Sweet Orange – Citrus sinensis

Common Names: Sweet Orange, Orange, Citrus, Citrus sinensis, China Orange, Portugal Orange, Naranja (Spanish), Arancia (Italian), Sinaasappel (Dutch), Apelsin (Russian), Apelsin (Swedish), Apelsin (German), Portocal (Romanian), Dalandan (Filipino), International: Sweet Orange, Latin: Citrus sinensis, Origin: China

Latin Name: Citrus sinensis

Origin: Asia, Europe, South America, North America

Short Introduction

Seedlings of sweet orange do not retain the cultivated traits of the previous generation, so new trees are propagated by grafting desired cultivars onto rootstocks. The choice of rootstock impacts the growth rate, resilience, productivity, and fruit qualities of the plant. Grafted orange trees are transplanted to a permanent site the following year.

The soil should be well-aerated, well-drained, deep, and unsalinized for optimal growth. The ideal location maintains an average annual temperature of 21°C, with daily temperatures from +5°C to +35°C. Mature trees can briefly survive subzero temperatures, but the fruit cannot. Improper temperatures during ripening can lead to green or brown fruit.

For maximum productivity, sweet oranges are grown in plantations, typically spaced at 7.5 × 7.5 meters. Trees in such settings begin producing fruit at 3 to 5 years old, and are pruned, fertilized, cared for, and irrigated as needed. Vigorous, free-growing sweet orange trees in the Mediterranean can produce up to 3,000 fruits per year, whereas plantation trees yield about 300. From plantations, 130 to 160 tons can be harvested per hectare, with the average fruit weighing 0.3 kg. Ripe fruit is still harvested by hand today.

Detailed Description

A medicinal plant celebrated for its excellent fruit.

Botanical Information

Sweet orange is an evergreen tree reaching up to 15 meters tall, with a regularly branched, rounded crown. Young twigs often have angular, slender, and sharp thorns. The branches are covered with alternate, leathery, pointed, dark green leaves 7–15 cm long and 3–8 cm wide, with winged petioles.

The sweet orange’s flowers are bisexual, white, aromatic, and have five sepals. They are 2–3 cm in size and appear singly or in groups of up to six at the ends of branches, arranged in a cyme. They are pollinated primarily by insects, especially bees.

The fruit is a spherical hesperidium berry up to 10 cm in diameter, maturing after nine months. The outer layer is orange or yellow with aromatic glands. The endocarp consists of 10–14 segments of wedge-shaped, membranous sacs filled with sweet pulp. Depending on variety, the pulp can be yellow, orange, or deep red. Each segment may contain 2–4 irregular seeds, which remain viable for up to six months.

Origin and Distribution

Sweet orange (Citrus sinensis) most likely originated in southwestern China and northeastern India. It was introduced to Europe in the 15th century by either Italian or Portuguese navigators.

Since then, it has been cultivated in subtropical climates, especially around the Mediterranean, initially for its medicinal properties and later for its flavorful fruit.

Usage / Dosage

The sweet orange is the most widely cultivated member of the citrus genus. Today, there is no wild form, and it is considered a hybrid between mandarin and pomelo. It is among the world’s most commonly grown fruit trees.

Orange wood is hard, easily worked and turned, and has a yellowish color. It is used for furniture and woodworking, though it is susceptible to termite damage, and the dust may cause asthma.

The oil pressed from seeds is used as a table oil; about one kilogram of flowers yields one gram of oil highly valued in cosmetics. The plant is an important honey plant, and about a quarter of all honey from the western USA coast is citrus-based.

Orange flowers are valued for their fragrance and are included in teas and herbal blends. In folk medicine, orange petal infusions are used to calm the nerves, lower high blood pressure, relieve vomiting, asthma, fevers, and lack of appetite.

The fruits are an excellent source of vitamin C, eaten fresh, canned, or juiced. Orange peels yield pectin and essential oils used to flavor foods, cosmetics, and in tinctures for pharmacy and medicinal purposes.

