Cold hardiness & minimum temperature

Is Antirrhinum majus 'Rocket Red' (Antirrhinum majus 'Rocket Red')cold hardy? Hardiness zone & min temp

Also called Rocket Red Snapdragon, Tall Red Snapdragon.

More about antirrhinum majus 'rocket red'

About Antirrhinum majus 'Rocket Red'

Antirrhinum majus 'Rocket Red' · also called Rocket Red Snapdragon, Tall Red Snapdragon · flowering

A tall, heat-tolerant snapdragon series bred for long, strong flower spikes that make excellent cut flowers. 'Rocket Red' produces dense columns of rich red dragon-mouth blooms on stems reaching well over half a metre. It thrives in cool-to-mild conditions, performs as a cool-season annual, and rewards deadheading with repeat flushes.

Cold limit: USDA 7-11 (perennial in mild zones, grown as a cool-season annual elsewhere) · RHS H3 (10-24°C)

Watch for — Bloom stall in summer heat: Snapdragons slow or stop flowering above roughly 26°C. Deadhead, keep them watered, and expect a renewed flush as temperatures cool.

What antirrhinum majus 'rocket red''s hardiness rating actually means

Hardiness works differently for antirrhinum majus 'rocket red': 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 H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA 7-11 (perennial in mild zones, grown as a cool-season annual elsewhere) — 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 antirrhinum majus 'rocket red' 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 antirrhinum majus 'rocket red' 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 antirrhinum majus 'rocket red' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline antirrhinum majus 'rocket red'

Antirrhinum majus 'Rocket Red' 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.

Antirrhinum majus 'Rocket Red' hardiness — frequently asked questions

Is antirrhinum majus 'rocket red' cold hardy?

Hardiness works differently for antirrhinum majus 'rocket red': 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. Antirrhinum majus 'Rocket Red' is grown 7-11 (perennial in mild zones, grown as a cool-season annual elsewhere); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature antirrhinum majus 'rocket red' 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 antirrhinum majus 'rocket red'?

Antirrhinum majus 'Rocket Red' is rated USDA 7-11 (perennial in mild zones, grown as a cool-season annual elsewhere) and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can antirrhinum majus 'rocket red' 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 antirrhinum majus 'rocket red' 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.