Understanding citrus hardiness

What does the hardiness of a citrus tree mean?

Hardiness indicates the lowest temperature that a mature, healthy, properly acclimatised citrus tree can withstand during a brief frost. It is neither an ideal growing temperature nor an absolute guarantee of survival.

Why temperature alone is not enough

Actual resistance also depends on how long the frost lasts, on wind, humidity, the state of the soil, the stage of growth, the age of the plant and its rootstock. Short, dry cold is generally tolerated better than a prolonged frost with wind or waterlogged ground.

Young plants and container growing

The figures given apply to mature, acclimatised specimens. A young plant, a recently planted tree or a citrus grown in a pot must be protected sooner. In a pot the roots are far more exposed to cold than in open ground.

How to use the filter

Select the lowest temperature usually recorded in your garden. The filter shows the varieties rated for that temperature or lower. In an exposed position, or if in doubt, keep a safety margin of a few degrees.

The influence of the rootstock

The rootstock affects vigour and adaptation to the soil, and can also alter cold resistance. See our guide to choosing a rootstock.