Why Pots Crack — and How to Prevent It

We get the call almost every winter: "my pot just cracked, what's wrong with it?" Almost always, the cause turns out to be one of three things — and two of them are preventable.

Cause 1 — Frost (the big one)

Water inside the pot wall freezes overnight, expands by 9%, and cracks the material. The fix:

• Buy frost-resistant material. Clay is the worst offender (very porous), solid concrete is moderate, GRC fiber cement is the most resistant of the popular outdoor materials.
• If you already have clay pots: wrap them in hessian for winter, or move them under cover. We've covered this in detail in the Highveld frost article.

Cause 2 — Roots (the slow killer)

A plant left in the same pot for too long fills the pot with roots until there's almost no soil left. The roots then start pushing outward against the wall — slowly, over months — until something has to give.

The fix:

• Re-pot every 1-3 years. Slide the plant out in spring, untangle the roots, move to a slightly bigger pot. Quick guide: How to choose pot size.
• For trees and large shrubs in pots that can't be sized up: root-prune every 2 years (slice off the outer 3 cm of the root ball with a sharp spade) and replace the soil.

Cause 3 — Drops and knocks

You'd be surprised how often a pot cracks because someone tried to reposition it loaded with wet soil. A medium pot full of damp soil can weigh 30+ kg — drop the bottom edge onto a paving slab and even GRC will chip.

The fix:

• Always empty pots before moving them. If you can't, use a pot trolley or two people, lift cleanly, set down gently.
• Position pots on something soft. Cork pads, rubber feet, or a thin layer of mulch under the rim cushions everything against frost upheaval AND against the inevitable knocks.

What about cracks that already happened?

Small cracks (under 5 mm) in a GRC pot can usually be sealed with clear silicone from the inside. The pot becomes a permanent fixture — you can't move it without re-cracking — but the plant survives.

Larger cracks: the pot's done. If it's one of ours, send us a photo — we offer replacement discounts on warrantied splits within 12 months of purchase, and there's almost always something we can do.

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