Cold hardiness & minimum temperature

Is Silverbush (Convolvulus cneorum)cold hardy? Hardiness zone & min temp

Also called Silverbush, Bush morning glory, Shrubby bindweed.

More about silverbush

About Silverbush

Convolvulus cneorum · also called Silverbush, Bush morning glory · flowering

Convolvulus cneorum is a compact, evergreen Mediterranean shrub native to rocky limestone hillsides of the western Mediterranean basin, prized for its intensely silvery, silky foliage and a long succession of white funnel-shaped flowers flushed pink in bud. It must have full sun and sharp drainage — poor drainage, especially combined with winter wet, is the most common cause of death. Keep it in low-fertility soil to maintain compactness and vigour. It is not considered toxic to pets or humans.

Cold limit: USDA 8-10 · RHS H4 (-10°C to 35°C)

Watch for — Root rot / winter wet: The leading cause of plant loss; ensure beds drain freely and consider raising plants on mounds or in containers in high-rainfall gardens.

What silverbush's hardiness rating actually means

Yes — silverbush is genuinely cold hardy. Rated RHS H4 and USDA 8-10, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 8-10 — 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 −10 to −5 °C. Silverbush is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for silverbush as it gets too cold:

It tolerates winter lows to about −10 to −5 °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 silverbush go outside or overwinter — and where?

Plant it out within USDA 8-10 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 silverbush can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Silverbush hardiness — frequently asked questions

Is silverbush cold hardy?

Yes — silverbush is genuinely cold hardy. Rated RHS H4 and USDA 8-10, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Silverbush is hardy across USDA 8-10; 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 silverbush can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Silverbush is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is silverbush?

Silverbush is rated USDA 8-10 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can silverbush survive winter outside?

Plant it out within USDA 8-10 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 silverbush below its minimum temperature?

It tolerates winter lows to about −10 to −5 °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.