Gardenias are among the most popular of ornamental shrubs for landscapes and gardens. These evergreen shrubs have oval, medium- to dark-green leaves and large, waxy flowers ranging from pure white to pale ivory. They are very fragrant, with a scent reminiscent of a combination of jasmine, nutmeg and vanilla.
Gardenias originated in China and have been cultivated there for more than 1,000 years. Imported to Europe and eventually to the United States, the majority of gardenias grown today are cultivars of Gardenia augusta.
Gardenias can be grown in a range of soil conditions, growing best in fertile, well-drained, acidic soils with a pH between 5.0 and 6.5. They are semi-tropical, preferring mild and humid conditions in USDA hardiness zones 9 or 10, although they can be grown as far north as zone 7. For the best flowering conditions, gardenias should be raised in full sun or little shade. It is also important to provide enough space, as some cultivars can grow to over 12 feet tall.
Gardenias belong to the Rubiaceae family in the genus Gardenia, which has more than 200 species. In the United States, two species are generally grown. Gardenia thunbergia is primarily grown as root stock. Gardenia augusta has many cultivars in a range of flower styles, sizes and colors, duration of bloom and growth characteristics.
Miami Supreme is a fast-growing cultivar that can grow to a height of 15 feet. The foliage is medium to dark green. The flowers are white, 3 to 5 inches across. They bloom twice, early in the growing season.
Aimee Yoshioka is a fast-growing cultivar that can reach a height of 12 feet. The foliage is brilliant dark green. The flowers are double, ivory white, 3 to 5 inches across. They bloom twice in the middle of the growing season.
Glazerii grows at a medium rate to a height of 12 feet. The foliage is medium green. The flowers are double, white, 3 to 4 inches across. They bloom twice, early in the season.
Radicans is slow growing reaching a height of 2 to 3 feet. The foliage is small and lustrous. The flowers are single, white and small, about 1 inch across. They bloom late in the growing season.
The Veitchii cultivar has lush green foliage and grows to 12 feet high. The flowers are delicate and white, 2 to 3 inches across. This cultivar blooms early and can bloom as many as four times in a season. They grow slowly.
Variegata grows to 4 to 6 feet and has a rounded form. It is a slow grower. Variegata has single, creamy white, fragrant flowers, 2 to 3 inches across. The leaves are variegated, hence the name.
Klein's Hardy has a rounded form, growing to 4 feet. The flowers are single, ivory and very fragrant. The foliage is lustrous green. It also has good cold hardiness.
Chuck Hayes grows to 6 feet. The flowers are semi-double, ivory-white, blooming in early summer. It may bloom sporadically through fall, and it demonstrates good cold hardiness.
A wide range of Gardenia cultivars are available commercially in United States. These vary significantly in flower, foliage and form. Consult with your local nursery or extension office to determine what cultivar is right for your specific landscaping needs.