Stone flour is extremely versatile in the garden and is suitable both for soil improvement and for controlling fungal diseases, pests and weeds. In this article we will tell you how this works and what you should pay attention to.

Stone flour is used, among other things, to improve the soil, but it can do a lot more

Table of Contents

Show all
  1. the essentials in brief
  2. What is stone flour?
  3. possible applications
  4. buy rock flour
  5. frequently asked Questions

    6. the essentials in brief

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

    What is stone flour?

    Stone flour or rock flour (14.13€) is exactly what its name says: very finely ground rock. However, not just any stone is used, because depending on the desired 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

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

    digression

    Is there a difference between rock dust and primary rock dust?

    In fact, there is a serious difference between rock flour and primary rock flour. The latter consists of rocks of volcanic origin, which 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 the formation of humus and ensures better water storage capacity. Stone flour, on the other hand, can also consist of other types of stone with completely different properties, such as clay minerals.

    possible applications

    Stone flour is mainly used for soil improvement

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

    Stone flour as a soil improver

    “Prime rock flour 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 fall back on primary rock flour, as only rocks of volcanic origin have the necessary proportion of minerals and trace elements. Even if this rock flour 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 rock dust 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 powdered clay, as this improves the water storage capacity of these very permeable subsoils.
    • improvement of soil life: The minerals and trace elements contained in stone flour are immediately available to soil organisms, so that they contribute directly to the formation of humus. The higher humus content in turn benefits vegetables and other garden plants without them being threatened by over-fertilization.
    • Increase in soil fertility: Rock dust 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. Depending on the type of stone used, rock flour is also suitable for improving a pH value that is too low.
    • Slow plant availability: Since the rock dust must first be completely weathered 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 types of stone dust

    There are various primary rock flours that consist of different parent rocks. We have put together a clear overview of what rock dust you use for in the garden in this table.

    parent rock Main ingredients Possible areas of application
    basalt Iron, magnesium, other minerals and trace elements Supply of minerals and trace elements, increase of soil life in the garden soil and in the compost
    diabase Iron, magnesium, other minerals and trace elements, especially calcium Supply of minerals and trace elements, increase in soil life in the garden soil and in compost, lowering of the pH value of overly alkaline soils
    granite lower mineral content Increasing soil life in garden soil and compost, lowering the pH of overly alkaline soils
    bentonite clay minerals Improvement of the water storage capacity, improvement of the ratio of clay and humus, especially for sandy soils
    zeolite lower mineral content Improvement of water storage capacity, strongly alkaline effect

    tips

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

    dosage

    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 specific product selected determine how much of the material you should or may apply. Therefore, study the manufacturer's recommendations carefully and be sure to measure the pH value of your garden soil before use. Incidentally, in order for a noticeable effect to occur, the material must be applied regularly - usually annually - one or two applications usually show no noticeable success.

    application

    Stone dust can be sprinkled directly onto the ground

    Rock dust can either be spread and worked into the soil or dissolved in liquids (e.g. irrigation water or plant manure) and applied in this way. The material is also very well suited to stimulating microbial life in the compost and thus accelerating the decomposition of the organic material - quite apart from the fact that the nutrients contained in the rock flour are also added to the compost and thus enrich it with minerals.

    There are basically three ways to spread bedrock dust:

    • 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 plants

    To work the rock flour into the soil, proceed as follows:

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

    During the growing season, you simply add the rock flour to the irrigation water or to a self-made plant manure. The latter also offers the advantage that the brew smells less intense - the material binds the unpleasant smell.

    digression

    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 store. 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 powder to neutralize the respective degree of acidity.

    crop protection

    However, stone flour is not only suitable for soil improvement, but can also be used as a plant protection product to combat pests and fungal diseases. Rock types rich in silicic acid, such as granite, are predestined for this purpose and repel both animal and fungal attackers.

    tips

    But be careful! Some plants do not tolerate rock flour. These include above all plants with a preference for acidic soils such as hydrangeas, rhododendrons and azaleas, camellias and blueberry bushes.

    Against fungal diseases

    Mixed with water, rock flour is a great remedy for fungal diseases

    Silicic acid strengthens the plant tissue and makes it less susceptible to the invasion of fungal pathogens. In order for your plants to benefit from this property, prepare a spray mixture from granite or other siliceous stone flour:

    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 don't use the entire amount right away, you can save the rest until the next application. Then, however, the spray liquid should first be stirred thoroughly, since the rock flour will settle.

    Against pests

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

    Against snails

    Snails are probably the biggest nuisance in any garden. It is often difficult to stop the voracious little animals from eating the lettuce and other tasty vegetables and ornamental plants. With a protective ring made of stone flour, about five to ten centimeters wide, you keep snails away from your garden plants and at the same time ensure that the soil and plants receive an extra portion of minerals. On the other hand, an intensely smelling paste made of stone flour and crushed garlic and chopped onions, which you bring into the rodents' corridors, should help against voles.

    Against weeds in joints

    youtube

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

    However, do not use just any stone powder for this purpose, but rather low-nutrient granite powder. This type of stone contains only a few growth-promoting minerals and is also specially prepared by some manufacturers (e.g. Dansand) as a jointing agent. Stone flour for grouting is available in different colors to match the coloring of the terrace tiles or paving stones.

    Where can I get stone dust?

    Stone dust is generally available in every hardware and garden store, and discount stores also have good deals from time to time. However, before you access it, read the table of contents first. Not every stone powder is suitable for every purpose and the cheap discounter offers in particular often contain mainly sand-lime brick or granite - both of which are useless for soil improvement, for example. If you are looking for primary rock flour, be particularly careful: Since this designation is not legally protected, high-quality lava rock is not always used for it.

    frequently asked Questions

    Is stone dust poisonous?

    No, stone dust is not toxic. There are even varieties that are suitable for human consumption (and are supposed to be good for your health, but is that really true?). However, the material is so fine-grained that it is easily inhaled during use and then enters the respiratory organs. Here, on the other hand, the fine but still very sharp stone powder can cause painful irritation. Therefore, always work with respiratory protection if possible.

    How much does stone flour cost?

    Stone dust prices vary and depend heavily on which product you want to buy and 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 flour made from lava rock is generally more expensive than cheap variants made from sand and limestone. The decisive factor here is not the price, but the desired application.

    If possible, always use large packages from 25 kilograms. These are cheaper per kilo, and if you want the product to really deliver visible results in the garden, you need fairly large quantities of it. Stone flour basically has an indefinite shelf life 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 dust. You can also use garden lime (€9.70) to improve the soil if the pH is acidic. With normal soil, compost or rotted stable manure are very suitable. These materials also have a fertilizing effect, which stone flour cannot serve with. Algae lime also helps against pests, and home-made plant manure, for example based on stinging nettles or horsetail, is suitable for combating and preventing plant diseases.

    tips

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

Category:

Garden design