickly disappear. Apply the stone meal dry to the plants, for example with the help of a powder syringe or a hand brush (dip a hand brush in the flour and then shake it out over the plants). The best time of day to do this is early in the morning, when the plants are still damp from the dew. Incidentally, rock flour is particularly suitable as a preventive agent against the notorious box tree moth.

Against snails

Snails are probably the biggest nuisance in any garden. The voracious creatures can often only be kept from eating the lettuce and other delicious vegetables and ornamental plants with great difficulty. With a five to ten centimeter wide, thick protective ring made of stone dust, you can keep snails away from your garden plants and at the same time ensure that the soil and vegetation receive an extra portion of minerals. On the other hand, an odor-intensive paste made of stone meal and crushed garlic and chopped onions, which you bring into the rodents' passages, should help against voles.

Against weeds in joints


Joints between pavement slabs or patio tiles tend to overgrown with weeds quickly. If you don't want to pull out cheeky weeds all the time, you have no choice but to close these gaps tightly. However, many grout - for example silicone - do not allow rainwater to seep through. If, on the other hand, you fill it with rock flour, the joints are sealed against weeds and still let water through. The fine-grained material fills even the smallest of cavities, and it also lowers the pH value at the area treated with it - so weeds don't stand a chance.

However, do not use any rock meal for this purpose, but rather granite meal that is as low in nutrients as possible. This type of stone contains only a few minerals that promote growth and is also prepared by some manufacturers (such as Dansand) as a grout. Stone powder for grouting is available in different colors to match the color of the terrace tiles or paving stones.

Where can I get stone flour?

You can basically get rock flour in every DIY store and garden center, and discounters also have cheap offers from time to time. However, before you access it, read the table of contents first. Not every rock powder is suitable for every purpose and the cheap discount store offers in particular often mainly contain sand-lime brick or granite - both of which are useless for soil improvement, for example. If you are looking for primary rock powder in particular, you should be particularly careful: Since this name is not protected by law, high-quality lava rock is not always used for it.

frequently asked Questions

Is stone meal poisonous?

No, stone meal is not poisonous. There are even varieties that are suitable for human consumption (and are supposed to serve health, but is that really true?). However, the material is so fine-grained that it is easily inhaled during use and then gets into the respiratory organs. Here, in turn, the fine, but still quite sharp stone dust can cause painful irritation. Therefore, always work with respiratory protection whenever possible.

What does stone meal cost?

The prices for rock flour vary and depend heavily on which product you want to purchase in which package size. Depending on whether it is a well-known brand or a discounter product, the material can be just as expensive as it is cheap. In addition, the composition is also relevant for the price: High-quality stone flours made from lava rock are generally more expensive than cheap variants made from sand and limestone. So it is not the price that decides here, but the desired application.

If possible, always use large packages from 25 kilograms. These are cheaper in terms of the kilo price, and if the product is to really deliver visible results in the garden, you will need quite large quantities of it. Stone meal can basically be kept indefinitely as soon as it is kept dry.

What alternatives are there to stone flour?

Depending on what you do with it and what you want to achieve, you have different alternatives to stone flour. If the pH value is acidic, you can also use garden lime (€ 9.46 on Amazon *) to improve the soil. With normal soil, compost or rotted manure are very suitable. These materials also have a fertilizing effect, which in turn cannot be used with stone dust. Algae lime also helps against pests, and self-made herbal manure, such as nettle or horsetail based, is suitable for combating and preventing plant diseases.


Instead of liming the fruit trees in winter to protect them from pests and frost cracks, you can also use clay powder mixed with water. This protects against cold damage just as well and seals up the loopholes that many pests like to use as winter quarters.