Hardy citrus
Cold resistant citrus
The citrus trees for sale on this site are all cold resistant, from -8 C to -16 C for the most rustic.
The rootstocks used offer the best combination of frost resistance and vigor.
The grafts were taken from mother trees that have endured intense outdoor cold waves, most of them from nurseries or farmers, sometimes from private gardens. Their selection is the result of meticulous observations throughout the decades, by gardeners with an attentive eye, but also of multiple exchanges between enthusiasts. All these mother trees were grown in the open ground, with a good exposure, protected from strong winds, well fed and irrigated.
The hardiness levels remain indicative and apply to adult trees in dormancy in the middle of winter, in a sheltered situation.
Cold hardiness of adult trees
The USDA (U.S. Department of Agriculture) climate zones indicate the thermal minima observed over the last 30 years.
The climate zones in Switzerland range from 5a (coldest) to 9a (warmest).
Hardiness levels are indicated for mature trees in open soil and wind-protected situations, for intense but brief frosts (a few nights).
It is the wood, the trunk and the main branches, that guarantees resistance to extreme cold.
Trees subjected to prolonged deep frost can suffer damage to young shoots.
In this case it is necessary to prune just before spring the small damaged branches, they will be regenerated with the first growth in April-May.
An exceptional cold snap is always possible, with lesions on the secondary branches.
A more drastic pruning will then be required for a good restart.
For young trees, when heavy frosts are forecast, add or reinforce mulch and lay a non-woven fabric veil.
Be careful not to let the veil touch the leaves, install it on 4 sticks planted around the young tree.
USDA climate zones in Switzerland
To find out which varieties you can plant in your area, first check your USDA climate zone
To find the nearest city, please visit the site:
https://www.plantmaps.com/interactive-switzerland-plant-hardiness-zone-map-celsius.php
The interactive map allows you to zoom in on your town and identify the USDA climate zone of the planned planting.
For a detailed view of thermal minima measured since 1991, please consult the following link:
Weather Switzerland – Temperature
Click on the nearest weather station to access the data by selecting “Comparison with climatic data”.
USDA climate zones are defined by the minimum temperatures reached during the year (usually in January or February).
However, within a given region, minimum temperatures can change significantly, sometimes within a few kilometers or even only a few hundred meters away.
Factors that positively influence thermal minima include:
- The orientation of the land
A southern exposure strongly attenuates the minima and their duration
- Wind protection
A sheltered area will gain in heat, extreme cold will be shorter
- The presence of a lake
A body of water, if large enough, will dampen and shorten cold spells.
- The urban environment
In the city and suburbs, the urban bubble effect reduces nighttime lows by several degrees in winter.
These factors can combine to create 8a/8b (-12.2 C to -6.7 C) islands in the heart of a 7a/7b region (-17.8 C to -12.2 C).
To guarantee an optimal growth to a citrus tree it is necessary to install it in a place sheltered from the wind, well exposed to the sun especially in the morning.
You can plant near a house without fear, the main root of a citrus tree will plunge vertically into the ground. No risk for the foundations. The horizontal surface roots are not penetrating. The heat radiated by the walls will make you gain several degrees.
A dense hedge or a perimeter wall will also have a moderating effect on the extremes.
If you are planting in an orchard, do not space the trees too far apart.
Check the recommended planting distance in the description of the citrus fruit of your choice.
A citrus tree will only express its full potential if it is planted in the ground.
If the minimum temperatures in your region do not allow it for the varieties you have chosen, you will have to keep them in pots.
Trees will lose some of their hardiness by staying in a pot. In a classic pot, with rigid walls, the roots are concentrated against these walls and will be very exposed to frost.
In an Air-Pot, the roots are distributed throughout the volume and will be more protected. In this case, the loss of resistance to cold can be estimated at 5 to 6 degrees.
The best solution is to shelter them in winter in a greenhouse maintained between a minimum of -5 degrees (at night) and a maximum of +10 to +15 degrees (during the day), then take them out in spring.
Alternatively, surround the pot with a double layer of thick jute. Add thick mulch to the soil around the pot. If the size of the tree allows it, apply a TNT veil of 19gr/m2 (minimum) without sticking it on the leaves. Use 4 sticks to build a box around the plant, keep the veil on the ground with large rocks or bricks.
All the trees sold on this site are raised in Air-Pots (
see the manufacturer's website
), specially shaped pots that guarantee the integrity of the roots in the long term.
As the tree grows, it should be transplanted to a larger Air-Pot. In theory there is no limit to the size of the Air-Pots, the system being designed to be expandable. In practice, it will become difficult to move the trees quickly because of their weight. A reduction pruning each year will therefore be unavoidable, unless you can plant directly in the greenhouse.
Note:
Don't throw the Air-Pots away. You can reuse them or return them to us.
How to choose your citrus tree on AlpAgrumi.ch
- First, check what your USDA climate zone is.
See above:
USDA climate zones in Switzerland
] Map of USDA climate zones in Switzerland
- Are the conditions at the local level rather favorable ?
If you live in a valley, is it the sunny or shady side?
On the plain, are you sheltered by hills, by a forest?
Is there a lake nearby?
See above:
Local conditions and micro-climates - Do you have a protected place to plant?
Can you plant near a house, a wall, behind a hedge?
While ensuring that your tree gets plenty of sunlight, especially in the morning?
See above:
Good places to plant
- See the list of citrus fruits on this page.
Choisissez les arbres compatibles avec vos conditions climatiques locales.
Don’t forget to consider also the type of soil and therefore the most adapted rootstock. See Rootstocks - Visit our
eShop
to order and choose between Shipping and Pickup.
If you pick up your trees at the Monte-Carasso (Bellinzona) store, please remember to
book your appointment
