How to choose your cold risk profile

Our cold maps offer five risk profiles, from the most cautious to the boldest. This page explains what each one means and how to choose yours according to your project.

Why a risk profile?

Standard hardiness maps, such as the USDA zones, show the 30-year average of the coldest night of each winter. They are reassuring, but misleading: a citrus tree does not die of an average, it dies of the coldest night it goes through. About one winter in three drops below that average, and a single harsh winter can be enough to lose a tree.

There are many ways to sum up on a map the cold of a place, which changes from one winter to the next: the hardest frost of the last 30 winters, the average of the 30 winters, the average of the 3 coldest winters, the cold that comes back one winter in ten… Each one gives a different figure for the same garden.

To keep things simple, we offer five of these ways of calculating, and we have named them after the risk you are willing to take:

  • Conservative: the hardest frost of the last 30 winters.
  • Cautious: the cold reached or exceeded about 1 winter in 10. This is the default setting of our maps.
  • Normal: the cold reached or exceeded 1 winter in 5.
  • Gambler: the average of the 30 winters, the method of the USDA zones.
  • Daredevil: the average of the last 5 winters only.

Choosing according to your project

You are planting an orchard to sell your fruit

A farmer diversifying into citrus commits each tree for twenty years. For them, it is not enough for the tree to survive: the crop has to sell. An early frost, in autumn or early winter, damages the fruit still on the tree before it has reached the sugar level the market expects. A late frost, in spring, destroys the flowers and young shoots, and with them the next crop. A dead tree leaves a gap in the row, and a frozen or overly acidic crop means a year without income.

Recommended profile: Conservative or Cautious.

  • Also look at the frost dates for your town: how late it freezes at −2 °C in spring (flowers), how early it freezes at −5 °C in autumn (fruit). See the cold in your town.
  • Where it still freezes in late April, a rootstock that delays bud break, such as Poncirus, protects the blossom.
  • Where frost arrives in November, choose early-ripening varieties such as satsumas, or pick before the first hard frosts.

You want to enjoy your garden

For a home gardener planting a few citrus trees, losing a variety now and then is no disaster. A good harvest every two or three years is already a success, and slightly less sweet fruit still makes excellent marmalade.

Possible profile: Gambler, or even Daredevil.

  • Choose the exact spot to gain a few degrees: against a south-facing wall, in a corner sheltered from the wind, away from hollows where cold air collects.
  • Cover the plant with a winter fleece on frosty nights when the winter is harsher than usual.
  • The rule of our maps: without protection if the variety's hardiness goes at least as low as the cold of your profile; with a fleece if it falls short by 3 °C at most; otherwise in a pot, brought in for the winter.

If in doubt, choose Cautious: the cold that comes back about one winter in ten.

What the hardiness on a product page means

The hardiness given on our product pages is a survival threshold: the lowest temperature a mature, healthy, acclimatised citrus can withstand during an occasional frost. Below it, the tree dies. Damage starts well before:

  • flowers and young shoots freeze at around −2 °C: the next crop is lost, not the tree;
  • fruit still on the tree is damaged at around −5 °C;
  • then the leaves are scorched and the current year's shoots dry out;
  • the trunk and roots are only reached close to the hardiness on the product page.

So compare the hardiness on a product page with the cold of your profile, never with the cold of an average winter. To find out more: Understanding citrus hardiness.

An example: Toulouse

Each winter, we keep its coldest night. The curve gives the % of the 30 winters that went down to this temperature or lower. Each profile is a point on this curve: the further left, the more cautious.

0 %20 %40 %60 %80 %100 %CautiousNormal−14 °C−13 °C−12 °C−11 °C−10 °C−9 °C−8 °C−7 °C−6 °C−5 °C−4 °C−3 °C−2 °C−1 °Ccoldest night of the winter →% of wintersConservative · −12 °C (−12.3 °C)Cautious · −9 °C (−8.8 °C)Normal · −7 °C (−7.5 °C)Gambler · −6 °CDaredevil · −6 °C

What each profile means in Toulouse

  • By choosing a Conservative profile to pick a variety, you take into account the hardest frost of the last 30 winters: −12 °C. In 30 years, no winter has gone lower.
  • By choosing a Cautious profile to set the minimum for your area (−9 °C), you run the risk of losing a plant hardy to −9 °C 3 winters in 30 (about 1 winter in 10).
  • By choosing a Normal profile (−7 °C), you run the risk of losing a plant hardy to −7 °C 6 winters in 30 (about 1 winter in 5).
  • By relying on the USDA maps (Gambler profile) to set the minimum for your area (−6 °C), you run the risk of losing a plant hardy to −6 °C 15 winters in 30 (one winter in two).
  • By relying on the last 5 winters only (Daredevil profile, −6 °C), you run the risk of losing a plant hardy to −6 °C 15 winters in 30 (one winter in two).

Where these figures come from

The last 30 winters (1996-1997 to 2025-2026) from Météo-France stations, day by day. For a town: the 5 nearest stations within 40 km, weighted by distance, and 0.5 °C less per 100 m when the town is higher than the station. The Cautious profile is our own calculation. It is very close to the "10-year" cold (the cold that comes back once in ten years) given by the method used by weather services, the Gumbel distribution, which we applied to the same records. The details: our method.

See the cold in your town → · The cold map →

Weather stations used for Toulouse: Toulouse-Blagnac, Toulouse-Francazal, Auzeville-Tolosane (INRAE), Ondes, Muret-Lherm. Source: Météo-France, daily data (data.gouv.fr, Licence Ouverte 2.0), winters 1996-1997 to 2025-2026.

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