Cold hardiness & minimum temperature

Is Czar Plum (Prunus domestica 'Czar')cold hardy? Hardiness zone & min temp

Also called Czar plum, culinary plum.

More about czar plum

About Czar Plum

Prunus domestica 'Czar' · also called Czar plum, culinary plum · edible

Czar is a hardy, reliable English culinary plum from the 1870s, bearing heavy crops of small-to-medium blue-black fruit with greenish-yellow flesh, ideal for cooking, jam and stewing. Self-fertile and frost-tolerant in blossom, it crops dependably even in cooler, less sheltered gardens, ripening in late July to August.

Cold limit: USDA 5-8 (frost-resistant blossom, hardy) · RHS H6 (-25 to 30°C)

Watch for — Silver leaf: A fungal disease entering through wounds, causing silvery leaves and dieback. Prune only in summer when spores are scarce and the tree heals fast, never in winter, and remove infected wood.

What czar plum's hardiness rating actually means

Yes — czar plum is genuinely cold hardy. Rated RHS H6 and USDA 5-8 (frost-resistant blossom, hardy), 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 5-8 (frost-resistant blossom, hardy) — 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. Czar Plum is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for czar plum 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 czar plum go outside or overwinter — and where?

Plant it out within USDA 5-8 (frost-resistant blossom, hardy) 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 czar plum can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Czar Plum hardiness — frequently asked questions

Is czar plum cold hardy?

Yes — czar plum is genuinely cold hardy. Rated RHS H6 and USDA 5-8 (frost-resistant blossom, hardy), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Czar Plum is hardy across USDA 5-8 (frost-resistant blossom, hardy); 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 czar plum can survive?

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

What hardiness zone is czar plum?

Czar Plum is rated USDA 5-8 (frost-resistant blossom, hardy) and RHS H6 — Hardy throughout the UK and northern Europe.

Can czar plum survive winter outside?

Plant it out within USDA 5-8 (frost-resistant blossom, hardy) 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 czar plum 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.