Frequently asked questions
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Citrus resistance levels depend on species and variety.
Table on page Hardy Citrus page shows observed resistance levels for mature trees.
During the first few years of growth, the trees are not yet fully established. They will only reach the indicated level of hardiness after three to four years in the ground.
It is therefore important to be ready to protect young trees during this period to avoid any accidents.
Non-woven fabric (NWF) is commercially available in rolls up to 10m wide. It is commonly used by horticulturists in the spring as a forcing veil for vegetables. It is a synthetic fabric, for which there is no natural alternative yet. It allows light, rain and air to filter through while providing thermal gain.
Lay the TNT veil in a bell shape over the tree on three or four sticks. The veil must not pinch the foliage so as not to burn it.
A square of around 5 x 5m can be used to create the bell on sticks 1.5 to 1.8m high. In windy conditions, the ends need to be secured to the ground with stones.
A grammage of 17gr to 19gr per m² is generally sufficient. If a very intense and prolonged cold is forecast, two overlapping veils can be applied.
In theory, a simple veil can save two or three degrees.
However, this is not borne out by our practical experience. With minimum-maximum thermometers installed under the veil and outside, we observed the same minimum temperatures in 2022 (-7 degrees C at night). Maximum temperatures, on the other hand, were much higher under the sail (sometimes over 10 degrees C).
On this basis, our recommendation is to install the sails during the winter only in the event of a very intense or fairly long cold snap (two days or more). Leaving the sails in place all winter could increase the temperature difference between day and night, and thus the risk of thermal shock.
Whether or not combined with non-woven fabric (TNT), plant mulch will generate heat. This allows a few degrees of heat gain at the base of the tree and under the crown. See the Watering chapter for full details on mulching methods.
If an intense cold snap is forecast, install a mulch or reinforce the existing one before laying a TNT fleece.
Mulching should be installed or renewed before winter, in November. Dry hay, or hay already in the process of decomposing, is ideal, to a thickness of 20-30cm and a diameter of 50cm in a circle around the tree.
Protective sails can êon trees less than three years old from December to the end of February, in the event of an intense or long-lasting cold snap. After these exceptional events, we recommend removing the sails.
Installing fixed sails throughout the winter is not recommended, as it presents a number of risks.
Firstly, the accentuation of temperature differences between day and night, especially during long sunny spells in winter, can cause irreparable thermal shock.
Secondly, the early warming of trees under canopies can trigger an early and rapid vegetative awakening (as early as February), making them extremely vulnerable to the slightest frost.
These negative effects are more pronounced with thicker sails.
For mature trees, very large sails are required.
They will only be installed in the event of a severe and prolonged frost warning.
It is advisable to remove them as soon as night-time temperatures return to positive.
Citrus trees have flexible branches and can withstand a few inches of snow without damage. Beyond that, it is advisable to shake the branches to lighten them and prevent them from breaking.
If you have laid a bell-shaped NWF veil, the snow will slide over it and accumulate all around.
If the branches are covered with ice, it will have a protective effect, maintaining a temperature around -2 C on the branches.
Young shoots can suffer and burn in heavy frosts.
The last fall growth, from October to November depending on the weather, will be particularly vulnerable. The shoots will bend and then mend, turning brown and then black.
This is of no consequence to the tree, as the wood of the trunk and main branches provides the strength.
However, all damaged ends should be pruned at the end of winter, in the second half of March. In April and May the pruned secondary branches will regenerate quickly. Growth will even be accelerated, provided the tree is well fed in early spring.
