Water jasmine

Identification and origin

Wrightia religiosa belongs to the dogbane family, Apocynaceae. It was first described as Echites religiosus, its only synonym. The genus honors William Wright, a Scottish physician and botanist; the epithet religiosa means “sacred” or “related to religious rites.” In Thailand, Buddhist monks often plant it near their temples, and it is a common sight in pagoda and home gardens throughout Southeast Asia.

Its natural range runs from Bangladesh to southern Guangdong in China, through Myanmar, Thailand, Laos, Cambodia, and Vietnam, down to northwestern Peninsular Malaysia. It has been introduced to the Philippines. It grows in evergreen forests, but it has been cultivated for so long that its original distribution is now hard to pin down.

It is an evergreen shrub with slender branches, often with an almost flat top. In cultivation it commonly reaches up to 6.5 ft, sometimes 10 ft, and can become a small tree of 16.5 ft at most. It grows fast.

The leaves are opposite, thin, smooth, light green, oval to elliptic, with a smooth edge and a pointed tip. They have almost no leaf stalk and measure 0–3 in long by 0–1 in wide. The cultivar ‘Fine Leaf’ has finer foliage, and there is also a variegated form.

The white, intensely fragrant flowers have five obovate petals arranged in a star, each 0–0 in long. The dark-tipped stamens are fused into a small central column. Borne in small clusters where the leaves meet the stem, the flowers dangle from very thin stalks 0–1 in long. They appear again and again through the year. Double-flowered forms are also grown. After pollination, pairs of narrow pods 3–7 in long develop, looking rather like beans; their elongated seeds carry a tuft of hairs and are spread by the wind. A plant raised from seed can bloom from its second year.

Light

In the wild it grows in full sun or partial shade. In a pot it loves heat and direct sun: outdoors, give it the sunniest spot you have during the warm season.

When it comes indoors, set it right against the brightest window in the house. In winter, natural light often falls short, and a grow light can then become necessary.

Watering

It uses a lot of water while it is growing, yet it cannot stand soggy soil. Don’t water on a fixed schedule: feel the surface of the potting mix and water thoroughly as soon as it starts to dry, until water runs out of the drainage holes, then empty the saucer.

The root ball should never dry out completely, but too much water is just as harmful. Needs change with light, heat, pot size, and how vigorously the plant is growing: a plant in full sun and full growth drinks far more than a resting one.

Potting mix

It needs soil that stays moist but drains perfectly. In a pot, choose a coarse, airy mix that lets water run quickly through the root ball.

This matters: the roots are very vigorous and soon fill the pot. A root ball packed so tight that water can no longer soak in quickly weakens the plant.

Temperature

This is a tropical plant that loves heat and should be kept above 64 °F. Below that, it becomes semi-deciduous: it sheds part of its leaves and its growth slows. It cannot tolerate frost. Grown as an indoor bonsai through the cold season, like other tropical species, it appreciates daytime temperatures of 68–77 °F.

Planted in the ground, it can only be grown in very mild climates, in USDA zones 10 and 11. Elsewhere, move it outside once the nights are warm and bring it in as soon as temperatures drop in fall, placing it by a very bright window.

Repotting

Check the roots every year and repot at least every two years, at the time of the warmest nights. The roots grow strongly and tolerate substantial pruning at repotting time. Removing part of the foliage at the same time reduces stress on the plant.

During the growing season it is a heavy feeder that appreciates a high-nitrogen fertilizer. Apply a solid organic fertilizer every four weeks or a liquid fertilizer every week, then only once a month in winter, when it grows less.

Pruning

It takes pruning very well, even hard pruning, and readily sprouts again from old wood; in tropical countries it is used for clipped hedges. Prune large branches in spring, before strong new growth begins.

For dense branching, let a young shoot develop several pairs of leaves, then cut it back to a single pair. Flowers often appear after the third pair of leaves.

It is also a popular bonsai species. Young branches can be wired, but growth is so fast that the wire must come off in time, before it cuts into the bark.

Propagation

It can be propagated from seed, from stem or root cuttings, and by air layering. Seeds form in the pods that sometimes follow flowering.

Common problems

A single symptom can have several causes: check the moisture of the potting mix, the light, and the temperature before you act.

• Yellow leaves: often overwatering, but also a lack of fertilizer.
• Leaf drop: in winter, usually a temperature below 64 °F.
• A plant that weakens: a root ball crammed with roots, which water no longer penetrates, is a frequent cause.
• Pests: scale, mealybugs, and aphids sometimes settle in. Treat with a suitable product if needed, while also improving growing conditions.

Toxicity

No toxicity has been reported: water jasmine does not appear among the plants listed as toxic to dogs and cats, and no toxicity to people or animals is known. Its bark and roots are, however, used as a traditional remedy in some countries, so keep children and pets from chewing on any part of the plant.