UK hardiness
Is Zinnia haageana 'Old Mexico' hardy in the UK?
Zinnia haageana 'Old Mexico'
More about zinnia haageana 'old mexico' in the UK
Zinnia haageana 'Old Mexico' and the RHS hardiness rating
Zinnia haageana 'Old Mexico' is rated RHS H2 — tender, meaning it withstands winter minimums of about 1 to 5°C. In practice that means it needs a frost-free greenhouse or indoors over winter — a UK frost will kill it. The RHS rating describes an absolute minimum temperature, not an average: a single hard frost below its band is what does the damage, so the question is always "what is the coldest night my garden gets?", not "what is a typical winter here?".
This follows the RHS plant hardiness rating system (H1a–H7), the UK standard. For the US growing-zone view, see the zinnia haageana 'old mexico' USDA hardiness guide.
Does UK region change it?
Because zinnia haageana 'old mexico' is frost-tender, UK region matters less than the simple rule: it does not stay outdoors over winter anywhere in the UK. Treat any time outside as a summer holiday — bring it back indoors once nights drop toward 10°C, well before the first frost, and acclimatise it over a week each way so the leaves do not shock.
Overwintering zinnia haageana 'old mexico' in the UK
Overwintering zinnia haageana 'old mexico' in the UK means bringing it in: a bright, frost-free room or a heated glasshouse, watered sparingly while growth slows. Do not leave it against cold glass or near an unheated porch. Move it back out only after the last spring frost has passed for your area.
Zinnia haageana 'Old Mexico' UK hardiness — frequently asked questions
Is zinnia haageana 'old mexico' hardy in the UK?
Zinnia haageana 'Old Mexico' is rated RHS H2 (tender, hardy to about 1 to 5°C). It is not winter-hardy anywhere in the UK and must be overwintered under cover.
Can zinnia haageana 'old mexico' stay outside over winter in the UK?
No. Zinnia haageana 'Old Mexico' is frost-tender — a UK frost will kill it. Bring it indoors or into a frost-free greenhouse before the first autumn frost and return it outside only after the last spring frost.
What does RHS H2 mean?
RHS hardiness ratings run H1a (needs a heated glasshouse) to H7 (survives below -20°C). Zinnia haageana 'Old Mexico''s rating, H2, means tender — it tolerates winter minimums of about 1 to 5°C. The rating is an absolute minimum, not an average.
How do I overwinter zinnia haageana 'old mexico' in the UK?
Overwintering zinnia haageana 'old mexico' in the UK means bringing it in: a bright, frost-free room or a heated glasshouse, watered sparingly while growth slows. Do not leave it against cold glass or near an unheated porch. Move it back out only after the last spring frost has passed for your area.
Does UK region change whether zinnia haageana 'old mexico' survives?
Because zinnia haageana 'old mexico' is frost-tender, UK region matters less than the simple rule: it does not stay outdoors over winter anywhere in the UK. Treat any time outside as a summer holiday — bring it back indoors once nights drop toward 10°C, well before the first frost, and acclimatise it over a week each way so the leaves do not shock.
More zinnia haageana 'old mexico' care
See the full zinnia haageana 'old mexico' care guide, its temperature & humidity needs, and the US (USDA) hardiness version of this page.