Cold hardiness & minimum temperature

Is Digyna Sweet Box (Sarcococca hookeriana var. digyna)cold hardy? Hardiness zone & min temp

Also called Small Himalayan Sweet Box, Digyna Sarcococca, Winter Sweet Box.

More about digyna sweet box

About Digyna Sweet Box

Sarcococca hookeriana var. digyna · also called Small Himalayan Sweet Box, Digyna Sarcococca · flowering

Digyna Sweet Box is a compact, clump-forming evergreen shrub valued for its intensely fragrant small white flowers in midwinter and glossy black berries that follow. It tolerates deep shade and dry conditions better than most shrubs, making it ideal for difficult spots beneath trees. Not listed as toxic by the ASPCA; generally considered low-risk for pets.

Cold limit: USDA 6-9 · RHS H6 (-20–25°C)

Watch for — Scale insects: Waxy brown bumps on stems and undersides of leaves; treat with horticultural oil in late winter.

What digyna sweet box's hardiness rating actually means

Yes — digyna sweet box is genuinely cold hardy. Rated RHS H6 and USDA 6-9, 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 6-9 — 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. Digyna Sweet Box is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for digyna sweet 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 digyna sweet box go outside or overwinter — and where?

Plant it out within USDA 6-9 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 digyna sweet box can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Digyna Sweet Box hardiness — frequently asked questions

Is digyna sweet box cold hardy?

Yes — digyna sweet box is genuinely cold hardy. Rated RHS H6 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Digyna Sweet Box is hardy across USDA 6-9; 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 digyna sweet box can survive?

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

What hardiness zone is digyna sweet box?

Digyna Sweet Box is rated USDA 6-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can digyna sweet box survive winter outside?

Plant it out within USDA 6-9 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 digyna sweet 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.