Gardenia hydrophila (Mok Luang) is an evergreen, large shrub native to tropical Thailand, that grows 5-10 feet tall. The beautiful, fragrant white or off-white flowers make Gardenia hydrophila an attractive garden plant, and it also attracts butterflies and hummingbirds. This plant needs full sun to partial shade, and regular watering. It is best grown in USDA Zones 9-11.
The flowers are sweetly but delicately scented. They are produced in a cluster, with the central flower opening first, and the others following in successive whorls. The flowers are about two inches long and one and a half inches across. The plant flowers at the end of new growth, so needs to be pruned after flowering.
In Thai language this plant goes by the same name as Wrightia religiosa , with the addition of "big" or "important" (Mok Luang) but it's not related to Wrightia.
Gardenia hydrophila can be grown in pots in cold regions, as long as they are brought in during winter months to protect them from the frost. For outdoor growing in colder climates, the plant should be in a sheltered position facing south or east, and covered with a thick layer of mulch or wool to keep warmth and retain moisture in the soil. For container growing, it is advised to use a potting mix that drains well. It is best to water the plant regularly, as it prefers moist soil, but allow the topsoil to dry out in between. It is also important to provide plenty of sun and to prune it regularly, to help encourage blooming and keep it from becoming woody.