Cold hardiness & minimum temperature

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

Also called Glandular Heron's Bill, Black-Eyed Heron's Bill, Glandular Stork's Bill.

More about glandular heron's bill

About Glandular Heron's Bill

Erodium glandulosum · also called Glandular Heron's Bill, Black-Eyed Heron's Bill · flowering

Erodium glandulosum is a compact herbaceous perennial native to the mountains of Spain and Portugal (Pyrenees and Iberian highlands), where it grows in rocky, well-drained limestone soils. It forms low, mound-like rosettes of glandular, silver-green, pinnately divided leaves and bears clusters of lilac-pink flowers with darker blotched upper petals throughout summer. The single most important care fact is that it demands sharp drainage and protection from prolonged winter wet, which will rot the crown far more readily than cold alone. Not documented as toxic to cats or dogs; classified as mildly-toxic due to limited species-specific ASPCA data.

Cold limit: USDA 5-9 · RHS H5 (-15 to 25°C)

Watch for — Crown rot: The most common killer; caused by waterlogged soil or poor air circulation in winter wet. Prevent by planting in raised beds or adding a collar of grit around the crown.

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

Yes — glandular heron's bill is genuinely cold hardy. Rated RHS H5 and USDA 5-9, 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 5-9 — 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 −15 to −10 °C. Glandular Heron's Bill is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for glandular 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 glandular heron's bill go outside or overwinter — and where?

Plant it out within USDA 5-9 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 glandular 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.

Glandular Heron's Bill hardiness — frequently asked questions

Is glandular heron's bill cold hardy?

Yes — glandular heron's bill is genuinely cold hardy. Rated RHS H5 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Glandular Heron's Bill is hardy across USDA 5-9; 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 glandular heron's bill can survive?

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

What hardiness zone is glandular heron's bill?

Glandular Heron's Bill is rated USDA 5-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can glandular heron's bill survive winter outside?

Plant it out within USDA 5-9 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 glandular 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.