Sweet olive

Identification and origin

Osmanthus fragrans belongs to the olive family, Oleaceae, alongside olive and privet. Its native range runs from the Himalayas to southern Japan, through China, Taiwan, and Indochina. The genus name comes from the Greek osme, fragrance, and anthos, flower; fragrans means “fragrant.” The Chinese city of Guilin takes its name from the plant.

It is a dense, upright evergreen shrub, often multi-stemmed, with a medium to slow growth rate and a long life. In gardens it reaches 10–19.5 ft tall and 10–14 ft wide, though it often stays around 6 ft in landscapes. As it ages, the foliage gathers toward the branch tips.

The opposite, leathery leaves are 2–4 in long: glossy dark green above, paler below, with smooth or finely toothed edges, and both kinds often appear on the same plant.

The flowers, about 0 in across, are white, waxy, and four-lobed, clustered in the leaf axils. Inconspicuous as they are, they give off a powerful apricot fragrance. The main bloom comes in fall, often followed by a second flush in late winter or spring and a few scattered flowers in summer. The fruits are small blue-black drupes.

The variety aurantiacus bears pale orange flowers, less abundantly. Cultivars include ‘Apricot Gold,’ ‘Butter Yellow,’ ‘Fudingzhu,’ and ‘Thunbergii.’ In China, growers recognize white, yellow, and orange groups that bloom once in fall, plus a group that reblooms from fall to spring. The flowers scent tea, and their extract goes into luxury perfumes.

Light

It grows in full sun or partial shade, with at least two hours of direct sun a day. The ideal is morning sun with afternoon shade, or light, shifting shade. Where summers are hot, that afternoon shade is essential. In cooler regions, on the other hand, give it full sun against a south- or west-facing wall, sheltered from cold winds.

In a container over winter, give it as much light as possible while shielding it from scorching sun behind glass. Plant it near a door, a walkway, or a patio so you can enjoy the fragrance.

Watering

It likes moist soil that dries slightly between waterings. After planting, water whenever the top couple of inches of soil are dry while the roots settle in. Once well established in the ground it tolerates drought, but it grows and blooms better with extra water during hot, dry spells.

In a container, during active growth, water thoroughly when the surface of the mix is dry and let the excess drain away. In winter, water sparingly, just enough to keep the root ball from drying out completely. Go by feel rather than by the calendar: the roots cannot stand to sit soggy.

Potting mix

In the ground it adapts to clay, chalky, loamy, or sandy soils as long as they are fertile and drain well; it prefers slightly acidic, moist soil and only struggles in poor sand.

In a container, use a peat-free, soil-based potting mix in a heavy pot with drainage holes. During the growing season, feed with a balanced liquid fertilizer about once a month, then stop in fall and winter.

Temperature

It is hardy only in mild regions: it withstands frosts of about 23 °F in a sheltered spot and is grown in the ground in USDA zones 8a to 11b. A freeze that hits the young shoots reduces the following fall’s bloom.

Where winters are harsher, grow it in a large container that moves under cover before hard freezes, into a cool greenhouse, a sunroom, or a bright, cool room, and goes back outside when the weather warms. In the garden, a sunny wall sheltered from the wind gives the best protection.

Repotting

In a container, repot in spring, before growth resumes, when the roots line the sides of the pot. Choose a container with drainage holes that is only slightly larger, use the same soil-based mix, and keep the plant at the same depth. In other years, simply replace the top layer with fresh mix.

In the ground, plant no deeper than it sat in the pot and water regularly through the first season.

Pruning

It needs little pruning and does very well left to grow naturally. It does take pruning well, though, and can be trained as a hedge, a small multi-trunked tree, or an espalier.

Prune lightly from mid- to late spring, once frost has passed, starting with dead or badly placed wood. Fall flowers form on the current year’s growth, so heavy or late pruning reduces the bloom. Moderate pruning is enough to keep the plant in bounds and encourage branching.

Propagation

Cuttings are the most common method, since the species roots fairly easily.

• Softwood cuttings, from late spring to early summer: flexible stems 4–6 in long, one or two leaves left at the top, two or three nodes, base dipped in rooting hormone. They root quickly but need very steady warmth and humidity.
• Semi-hardwood cuttings, in late summer or early fall: 2–2 in pieces of wood that is starting to turn brown, with the top two leaves trimmed, under mist or in a closed case with bottom heat. They root more slowly but succeed more often.
• Hardwood cuttings, from late fall to early winter: slow to root.
• Air layering, from late spring to early summer: remove a 0–1 in ring of bark 12–20 in from the tip of a branch, wrap it in moist sphagnum moss, then in plastic. Roots form within a few months.

Seed is unreliable: soak the seeds in warm water for a day and sow them in warm, humid conditions. Seedlings vary and take years to bloom.

Common problems

• Aphids on new shoots.
• Scale insects on stems and leaf undersides, especially on stressed plants.
• Honey fungus in the ground: gradual decline with no obvious cause.
• Few or no flowers: frost on young shoots, heavy or badly timed pruning, too much shade, or a plant that is too young.
• Scorched foliage: severe cold, drying wind, or harsh afternoon sun in hot climates.

The same symptom can have several causes: check exposure, soil moisture, recent temperatures, and the condition of the roots before acting.

Toxicity

No toxicity has been reported for sweet olive, either for dogs and cats or for people. Its flowers are even edible: in East Asia they scent tea and go into jams, cakes, dumplings, and soups. If a pet or a child has chewed a large amount of foliage and shows unusual symptoms, contact a veterinarian or a poison control center as a precaution.