What this site does

Can I Plant It cross-references the four main plant hardiness systems — the American USDA zones, the British RHS ratings, the Canadian zones, and the Australian ANBG zones — so you can take a rating from any book, nursery label or overseas catalogue and work out what it means where you actually garden. Answer a short quiz about your local climate and you get your equivalent rating in all four systems at once; paste in a rating you have already found and you get a straight answer on whether it suits your conditions.

Why there are four systems — and why the conversions are approximate

The systems do not line up because they were never measuring the same thing. The USDA system records one number: the average annual coldest winter temperature at a location, in thirteen bands. A plant rated USDA zone 7 survives zone 7 and anything milder — the number describes the place, and reads downward ("tolerates down to"). The Canadian system looks similar but is built from seven climate variables — including winter cold, frost-free days, summer heat, rainfall, snow cover and wind — so its zones capture more than temperature alone.

The RHS system works the other way around. Its ratings, H1a through H7, describe the plant rather than the place, and read upward: an H5 plant needs at least a certain level of cold tolerance to come through an average British winter. Reading an RHS rating as though it were a USDA zone — or the reverse — is the classic mistake, and a reliable way to lose a plant. The Australian ANBG system uses winter minimums like the USDA one, but only reaches about −15 °C, and across most of Australia winter cold is rarely the limiting factor: heat, drought and humidity matter more. Because each scale rests on a different measurement, a conversion between them is a close approximation rather than an exact swap — so give yourself a band of margin either way.

Quiz or cross-check?

Use the quiz when you want to know your own zones. It asks eight questions about your conditions and returns your equivalent rating in every system, which you can save in your browser and reuse. Use the cross-check when you already have a rating — from a plant label, a catalogue or a gardening book — and simply want to know whether that plant will cope where you are. The quiz describes your garden; the cross-check tests a single plant against it.

Browse the guides

Each system has its own plain-language guide, and the full catalogue is browsable by category:

• USDA hardiness zones — the thirteen-band United States system, based on average winter minimum temperature.
• RHS hardiness ratings — the UK system that rates a plant's cold tolerance rather than a place.
• Canadian plant hardiness zones — a seven-variable system that weighs more than winter cold.
• Australian (ANBG) zones — winter-minimum zones calibrated for Australian gardens.
• Plant database — 1,049 plants grouped by category, each rated in all four systems.