Cold hardiness & minimum temperature

Is Castilian Heron's Bill (Erodium castellanum)cold hardy? Hardiness zone & min temp

Also called Castilian Heron's Bill, Heron's Bill, Castilian Erodium.

More about castilian heron's bill

About Castilian Heron's Bill

Erodium castellanum · also called Castilian Heron's Bill, Heron's Bill · flowering

Erodium castellanum is a compact, dwarf alpine perennial native to the mountains and plateaus of central Spain, producing an abundance of large cerise-pink flowers — each up to 2.5 cm across with distinctive dark netted blotching on the upper petals — over a long season from late spring through summer. It forms tight, flat clumps of pinnate, parsley-like, deeply cut foliage and grows at roughly half the size of the more widely grown Erodium manescavii, making it ideal for troughs, rock gardens, and scree beds. Sharp drainage in a full-sun position is essential for survival, particularly over winter. Erodium species are absent from the ASPCA Toxic Plants database, so toxicity cannot be confirmed as pet-safe; it is classified as mildly-toxic as a precaution.

Cold limit: USDA 5-8 · RHS H5 (-15 to 30°C)

Watch for — Winter wet and crown rot: The primary killer of this species in UK and northern US gardens; excess soil moisture around the crown in cold winters causes rapid fungal collapse — plant in scree or a trough with excellent drainage, and protect with a pane of glass or cloche during very wet winters.

What castilian heron's bill's hardiness rating actually means

Yes — castilian heron's bill is genuinely cold hardy. Rated RHS H5 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 5-8 — 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 −15 to −10 °C. Castilian Heron's Bill is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for castilian heron's bill as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 castilian heron's bill go outside or overwinter — and where?

Plant it out within USDA 5-8 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 castilian heron's bill can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Castilian Heron's Bill hardiness — frequently asked questions

Is castilian heron's bill cold hardy?

Yes — castilian heron's bill is genuinely cold hardy. Rated RHS H5 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Castilian Heron's Bill is hardy across USDA 5-8; 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 castilian heron's bill can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Castilian Heron's Bill is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is castilian heron's bill?

Castilian Heron's Bill is rated USDA 5-8 and RHS H5 — Hardy in most of the UK and in cold winters.

Can castilian heron's bill survive winter outside?

Plant it out within USDA 5-8 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 castilian heron's bill below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.