Cold hardiness & minimum temperature

Is Faulkner box (Buxus microphylla 'Faulkner')cold hardy? Hardiness zone & min temp

Also called Faulkner box, Faulkner boxwood, small-leaved box Faulkner.

More about faulkner box

About Faulkner box

Buxus microphylla 'Faulkner' · also called Faulkner box, Faulkner boxwood · flowering

Faulkner box is a compact, slow-growing cultivar of Japanese boxwood with dense, glossy, dark bluish-green foliage that holds its colour well in winter. It is notably more resistant to box blight than many common boxwoods, making it a reliable choice for formal topiary, balls, and low hedging.

Cold limit: USDA 5-9 · RHS H6 (-20°C to 35°C)

Watch for — Root rot in containers: Container-grown specimens are vulnerable to Phytophthora root rot if overwatered or if pots lack adequate drainage holes. Use free-draining compost mixed with 20–30% perlite, and elevate pots to allow free drainage. Reduce watering frequency in winter.

What faulkner box's hardiness rating actually means

Yes — faulkner box is genuinely cold hardy. Rated RHS H6 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H6 means: Hardy throughout the UK and northern Europe. On the US scale that maps to USDA 5-9 — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

Minimum survivable temperature is roughly about −20 to −15 °C. Faulkner box is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for faulkner box as it gets too cold:

It tolerates winter lows to about −20 to −15 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can faulkner box go outside or overwinter — and where?

Plant it out within USDA 5-9 and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when faulkner box can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Faulkner box hardiness — frequently asked questions

Is faulkner box cold hardy?

Yes — faulkner box is genuinely cold hardy. Rated RHS H6 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Faulkner box is hardy across USDA 5-9; it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature faulkner box can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Faulkner box is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is faulkner box?

Faulkner box is rated USDA 5-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can faulkner box survive winter outside?

Plant it out within USDA 5-9 and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to faulkner box below its minimum temperature?

It tolerates winter lows to about −20 to −15 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.