Cold hardiness & minimum temperature

Is Nasturtium 'Empress of India' (Tropaeolum majus 'Empress of India')cold hardy? Hardiness zone & min temp

Also called Garden nasturtium, Indian cress.

More about nasturtium 'empress of india'

About Nasturtium 'Empress of India'

Tropaeolum majus 'Empress of India' · also called Garden nasturtium, Indian cress · edible

'Empress of India' is a compact, bushy nasturtium with deep blue-green leaves and vivid crimson-scarlet flowers. Both peppery leaves and flowers are edible, and it flowers best on poor soil in full sun. A fast, trouble-free hardy annual, it sows direct after frost, trails or mounds well in beds and pots, and self-seeds freely.

Cold limit: USDA 9-11 as a perennial; grown as a warm-season annual elsewhere · RHS H2 (15-28°C)

Watch for — Frost damage: Tender to frost and collapses at the first hard freeze. Sow only after the danger of frost has passed.

What nasturtium 'empress of india''s hardiness rating actually means

Hardiness works differently for nasturtium 'empress of india': 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 H2 means: Tender — survives a frost-free greenhouse or a very mild, sheltered spot. On the US scale that maps to USDA 9-11 as a perennial; grown as a warm-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 nasturtium 'empress of india' 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 nasturtium 'empress of india' 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 nasturtium 'empress of india' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H2 figure above.

Frost protection for borderline nasturtium 'empress of india'

Nasturtium 'Empress of India' 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.

Nasturtium 'Empress of India' hardiness — frequently asked questions

Is nasturtium 'empress of india' cold hardy?

Hardiness works differently for nasturtium 'empress of india': 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. Nasturtium 'Empress of India' is grown 9-11 as a perennial; grown as a warm-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 nasturtium 'empress of india' 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 nasturtium 'empress of india'?

Nasturtium 'Empress of India' is rated USDA 9-11 as a perennial; grown as a warm-season annual elsewhere and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can nasturtium 'empress of india' 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 nasturtium 'empress of india' 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.