Cold hardiness & minimum temperature

Is Itoh Peony 'Bartzella' (Paeonia 'Bartzella')cold hardy? Hardiness zone & min temp

Also called Itoh peony, Intersectional peony.

More about itoh peony 'bartzella'

About Itoh Peony 'Bartzella'

Paeonia 'Bartzella' · also called Itoh peony, Intersectional peony · flowering

'Bartzella' is the standout yellow Itoh (intersectional) peony, a cross between herbaceous and tree peonies. It carries large, semi-double, lemon-yellow flowers with red flares on strong, self-supporting stems that never flop. The handsome divided foliage stays attractive all summer, and the plant dies back to ground level each winter like a herbaceous peony.

Cold limit: USDA 4-9 · RHS H6 (-30 to 30°C)

What itoh peony 'bartzella''s hardiness rating actually means

Yes — itoh peony 'bartzella' is genuinely cold hardy. Rated RHS H6 and USDA 4-9, 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 4-9 — 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. Itoh Peony 'Bartzella' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for itoh peony 'bartzella' 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 itoh peony 'bartzella' go outside or overwinter — and where?

Plant it out within USDA 4-9 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 itoh peony 'bartzella' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Itoh Peony 'Bartzella' hardiness — frequently asked questions

Is itoh peony 'bartzella' cold hardy?

Yes — itoh peony 'bartzella' is genuinely cold hardy. Rated RHS H6 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Itoh Peony 'Bartzella' is hardy across USDA 4-9; 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 itoh peony 'bartzella' can survive?

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

What hardiness zone is itoh peony 'bartzella'?

Itoh Peony 'Bartzella' is rated USDA 4-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can itoh peony 'bartzella' survive winter outside?

Plant it out within USDA 4-9 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 itoh peony 'bartzella' 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.