What is mulch glue — and does it actually work?

"Mulch glue" has become the catch-all name for a family of products that stop loose landscaping materials — mulch, pebbles, gravel, decomposed granite — from blowing, washing or scattering away. If you've seen the TikTok videos and wondered whether it's a real thing or a gimmick, here's the straight answer for New Zealand conditions.

1. What it actually is

A mulch binder is a liquid adhesive that you dilute with water and spray over the surface. As it dries it forms a clear, flexible film that bonds the top layer of material together — think of it as a light net over your mulch or pebbles rather than concrete. Done properly, the bed still looks completely natural.

2. The two main types in New Zealand

• Spray-on concentrates (like Landscape Lock) — diluted 1:3 to 1:6 with water and applied with a normal garden pressure sprayer. Suited to mulch, decorative pebbles and DIY paths. Low cost per square metre, easy to re-apply.
• Pour-on resins — thicker polyurethane products poured neat over gravel, setting into a harder surface. Suited to high-end permanent gravel surfaces; considerably more expensive per square metre and less DIY-friendly.

3. What to check before buying any binder

• Water permeability — rain and irrigation must still reach the soil. If a product seals the surface, your plants pay for it.
• Dries clear — you want your garden looking like your garden.
• Coverage per litre — compare diluted coverage, not bottle size. A concentrate that covers 15 m² per litre beats a cheaper bottle that covers 5.
• Cure time and weather — everything in this category needs a dry window (24–72 hours) to set. No exceptions.
• Clean-up — water clean-up before curing is the difference between a 5-minute rinse and a permanent stain on your driveway. Wet hard surfaces first, rinse overspray immediately.
• Safety — check the label for plant and pet safety claims and the safety data sheet.

4. Honest expectations

• It's not permanent. A spray-on binder typically holds up to 12 months depending on weather exposure and traffic, and you re-apply when you top up mulch.
• Water temporarily softens the bond — avoid scuffing treated areas right after rain. It firms again as it dries.
• It handles wind, rain and leaf blowers — not digging dogs or brush turkeys.
• Coverage varies with how porous your material is. Buy on the conservative end; sealed concentrate keeps.

5. Where to get it

Landscape Lock is available across New Zealand at Bunnings, Mitre 10 and selected garden and landscape suppliers. Full dilution rates and step-by-step instructions for every surface are in the application guide.

These are summary instructions and general guidance only — coverage rates are indicative and vary with substrate, porosity and technique. Always follow the full instructions before applying: download the Application Guide (PDF).