Cold hardiness & minimum temperature

Is Nemesia strumosa 'Poetry Blue' (Nemesia strumosa 'Poetry Blue')cold hardy? Hardiness zone & min temp

Also called Poetry Blue Nemesia, Blue Cape Jewels.

More about nemesia strumosa 'poetry blue'

About Nemesia strumosa 'Poetry Blue'

Nemesia strumosa 'Poetry Blue' · also called Poetry Blue Nemesia, Blue Cape Jewels · flowering

'Poetry Blue' is a compact South African Nemesia bearing masses of small two-lipped lavender-blue flowers over bushy foliage from late spring through summer. A cool-season bedding and container favourite, it flowers best in mild weather, likes sun with even moisture and rich soil, and reblooms strongly if trimmed back when the first flush tires.

Cold limit: USDA 9-10 (grown as a frost-tender cool-season annual in most US zones) · RHS H3 (10-24°C)

What nemesia strumosa 'poetry blue''s hardiness rating actually means

Hardiness works differently for nemesia strumosa 'poetry blue': 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 9-10 (grown as a frost-tender cool-season annual in most US zones) — 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 nemesia strumosa 'poetry blue' 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 nemesia strumosa 'poetry blue' 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 nemesia strumosa 'poetry blue' 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 nemesia strumosa 'poetry blue'

Nemesia strumosa 'Poetry Blue' 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.

Nemesia strumosa 'Poetry Blue' hardiness — frequently asked questions

Is nemesia strumosa 'poetry blue' cold hardy?

Hardiness works differently for nemesia strumosa 'poetry blue': 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. Nemesia strumosa 'Poetry Blue' is grown 9-10 (grown as a frost-tender cool-season annual in most US zones); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature nemesia strumosa 'poetry blue' 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 nemesia strumosa 'poetry blue'?

Nemesia strumosa 'Poetry Blue' is rated USDA 9-10 (grown as a frost-tender cool-season annual in most US zones) and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can nemesia strumosa 'poetry blue' 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 nemesia strumosa 'poetry blue' 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.