Horticultural grit is a specialized, inert soil amendment designed to improve the physical structure of growing media. It consists of hard, crushed rock particles that are washed to ensure a neutral pH, preventing unintended alteration of soil acidity or alkalinity. Its primary function is to create permanent air pockets within potting mixes or heavy garden soil, significantly enhancing drainage and aeration. By interrupting the fine structure of soil particles, grit prevents compaction and allows excess water to escape efficiently. This stability and drainage make it a valuable component for various gardening applications, especially for plants requiring well-draining conditions.
Understanding the Different Types of Grit
Horticultural grit is an umbrella term for several coarse, granular aggregates, each offering different characteristics. The most common form is crushed granite, which is dense, heavy, and durable, providing reliable, long-term drainage without breaking down. If limestone is used, it must be thoroughly washed to remove alkaline residue and ensure it remains pH-neutral for sensitive plants.
Lighter alternatives include volcanic sources like pumice and lava rock, which are highly porous despite their reduced weight. These materials are inert and pH-neutral, but their internal structure allows them to absorb a small amount of water and nutrients, benefiting certain potting mixes. Calcined clay, often sold as expanded clay aggregate (LECA), is another engineered material fired to create lightweight, structured particles for drainage. Particle size is also a key distinction: smaller grades (1–4 mm) are preferred for fine potting media or bonsai, while 2–6 mm grades suit general soil improvement and container drainage.
Major Retailers and Local Garden Centers
For immediate and smaller-scale needs, physical retailers offer the quickest way to source horticultural grit. Large home improvement chains often stock bagged aggregates in their landscaping or garden supply sections, typically in 20 to 25-kilogram bags. If true horticultural grit is unavailable, look for alternatives like coarse paver base or washed granite poultry grit, ensuring they are free of added chemicals or salts. These alternatives function as crushed, inert stone, but confirming a neutral pH is recommended.
The product is commonly located near potting soil, compost, or sand and gravel supplies within these large stores. Independent, local garden centers frequently offer a higher quality, dedicated horticultural grit, often sold under specific brand names or sourced from local quarries. These smaller operations may also sell grit by the scoop or in unbranded, larger bags, providing a cost-effective option for medium-sized projects. Garden center staff are usually knowledgeable about the specific grade and composition of the grit they stock, which is useful when selecting material for specialized plants like cacti or alpines.
Online and Bulk Purchasing Options
For gardeners needing significant quantities or specialized types of grit, online suppliers and bulk aggregate companies are the primary sources. Online marketplaces provide convenience for ordering smaller, specialized bags of materials like pumice or calcined clay that may not be available locally. However, these options often carry a premium price due to shipping costs, which can be substantial for heavy stone products.
When large volumes are necessary, such as for improving garden beds or mixing custom soil, landscape supply companies and aggregate dealers offer the best value. These businesses typically sell grit in bulk bags (approximately 850 kg to one tonne) or in loose loads delivered directly to the site. Purchasing in bulk requires adequate storage space and consideration for delivery logistics, as palletized bags require specific drop-off access or a forklift. Sourcing from these suppliers ensures access to large volumes of consistent, graded material for major projects.