Bitter orange: care, flowering & use of Seville oranges

The bitter orange, also called Seville orange, is a hybrid citrus plant. Below you will find tips on cultivation, care and use of the exotic plant.

Exotic citrus plants are very popular in this country. But while lemons and oranges are increasingly cultivated, bitter orange is rarely found. Here you will find a short profile of this special plant, as well as some tips on cultivation, proper care and use of the bright orange fruits.

Bitter orange: flowering time, origin and characteristics

The bitter orange (Citrus x aurantium) is a hybrid of the grapefruit (Citrus maxima) and the mandarin (Citrus reticulata) that has been cultivated in the Mediterranean region since the 10th century. The evergreen plant probably originated in the tropical Himalayan region of southern China, from where it was brought to Italy. Some also know it by the names of bigarade orange, Seville orange or marmalade orange. It belongs to the citrus genus (Citrus) and thus to the rue family (Rutaceae).

If the climatic conditions are right for the heat-loving bitter orange, it can grow into a tree up to 10 metres tall. Depending on the variety, the forks of older branches, may be studded with thin, short thorns. Younger branches usually bear long thorns. The leaves are rich green, oval shaped and form a 2 to 3 cm long petiole. A distinctive feature of the leaves are the oil glands from which the pleasantly fragrant essential oil petitgrain is released.

The white bitter orange flowers have a strong fragrance and are formed mainly between May and June. It is not uncommon for the blossoms to be spread over the rest of the year so that blossoms and fruits adorn the tree at the same time. The fruits are ready for harvesting after about eight months. The fruits resemble those of the orange (Citrus × sinensis) but are much smaller, irregularly shaped, and have a bitter taste. When the fruits are ripe, the thick skin glows a vibrant orange. The pulp is very sour compared to oranges and the white skin of the fruit tastes extremely bitter.

Risk of confusion: The Seville orange may be confused with Poncirus trifoliata (trifoliate orange or Japanese orange) because of the homonymously used name “bitter orange”. Although both plants belong to the rue family, bitter orange belongs to the Citrus genus, while trifoliate orange belongs to the Poncirus genus. While the bitter orange is not hardy, the deciduous trifoliate orange can be overwintered outdoors. The leaves and fruits of the two plants are visually different from each other. Moreover, the fruits of the trifoliate orange are inedible unlike those of the bitter orange.

The best varieties

There are many varieties of bitter orange. The economically most important and popular varieties include:

• Chinotto variety group: Citrus aurantium var. myrtifolia; group of cultivars used in Italy for many digestifs; usually small, slow-growing shrubs; no spines; relatively small fruits; cultivars: ‘Boxwood Leaf Chinotto’, ‘Crispifolia’, ‘Dwarf Chinotto’ or ‘Large Chinotto’.
• German Landsknechthose: Citrus aurantium fasciata; a group of varieties cultivated in Germany since the 16th century; forms orange fruit with light orange stripes that are reminiscent of “Knechtshosen”; cultivars: ‘Virgatum’, ‘Virgolare’ and ‘Fiamato’.
• ‘Consolei’: Forms a compact crown without thorns; rounder leaves and large flowers; furrowed appearance due to same-coloured ridges on fruits; strong fruit set.
• ‘Salicifolia’: Narrow, willow-like leaves with an irregularly wavy edge; thornless, dense crown; uniformly round fruits.
• ‘Foetifera’: Forms flattened fruits with daughter fruit (main fruit with enclosed second fruit); cultivated for a long time; spreading growth of the tree.

Planting bitter oranges: how to do it

Owing to its Mediterranean origin, the bitter orange tree is particularly dependent on warm, dry temperatures. High humidity also increases the risk of fungal infection. The best place for bitter oranges is a bright location without drafts, whereby direct sun is not a problem either. During the warm summer, the trees can be placed in the garden but in winter they should move to a mild winter area. As a potted plant, the bitter orange usually does not grow taller than two metres, which makes it a little easier to move between summer and winter locations.

High-quality universal soil is suitable as a plant substrate, which is mixed with 1/3 expanded clay for better ventilation. This will save you from buying a special soil, which is usually expensive. It is also important for citrus plants to use soil with a slightly acidic pH to allow healthy growth. Our Plantura Organic All Purpose Compost, for example, meets the requirements of citrus plants and is also produced without peat to protect the environment. In addition, the soil can still be covered with an acidifying material, such as pine bark. This maintains the slightly acidic pH of the soil, protects against fungus gnat infestation and also looks nice.

