Updated/Fact-Chacked on June 14, 2023 by Gareth James
Everyone with a garden or allotment is interested in improving soil structure, trying to create the best growing medium possible. And one of the main methods is using horticultural grit.
Soil structure refers to the arrangement or organization of solid particles of soil and the spaces (pores) between them. It significantly impacts the soil’s ability to hold and circulate air, water, and nutrients vital for plant growth. The particles – sand, silt, and clay – bind together to form ‘aggregates’ or ‘peds’, which vary in size, shape, and strength.
These aggregates give the soil its texture and structure, ranging from sandy or loose to clayey or dense. Good soil structure has a crumbly texture, a balance between larger and smaller pores, and is vital for supporting healthy plant roots, facilitating drainage, and encouraging beneficial soil organisms.
What is horticultural grit?
Horticultural grit is a specific type used in gardening and horticulture for its beneficial impact on soil structure and plant health.
It is typically made from crushed rocks, like granite or quartzite, and comes in different grades, from fine to coarse. The particles are hard, sharp, and irregular, providing excellent drainage and preventing soil compaction, especially in clay soils.
This type of grit can also help stabilize larger plants and trees and be used as a decorative element on the soil surface or in pots. Despite its inert nature, meaning it doesn’t add nutrients to the soil, its physical benefits make it an essential tool in many gardening scenarios.
Components of horticultural grit
Horticultural grit is made from crushed granite stones or limestone. These stones naturally break down into smaller pieces with angled edges, which is why they are preferred. They promise excellent surface area, making excellent drainage suitable for a wide range of garden applications, especially improving soil structure.
Why use horticultural grit?
Horticultural grit is unlike any average soil improver used in landscaping and other garden activities. It is cleaned to remove all lime elements, a key factor that defines the soil. Neutral pH is very important for planting a wide range of plants, and horticultural grit mixed with any soil type does not affect its acidity or alkalinity.
Here is a summary of its benefits:
Some seeds and plants want acidic soil, while others prefer alkaline ones. You can mix horticultural grit with chosen ingredients to address the soil pH level issues. For instance, lime-based gravel can raise the pH, whereas grit treated with acidic ingredients can lower acidity.
Improving Soil Composition
Horticultural grit is known for drying out quickly and improving soil aeration, making it quite effective in composition. Mixing it in your garden will ensure proper drainage and aeration, which is important in the maximum consumption of compost organic matter.
You can mix horticultural grit with landscaping soil or clay to improve drainage. Rain and other water move through the mixture freely, ensuring better delivery of nutrients around the root system.
Better Air Flow
One of the biggest threats to your garden is heavy rains, which might leave soil waterlogged and compact. This happens especially with clay-rich soils, leaving very little room for the growth of roots. Gardeners can puncture the soil using an aerator or using horticultural grit. This ensures oxygen-rich soil, which is crucial for the growth of your plants.
How do you use horticultural grit?
Horticultural grit has found so many uses. Here are some of them:
Add it to your compost
As stated above, soil sticking together is something you want to avoid for better aeration. Add the grit to your compost, and you will never have to deal with such issues. Another approach is to mix one basket of loam with one basket of horticultural grit, and then one basket of leaf mould. This creates a perfect mix for a rock garden.
Aquatic ponds and seeds trays
If you are making an aquatic pond, apply a thin layer of grit at the top of the soil. This prevents the fish from stirring up mud. For those doing seeds trays, you can use a thin sprinkle of grit to prevent the seeds from dying when germinating.
Plants popular in rocky areas (alpines) can do well with some horticultural grit. You can use it to replicate their natural conditions using pots, giving the plants good space to grow. You will require equal measures of compost and horticultural grit to approx. 12 cm to the container’s rim.
Another great way to use this gravel is when building a scree garden. Scree is a common feature in the mountainous area, and it attempts to emulate natural features in the garden. Naturally, they are made by the freezing and thawing of rock parts that break into materials of different sizes.
Horticultural Grit V Perlite V Vermiculite
Horticultural grit, perlite, and vermiculite are all critical components in gardening, each bringing unique properties and benefits to the soil. Horticultural grit is a non-absorbent mineral that improves soil structure by promoting drainage and reducing compaction; ideal for succulents, cacti, and other plants that prefer a well-draining environment.
On the other hand, perlite, a type of volcanic glass heated to a high temperature until it pops like popcorn, provides excellent aeration and drainage while also being lightweight. It’s an excellent amendment for seed-starting mixes or plants needing well-aerated soil.
Vermiculite, also a mineral, expands when heated and has a higher water-holding capacity. It’s particularly useful in retaining moisture and nutrients in the soil, making it a suitable choice for plants that prefer consistently moist soil or for germinating seeds.
Each has its strengths and should be chosen based on your plant’s specific needs and the existing condition of your soil. Understanding their differences is key to tailoring the optimal growing environment for your plants.
Where can you purchase horticultural grit?
Horticultural grit is often sold in bulk bags of varying sizes and categories based on the colour. You can easily find them with your local suppliers of garden materials. The other option is to buy online so you don’t have to lug a 20kg bag around; see the link below for Vlax horticultural grit, which I have been buying for £17.99/20kg (free delivery with Prime).
Horticultural Grit FAQS
Is horticultural grit the same as gravel?
No, horticultural grit is not the same as gravel. While they are both made from crushed rock, the key difference lies in their size and texture. Horticultural grit has smaller, more uniform particles better suited for improving soil structure and drainage.
Can I use gravel instead of horticultural grit?
While gravel can be used to improve drainage, it’s not as effective as horticultural grit due to its larger particle size. For container plants or delicate plants that need good drainage and aeration, horticultural grit would be a better choice.
What is the difference between horticultural sand and grit?
The main difference between horticultural sand and grit is their particle size and composition. Sand has smaller particles than grit and is often used to lighten heavy soils and improve drainage. With its larger particles, grit is often used to aid in heavy clay soils or plants that need excellent drainage.
Why do British gardeners use grit?
British gardeners use grit mainly because many areas in the UK have heavy clay soils, which can hold too much water and become compacted. Adding grit improves the soil structure by increasing drainage and reducing compaction, creating a more suitable environment for plant roots.
Should I add grit to soil?
Adding grit to soil can benefit certain plants and specific soil types. For instance, plants that require well-drained soil, such as cacti, succulents, and alpines, will benefit from added grit. Also, if your garden soil is heavy and clay-like, adding grit can improve its structure by increasing aeration and drainage. However, if your soil is already well-draining or sandy, adding grit might not be necessary. Always consider the needs of the specific plants and the characteristics of your soil when deciding to add grit.
John Green is a 46-year-old graphic designer living in Durham. John is RHS level 3 certified and owns an allotment in Durham.