Brunnings Propagating Sand, and why sand won't fix clay

What propagating sand is for, and one thing it definitely is not for

A cutting has no roots, so for the first few weeks it can't take up much water and it can't feed itself either. What it needs is a medium that holds enough moisture to keep the stem alive while draining hard enough that the cut end never sits wet, and it wants almost no nutrient in it at all. Coarse sand does exactly that. It has been the propagator's standby for about as long as people have been striking cuttings.

Why coarse, and why washed

Brunnings Propagating Sand is a coarse, washed grade rather than the fine stuff out of a sandpit or a bag of bricklayer's sand. Grain size is the whole point. Coarse grains leave big air spaces between them that water runs out of and air runs back into, while fine sand packs down tight and holds water in a way that rots a cut stem in about a week.

Being low in nutrient is a feature too. There's nothing in it for the fungi that cause damping off to live on, and a cutting has no roots to take up fertiliser anyway, so anything rich in the tray is doing nothing except feeding the problem.

How to strike a cutting in it

• Fill a pot or tray and moisten it before the cutting goes anywhere near it, then let the excess drain right off.
• Take the cutting off healthy current-season growth and cut cleanly just below a node. Strip the lower leaves so that nothing is buried in the sand.
• Dip the cut end in a rooting hormone if you're doing something that's slow to strike, and knock the excess off.
• Make the hole with a pencil first rather than pushing the stem in, because forcing it scrapes the hormone straight back off.
• Firm the sand gently around it so there's contact, then keep the whole lot somewhere bright but out of direct sun.

Humidity is the part most people miss. A cutting with no roots is losing water through its leaves the whole time, so a clear bag or a cut-down bottle over the top makes an enormous difference, as long as you keep it off the leaves and air it now and then. Check for roots by tugging very gently after a few weeks, and if it resists, something is happening down there.

The other jobs it does

The same coarse sand is worth having around for mixing into a potting mix that's holding more water than a plant wants, particularly for cactus and succulents in pots, and for topping a seed tray where you want the surface to dry quickly between waterings.

Sand does not fix clay, and this one matters

This gets repeated constantly and it's wrong in a way that costs people a lot of effort. Adding a modest amount of sand to a heavy clay soil doesn't open it up, it does the opposite: the sand grains fill the spaces between the clay particles and you end up with something closer to a poor concrete than to a garden bed. To actually change a clay soil by adding sand you'd need to add an enormous proportion of it, far more than anyone is going to barrow in, and you'd still have made nothing useful.

What genuinely improves clay is organic matter, going in year after year, because it feeds the biology that builds crumb structure and it keeps working after you've stopped digging. Where the clay is the dispersive kind that goes to soup in water, gypsum helps as well, and it does that by chemistry rather than by texture, so a few kilos does something a barrow of sand never will. Lime is a pH product rather than a clay product, and it's a separate question again.

Shop related products

• Brunnings Propagating Sand 5L. Coarse washed sand for striking cuttings and sharpening a mix.
• Multicrop Take Root Cutting Powder. For the woody things that are slow to strike on their own.
• Brunnings Perlite 5L. The lighter option for the same job, and it doesn't compact at all.
• Brunnings Garden Compost with Seaweed 25L. The thing that actually improves a clay bed.

Did you know we also carry gypsum in 10kg and 20kg bags in the shop, along with Take Root as a liquid rather than a powder. Neither is listed on the website, so give us a ring on (08) 8536 4333 to check what's on the shelf, or come and look through the garden centre.

Read next

• How to grow vegetables in clay soil
• Brunnings Perlite, what it does and when to use it
• Compacted soil, what it does and how to fix it

I take far more cuttings than I've got room for, so half the shed is trays and the other half is me pretending that counts as a plan.

Cheers,
Candeece

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