Since citrus plants do not like to be repotted, the opportunity should be taken to provide the plants with long-term nutrients with a fertiliser. Our Plantura Flower Food in granulate form offers the possibility to create such a fertiliser depot. Thanks to its balanced NPK ratio, it strengthens the citrus plant in the long term and ensures vigorous growth of roots, leaves and fruits.

Seville orange care

If the location requirements of the bitter orange are met, it is a fairly undemanding plant that also thrives with little care.

Watering and fertilising bitter oranges

During vegetation, it is important to water the plant regularly as it requires a lot of water. The root ball should not dry out, but also should not be exposed to waterlogging. Bitter oranges should not be watered during the hot midday hours, as this is when a lot of water evaporates and does not reach the plant. It is best to water either early in the morning or late in the evening. For bitter oranges it is important to water with low-lime water, otherwise the soil pH may increase, affecting growth. Collected rainwater or mineral water are suitable.

At the latest when the first leaves turn a light green colour, it is time for fertilisation. Yellow leaves are almost like a cry for help since this is how an iron deficiency manifests itself. To prevent this, fertilise once a week with a fertiliser specifically adapted to the needs of citrus plants. Our Plantura Liquid Citrus Food is perfectly suited for this purpose: it promotes vigorous plant growth and provides the bitter orange with all the essential nutrients for the ripening of aromatic fruits.

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Pruning

The Seville orange tree should be cut back once a year to bring the plant into shape. The best time to do this is in the spring before the start of vegetation, as this is when pruning cuts heal best. Young plants develop a compact crown after about 2 to 3 years. If you are not satisfied with the shape of the bitter orange tree, you can prune it back much more. The plant then begins to sprout new shoots on the remaining branches and can be brought back into shape. This is also an option for plants that have grown too large to make the bitter orange a little more compact again.

Bitter orange tree does not bloom: what can be done?

If the bitter orange does not bloom, it is usually due to a too humid winter. If the plant is watered too often or too heavily in its winter quarters, the fine roots die and the plant may be insufficiently supplied with water and nutrients. When it has come to this, the bitter orange should not be watered for a long time so that the root ball can dry out and new fine roots can be formed. Sometimes, citrus plants can be encouraged to flower by a drought stimulus. To take advantage of this, you can completely dispense with watering after the first flowering of the year or the throughput of spring. If the leaves begin to droop, they should not be watered for another week. After that, watering can continue as normal and, with a little luck, the tree will begin to bloom.

Propagating Seville oranges

You can propagate bitter oranges through the seeds contained in the fruit. The seeds can be taken from the fruits and placed in a pot with potting soil, such as our Plantura Organic Herb & Seedling Compost. They should sit about an inch deep in the soil and be kept moist by repeated watering. Subsequently, a lid or cling film can be used to create a microclimate that ensures rapid germination. In a warm place, the first seedlings can be seen after just a few weeks. From time to time, the lid should be opened to prevent mould growth. The first flowers of the homegrown bitter orange tree will appear only after 8-10 years of growth, as well as the first fruits.

Is the bitter orange tree hardy?

Bitter oranges are not hardy. Temperatures as low as -5 °C are tolerated for a short time, but damage the plant for a longer period of time. You should therefore move it to mild winter quarters during the cold months It makes little demands on the winter quarters, but it should be as bright as possible. The ideal temperature is 5 to 10 °C; higher temperatures are possible in suitably bright rooms such as a conservatory. The bitter orange should be moved to its winter quarters before the first frost. If the temperature is consistently above 10 °C again in spring and frost-free at night, it can move back outdoors.

During the winter dormancy, the bitter orange should only be watered moderately, as if too wet the fine roots die and the plant will otherwise not bloom for the next year. A finger test can be used to determine whether the soil is still moist enough or whether it needs to be watered. Fertilisation is not necessary during the winter dormancy.

Harvesting and using bitter oranges

Due to the change of seasons, citrus plants in our country bloom more in the spring and summer; accordingly, the fruits ripen after eight months between November and the following spring (March to May). However, the harvest is only successful if the bitter orange can be offered warm, light winter storage, otherwise ripening will be greatly delayed or even won’t take place at all.

The use of the bitter orange is varied as all parts of the fruit are edible. The peel is often used for the production of candied orange peel. The famous Curacao liqueur or jam with pulp is made from peel and juice. The juice can be drunk in the form of bitter orange lemonade, and the flowers make orange blossom water or tea. The essential oils of the peel are a component of many perfumes or serve as room fragrances.