Cold hardiness & minimum temperature

Is Forking larkspur (Consolida regalis)cold hardy? Hardiness zone & min temp

Also called Forking larkspur, Royal larkspur, Field larkspur.

More about forking larkspur

About Forking larkspur

Consolida regalis · also called Forking larkspur, Royal larkspur · flowering

Forking larkspur is a delicate, branching annual native to European meadows and arable land, producing airy sprays of small violet-blue or white spurred flowers with distinctive forked stems. Lighter and more open in habit than Consolida ajacis, it brings an effortless meadow aesthetic to borders and cut-flower arrangements. Thrives in cool weather and lean, well-drained soil.

Cold limit: USDA 2–10 (cool-season annual) · RHS H6 (5–18°C)

Watch for — Early termination in summer heat: Forking larkspur is even more heat-sensitive than Consolida ajacis. Plants yellow, set seed, and die quickly when temperatures rise above 20°C. Sow in autumn for spring bloom or as early in spring as possible to maximise the cool-season window.

What forking larkspur's hardiness rating actually means

Hardiness works differently for forking larkspur: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". Its RHS rating of H6 means: Hardy throughout the UK and northern Europe. On the US scale that maps to USDA 2–10 (cool-season 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

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

Concretely, for forking larkspur as it gets too cold:

Light frost (around 0 to −2 °C) damages or kills tender summer crops outright; cold-hardy types take a few degrees of frost.
The plant does not "survive winter" — its life cycle simply ends, by design, when frost arrives or it finishes cropping.
A surprise late spring frost can also kill young transplants set out too early, before the season even starts.

Can forking larkspur go outside or overwinter — and where?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost.
In short-season zones, start it indoors or under cover to stretch the effective growing window.
Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

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 forking larkspur can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Frost protection for borderline forking larkspur

Forking larkspur is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks.
Have row cover ready for an unexpected late spring or early autumn frost.
Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.

Forking larkspur hardiness — frequently asked questions

Is forking larkspur cold hardy?

Hardiness works differently for forking larkspur: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". A seasonal crop, not a perennial. Forking larkspur is grown 2–10 (cool-season annual); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature forking larkspur can survive?

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

What hardiness zone is forking larkspur?

Forking larkspur is rated USDA 2–10 (cool-season annual) and RHS H6 — Hardy throughout the UK and northern Europe.

Can forking larkspur survive winter outside?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost. In short-season zones, start it indoors or under cover to stretch the effective growing window. Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

How do I protect forking larkspur from frost?

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks. Have row cover ready for an unexpected late spring or early autumn frost. Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.