Growing citron trees

The citron develops into a small tree with thorny branches. It is planted in spring, in March-April, when temperatures rise. There are a few varieties appreciated by collectors, such as Citrus medica ‘Pigmentata’, blood-red and highly aromatic, and Citrus medica ‘Maxima’, which has particularly large fruits.

Citrus medica ‘Maxima’ and ‘Pigmentata’

Its planting in open ground is only possible in an area spared from frost, such as USDA zone 9b, along the Mediterranean coastal strip, as it is very sensitive to frost, tolerating only brief frosts below -3° C.

Elsewhere, it is grown in pots outdoors and brought indoors for the cold season.

Choose a warm, sunny location for its cultivation, but not scorching, sheltered from winds and sea spray. It fears drought and scorching sun.

The citron, like other citrus trees, needs rich, fertile, light, and well-draining soil. It dislikes limestone and is best grown in neutral to acidic pH soil.

To plant a citron tree, whether in the ground or in a pot, you will need sand, compost, fertiliser, as well as potting soil, drainage for the bottom of the planting hole or pot, and organic mulch to keep its base cool.

Planting in the ground

1. Soak the root ball in a bucket of water for about ten minutes to allow it to rehydrate properly.
2. Dig a planting hole approximately 2 to 3 times the size of the root ball.
3. Mix your soil with well-decomposed compost, river sand, and possibly potting soil. Feel free to also add a special citrus fertiliser, preferably organic.
4. Install a layer of drainage at the bottom of the planting hole (gravel, pumice, clay balls, etc.).
5. Add a portion of your soil mixture.
6. Place the root ball in the centre of the hole, adding your mixture until the roots are covered, but without burying the grafting point (a sort of bulge at the base of the trunk).
7. Firm the soil.
8. Form a wide basin around the base of your citron tree to retain watering water effectively.
9. Water generously.
10. Mulch carefully to limit water evaporation and space out watering.

Adult citron trees in the ground[/caption>

Planting in a pot

Choose a container 2 to 3 times larger than the root ball, such as a terracotta pot or a wooden box, which must be drilled or can be drilled by you, to prevent the roots from stagnating in water.

Use a special citrus potting soil or create a substrate consisting of 50% potting soil, 30% compost, and 20% sand.

1. Soak the root ball in a bucket of water for about ten minutes to allow it to rehydrate and facilitate the removal from the nursery pot.
2. Place a layer of drainage at the bottom of the pot using clay balls or gravel a few centimetres thick (pumice is heavier and should be avoided in pots).
3. Pour the potting soil or mixed substrate until about halfway up the pot. You can also add a special citrus fertiliser.
4. Remove the nursery pot and loosen the roots at the bottom of the root ball.
5. Place your citron tree in the pot.
6. Fill in with your substrate without burying the collar.
7. Firm the soil.
8. Water generously.
9. Mulch carefully to a thickness of several centimetres.

The care of the citron is summarised in two main areas: watering and fertilisation.

Outdoor cultivation

Water regularly during the first few years, allowing the citrus to develop its root system. Afterwards, water mainly during dry periods, preferably using rainwater. Plan to water once a week in summer, more often in case of prolonged drought. Reduce watering in autumn, then stop or significantly reduce it in winter (adjust according to winter rainfall). Mulch around the base, as this helps to keep the soil cool for longer while limiting weed growth. Place dead leaves or organic mulch around the trunk.

Apply organic fertiliser or well-decomposed compost to nourish the bush.

In autumn, when temperatures cool, you can place a fleece over the aerial parts to protect the fruits, which are more sensitive to frost.

Pot cultivation

Water regularly from spring to autumn, providing water as soon as the substrate becomes dry (watering once or twice a week). Use rainwater whenever possible. Avoid letting water stagnate in the saucer. The citron is nutrient-hungry, so apply liquid fertiliser about once a month. You can also use slow-release fertiliser. In winter, reduce watering and fertiliser applications.

In autumn, around October, bring it into a frost-free shelter, such as a cold greenhouse or a conservatory. Choose a bright but unheated location: ideally, the temperature should be between 7 and 10 °C. In spring, take your bush back outside, placing it in a sunny spot.

Repot your citron approximately every two years, preferably in spring. This way, you renew its substrate and provide more space for its roots and growth. In years when you do not repot, perform a top dressing: remove the surface substrate by a few centimetres and replace it with fresh potting soil.