When we were designing Culm, we didn't start with a list of materials we liked the look of. We started with a question: what properties does a cat scratcher actually need from its materials? And what happens to those materials when the product is no longer wanted?
The answers shaped every decision. Here's what we found — and why we chose bamboo for the post and woven sisal for the sleeve.
What your cat actually does to a scratcher
It's worth starting here, because the material requirements for a cat scratcher are genuinely specific. When a cat scratches, they're doing several things at once: stretching the shoulder and forelimb muscles, shedding the outer sheath of their claws, and — critically — leaving a visual and scent mark. The last of these explains why cats often favour the same spot repeatedly, and why a worn surface is often more appealing to them than a fresh one.
From a materials perspective, this means the surface needs to: provide enough resistance to satisfy the stretching reflex, have a texture that allows the claw sheath to catch and pull away cleanly, and be able to absorb repeated compressive and shear forces without disintegrating immediately.
The post itself needs to: remain upright and stable under lateral force, not splinter or deform under load, and ideally not shed particles that a cat could ingest.
The case for bamboo
Bamboo isn't a wood — it's a grass. But its culm (the hollow cylindrical stalk, which is also where we got our name) has a hardness and density that rivals many timber species. Moso bamboo, the species most commonly used in furniture and construction, reaches full structural maturity in around five years and can be harvested without killing the plant, which regenerates from the existing root system.
We chose bamboo for the Culm post for a combination of structural and environmental reasons. Structurally, it's harder than most softwoods and won't flex or deform under the lateral forces generated by a scratching cat. It doesn't splinter in the way that low-grade timber can, and it won't shed fibres or particles that could be problematic if ingested in small quantities.
Environmentally, the story is compelling. Bamboo sequesters carbon during its rapid growth phase, requires no pesticides or fertilisers in normal conditions, and — unlike MDF — contains no resin binders or formaldehyde compounds that create problems at end of life. At the end of the post's lifespan (which we'd expect to be many years), it can in principle be chipped, composted, or used for biomass, depending on how it's been treated.
"Some bamboo species grow close to a metre per day. The timber equivalent would take decades. That's not a small difference in the context of material supply chains."
We should be honest about one nuance: bamboo is typically grown in East Asia, which means transport emissions are part of its environmental footprint. This is a genuine trade-off, and we don't pretend otherwise. We've mitigated it where possible by selecting suppliers who work with responsible sourcing standards, and by designing the post to last a very long time — meaning the transport footprint is amortised over years, not months.
Sisal rope versus woven sisal
Almost every conversation about scratcher surfaces treats sisal as one thing. It isn't. The same fibre reaches your cat in two completely different forms, and the difference between them decides whether the product can ever be repaired.
Sisal comes from the agave plant, grown primarily in East Africa and Brazil. It produces a strong, stiff fibre that resists saltwater degradation and is used widely in rope, twine and matting. Spun into rope and wound tightly around a post, it makes an excellent scratching surface — which is why it is on almost every scratcher sold. The catch is how it is fixed. Wound rope is bonded in place with adhesive, so it cannot be removed cleanly for replacement or disposal. It also frays strand by strand rather than wearing evenly, which is why a rope post looks finished long before the post underneath is.
The same agave fibre can be spun into yarn and woven into a dense cloth instead — around 1,000g per square metre, closer to a heavy matting than a textile. Woven, it wears evenly across its face rather than unravelling from a cut end, and critically it can be made into a structural sleeve that slides over a post with no adhesive at all. Cats get the fibre they already respond to. The post underneath stays untouched and reusable.
We prototyped the sleeve in jute first, on the theory that a slightly softer fibre would be kinder under the claw. Our own testing said otherwise — cats were consistently less interested in jute than in sisal. So the sleeve moved to woven sisal cloth, which keeps the surface cats actually choose and still slides off when it is worn. The form changed; the principle did not. Replaceability is the whole system.
What "natural" actually means on pet product labels
This is worth a brief detour, because the word is used promiscuously. In the UK, "natural" on a product label has no regulated definition for pet products. It can mean that the primary material started as a plant. It says nothing about how that material was processed, what it was bonded with, or what happens to it at end of life.
A scratching post can be labelled "natural sisal" while bonded to an MDF core with formaldehyde-containing adhesive, mounted on a polypropylene base, and packed in non-recyclable plastic film. Every individual claim might technically be true. The overall picture is less clear.
We try to be specific about what we mean. Culm uses natural bamboo culm (not MDF or engineered wood) and dense woven sisal cloth (not synthetic carpet, and not rope bonded on with adhesive). When we say a material is lower-impact, we'll tell you why — and we'll acknowledge where we're still figuring things out.
The honest summary
No material choice is perfect. Bamboo travels a long way. Sisal requires land and processing water to produce. Processing any natural material has a footprint. But the relevant comparison isn't bamboo versus some idealised zero-impact alternative — it's bamboo versus MDF, and a replaceable woven sisal sleeve versus synthetic carpet or rope bonded on for good.
On that comparison, we're confident our choices hold up. And the replaceable sleeve system means that even the highest-impact part of the product — the surface that gets used up — is produced and disposed of in the smallest possible quantity, as infrequently as possible.
That's the principle. And it started with taking the materials question seriously.