Cold hardiness & minimum temperature

Is Fernleaf Dill (Anethum graveolens 'Fernleaf')cold hardy? Hardiness zone & min temp

Also called Fernleaf Dill, Dwarf Dill.

More about fernleaf dill

About Fernleaf Dill

Anethum graveolens 'Fernleaf' · also called Fernleaf Dill, Dwarf Dill · herb

An All-America Selections winner and compact dwarf dill cultivar reaching just 30–45 cm tall, ideal for containers, window boxes, and small gardens. Features finely textured, feathery blue-green foliage with strong dill flavour. Slower to bolt than standard tall varieties, providing an extended leaf harvest season.

Cold limit: USDA 2-11 (annual) · RHS H4 (10–26°C)

Watch for — Bolting in high heat: Sustained temperatures above 26°C trigger premature flowering, ending the leaf harvest. Provide afternoon shade, sow in early spring or late summer, and harvest regularly to delay flowering.

What fernleaf dill's hardiness rating actually means

Yes — fernleaf dill is genuinely cold hardy. Rated RHS H4 and USDA 2-11 (annual), 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 2-11 (annual) — 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. Fernleaf Dill is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for fernleaf dill 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 fernleaf dill go outside or overwinter — and where?

Plant it out within USDA 2-11 (annual) 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 fernleaf dill can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Fernleaf Dill hardiness — frequently asked questions

Is fernleaf dill cold hardy?

Yes — fernleaf dill is genuinely cold hardy. Rated RHS H4 and USDA 2-11 (annual), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Fernleaf Dill is hardy across USDA 2-11 (annual); 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 fernleaf dill can survive?

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

What hardiness zone is fernleaf dill?

Fernleaf Dill is rated USDA 2-11 (annual) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can fernleaf dill survive winter outside?

Plant it out within USDA 2-11 (annual) 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 fernleaf dill 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.