Granite derived product, ideal for adding to composts and soils to improve drainage and heavy soils.
Horticultural Grit brings essential drainage and aeration to garden soils with its 2-4mm granite derived particles. This practical grit effectively improves composts and breaks up heavy clays for healthier plants. Perfect for:
- mixing into composts and topsoil
- breaking up heavy clay soils
- preparing ground for planting
The durable particles of Horticultural Grit help promote strong root development and excellent water passage. A natural, low-maintenance alternative, ideal for renovating your outdoor space.
Horticultural Grit
Price range: £108.00 through £207.00 inc. VAT
Gravel Calculator
| Weight | N/A |
|---|---|
| Size | 2-4mm |
| Quantity | 10 x 20kg Mini Bags, 20 x 20kg Mini Bags, 40 x 20kg Mini Bags, 850kg Bulk Bag |
| Material | Granite, Grit |
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Specifications, Inspirational Ideas & DIY Guides
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Why Professionals & Homeowners Choose, Applications, DIY Guides & Inspirational Ideas, Maintenance, Purchasing Tips, FAQs, Related Products
Overview
I get asked about horticultural grit more than almost any other bag we sell, and the question usually hides the same misunderstanding: that one bag will fix a wet border. Ours is granite, graded to 2-4mm, at the finer end of the range (most UK grit is sold as 2-6mm). Granite is naturally lime-free, so it opens soil up without quietly pushing the pH towards alkaline the way limestone grit does, and that is the whole reason it can go near alpines and acid-lovers. Dry it reads grey with the usual granite flecking, and it darkens noticeably once it is wet. Used at the right rate it does three jobs nothing else does as well.
Why Professionals & Homeowners Choose Horticultural Grit
The case for grit over sand, perlite or another bag of compost comes down to five things.
- Granite grit is lime-free and pH neutral, which is the difference between a grit you can use around rhododendrons, heathers and alpines and one you cannot.
- The particles are angular rather than rounded, so they wedge against each other and hold air spaces open instead of rolling into a solid layer.
- At 2-4mm it mixes evenly through a potting compost and is still coarse enough to read as a proper collar around a plant neck.
- Grit does not rot down, so a border gritted properly stays open for years, where compost does its work and disappears within a couple of seasons.
- Stone is heavy, and 20kg is only about 12.5 litres of material, which is the honest limit of it: one bag goes nowhere in a border, and under-ordering is the commonest mistake with this product.
Horticultural Grit Applications
Everything I use grit for comes down to one job, keeping water away from roots and crowns that resent sitting wet. That means houseleeks (Sempervivum tectorum), sea thrift (Armeria maritima), the silver sulkers like Salvia argentea and Verbascum bombyciferum, and the Mediterranean shrubs: lavender, rosemary and cotton lavender (Santolina chamaecyparissus). It is the wrong material for anything wanting a moist root run, so hostas, astilbes and ferns get nothing from it, and a hungry vegetable bed wants organic matter rather than stone. It is a soil and potting material too, not a surface you walk on, since 2-4mm treads in and vanishes underfoot within a season.
One thing I would not do is tip a layer into the bottom of a pot and call it drainage. Mixed through the compost it works. Sitting in a band underneath, it is argued over at best.
- Potting mixes at 1 part grit to 1 part John Innes No.3 for alpines, going to around three parts grit to one of compost for cacti and dry-habitat succulents.
- Top-dressing alpines and rockery plants, where a 1cm collar goes round each neck and the grey, felted-leaved plants get more of it than the rest.
- Opening up a heavy clay border, where 4-6cm of grit goes in with compost and gets turned through the top 15-20cm.
- Finishing houseplant and container compost with a thin 1cm layer, which tidies the surface, keeps the plant's base out of wet compost and takes the edge off moss and algae.
- Seed and cutting mixes, where gritty compost keeps a pan open through a wet winter and a surface layer anchors the seed and holds down liverwort.
- Bulb planting, where a handful under each bulb keeps its base out of standing water.
DIY Guides & Inspirational Ideas
How I identify garden soils that need improving or removing.
Ben Parrot
Most rockeries fail due to a lack of drainage, poor stone placement, or choosing the wrong plants.
Ben Parrot
Horticultural Grit Maintenance
A grit collar is not a one-off job. On pots and alpine plantings, bring it back to about 1cm once a year in late autumn, because watering and rain wash it out from around the neck and winter is exactly when that gap does the damage. Grit worked down into a border is permanent, though I still top the surface up each autumn around the felted and silver-leaved plants, which suffer first. Otherwise, keep debris off it. Weeds seed into the soil and leaf litter that collects between the particles, not into the grit itself.
Purchasing Tips
Grit weighs around 1,600kg per cubic metre, so an 850kg bulk bag is a little over half a cubic metre and a 20kg mini bag holds about 12.5 litres. As a 1cm top dressing a bulk bag covers roughly 50m², or about 25m² at 2cm. Worked into clay at 5cm through the top 15-20cm, the same bag does about 10m², and that is the figure that surprises people. Our gravel calculator does the arithmetic for you. Order it all in one delivery where you can, because stone is a natural product and colour varies between batches, which shows most on a top dressing. Check the route from the kerb too, since a bulk bag arrives on a pallet and the driver moves it with a trolley jack that wants firm level ground. If the job is round the back or up steps, take the mini bags. And because you cannot judge grit from a photograph, read the stated size rather than the name on the bag: alpine, potting and horticultural grit are the same class of material, and the millimetres tell you what is actually arriving.
If you would rather talk your horticultural grit order through with a person, ring Outdoor Aggregates on 0330 043 7585. The office is open 7am to 7pm, seven days a week.
FAQs
What is horticultural grit made of?
Horticultural grit is crushed stone, and ours is granite graded to 2-4mm. Granite and quartzite are the usual UK parent rocks, because they break into angular pieces that hold their shape in a mix and are naturally free of lime.
Is horticultural grit the same as alpine grit or potting grit?
Alpine grit, potting grit and horticultural grit are the same class of material sold under different names, so the wording on the bag settles nothing. The stated particle size and whether it is lime-free are what actually differ.
Is horticultural grit lime free?
Granite horticultural grit is lime-free and pH neutral, so it will not push soil or compost towards alkaline. Limestone-based grit does raise pH over time, which matters for rhododendrons, camellias, heathers and most alpines.
How much horticultural grit do I need for clay soil?
Clay borders take 4-6cm of grit turned through the top 15-20cm, with compost going in at the same time, which comes to roughly one 850kg bulk bag per 10m². Grit at that rate without the organic matter sets rather than opens.
Can you use horticultural grit for succulents and cacti?
Horticultural grit suits cacti and succulents mixed about half and half with John Innes No.3, going to around three parts grit for species from genuinely dry habitats. A 1cm surface layer keeps the base of the plant out of wet compost.
Does horticultural grit stop slugs?
Horticultural grit deters slugs and snails rather than stopping them, and a determined one crosses it. I use it for the drainage and the dry collar it gives a plant, and keep slug control separate, with a tile or a grapefruit half left out as a trap.
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