Sweet orange essential oil (Citrus oil, Aurantii etheroleum) is derived from the rind, comprising up to 2.5% of the rind and rich in linalool and methylanthranilate. Other compounds include limonoids (bitter compounds), flavonoids, and furocoumarins.

The oil has been officially recognized in numerous pharmacopeias as a gentle antispasmodic remedy. In folk medicine, both the oil and flowers are used to relieve sore throat, nervousness, insomnia, promote relaxation, relieve tension and anxiety, and aid appetite and digestion. English herbalists recommend the oil for pain relief during inflammation, treatment of acne, and as a component in household cleaners due to its fresh and penetrating aroma.

In cosmetics, sweet orange essential oil is used in creams for oily and mature skin, oral hygiene preparations, massage lotions, and anti-cellulite ointments. Some manufacturers also use it in deodorants and aromatherapy diffusers.

Antimicrobial Effects

Research from 2012 demonstrated that at concentrations of 1% and lower, sweet orange oil could significantly inhibit the growth of Escherichia coli from beef under refrigeration, supporting its use as a natural antimicrobial and preservative. Other studies found it can destroy antibiotic-resistant Staphylococcus aureus strains infecting human skin cells, and—with high d-limonene content—can inhibit molds like Aspergillus niger, Mucor wutungkiao, Penicillium funiculosum, and Rhizopus oryzae, thus improving food quality.

Anxiety and Depression

Aromatherapy with sweet orange oil can ease symptoms of anxiety and depression. A 2013 pediatric study showed it reduced cortisol levels and heart rate in children experiencing anxiety during dental procedures. A 2015 study found inhalation lowered anxiety in women during childbirth compared to a placebo. Another study (2019) noted an antidepressive effect of limonene, a major component of the oil.

Pain Relief

Clinical studies since 2008 suggest orange oil may relieve pain. One trial using orange and ginger oil blends topically for knee pain found significant short-term relief. Another 2017 study found that inhalation of orange oil reduced pain in patients with fractures compared to control groups.

Other Effects

Limonene exhibits anticancer potential, inhibiting cell growth and promoting cell death in colon cancer cells. Orange oil has also shown inhibitory effects on prostate and lung cancer cells and has demonstrated antioxidant properties. Other studies found that inhalation of the oil improved athletic performance and lung function, supported weight loss, and lowered cholesterol.

Sweet orange oil also acts as an insecticide and natural preservative.

Precautions

The most documented side effect of sweet orange and its products is increased sensitivity leading to allergic reactions. The oil may cause photosensitivity, resulting in skin inflammation, blistering, and darkening after UV exposure. Avoid sun exposure following topical application. Keep essential oil away from children and eyes; if eye contact occurs, rinse thoroughly.

Active Constituents

Sweet orange fruits are low in fat, fiber, and protein, with trace amounts of fatty acids and almost zero cholesterol. They are a substantial source of sugars, sodium, potassium, calcium, magnesium, phosphorus, zinc, vitamin C, carotene, small amounts of vitamin E, B6, thiamine, riboflavin, niacin, nitrogen, iron, copper, and zinc. Essential oil makes up to 2.5% of the rind, primarily linalool, limonene, and methylanthranilate, with other components including limonoids, flavonoids, and furocoumarins.

Traditional Dosage

Dried peel can be taken in doses of 4–6 grams per day as part of herbal tea blends. Tincture: 2–3 ml daily. Liquid extract: 1–2 ml daily.

For aromatherapy, add 3–5 drops of oil to water in a diffuser, or place a container with oil on a heat source. In a sauna, several drops can be applied to hot stones. For baths, add up to 20 drops of oil to warm water (about 30°C) and soak for up to 30 minutes. For inhalation, use 5–10 drops in hot water and inhale for 5–10 minutes, up to 3 times a day.