The intense, heady odor of creamy gardenia blossoms is the main reason to grow gardenias (Gardenia jasminoides, sometimes known by the former name G. augusta) in gardens or containers. Their blooming period is primarily in spring, but some varieties bloom during the growing season. The bushes have evergreen, dark-green leaves and range in height in only 1 or 2 feet tall to 8 or more feet tall. The flowers are mostly double and utilized for corsages and in leis.
Gardenias prefer moist, well-drained, acidic soil rich in organic matter. Apply fertilizer in spring and early summer to get the best flower production and optimum plant growth, reaching a particular cultivar’s full height. If soil is not acidic enough, gardenia leaves turn yellow. Lower soil pH with an acid-formula plant food. Gardenias are frost-tender, growing in U.S. Department of Agriculture plant hardiness zones 8 through 11, but several varieties are more cold-hardy. In areas where nematodes are a issue, gardenia is grafted onto rootstock of starry gardenia (G. thunbergia), which is nematode-resistant. Several cultivars are available.
Gardenia varieties that grow to 6 or more feet tall are useful as background shrubs or foundation plantings. “First Love,” also called “Aimee Yoshioka,” (G. jasminoides “First Love”) is also an early-blooming variety with flowers up to five inches broad, and the plant grows 6 to 12 feet tall and 6 feet wide. “August Beauty” (G. jasminoides “August Beauty”) ranges from 4 to 6 feet high and 3 to 4 feet broad; it flowers heavily. “Mystery” (G. jasminoides “Mystery”), the cultivar most used for corsage flowers, is a fast-grower to 4 to 12 feet tall, as is “Mary Ann” (G. jasminoides “Mary Ann”). “Coral Gables” (G. jasminoides “Coral Gables”), flowering in mid-season, and “Miami Supreme” (G. jasminoides “Miami Supreme”) with early flowers, both can achieve a height of 15 feet.
Cultivars that typically grow to about 4 feet tall produce tidy specimen plants or boundary plantings. “Veitchii” (G. jasminoides “Veitchii”) grows to 4 feet tall and is a prolific bloomer with 2-inch blossoms; sometimes it’s known as ever-blooming gardenia. “Veitchii Improved” (G. jasminoides “Veitchii Improved”) reaches 5 feet tall and contains blossoms to 3 inches broad. “Chuck Hayes” (G. jasminoides “Chuck Hayes”) grows to 4 feet tall and broad, bearing 3-inch blossoms in spring and again in fall. It’s heat-tolerant and cold-resistant. “Golden Magic” (G. jasminoides “Golden Magic”) is unusual in flower color; its own white flowers age to a golden yellow. This sport of “Mystery” arose in Hawaii and grows to 3 feet tall.
Some gardenias are extremely low-growing, maintaining heights of 1 to 2 feet tall or lower. They do well as ground covers, edgings or potted plants. “Radicans,” (G. jasminoides “Radicans”) sometimes called “Prostrata,” is a mini that’s 6 to 12 inches tall and 2 to 3 feet wide. Its leaves and flowers are also modest in scale, at 1 inch long and one inch broad, respectively. A variegated selection, “Radicans Variegata,” (G. jasminoides “Radicans Variegata”) includes white leaf margins. Sometimes normally colored branches occur, and they need to be pruned away. “Kimura Shikazaki” (G. jasminoides “Kimura Shikazaki”) also called “Four Seasons,” flowers spring through fall on the 2- to 3-foot high bush.
Single-flowered gardenias vary greatly in adult height and width, and they have a tendency to be more cold-hardy compared to double-flowered varieties. Their easier flowers have an appeal all their own. “Shooting Star” (G. jasminoides “Shooting Star”) includes upright growth, reaches 8 feet tall, has large leaves and single blossoms blooming in spring and early summer. It’s hardy to 0 degrees Fahrenheit and therefore can grow in U.S. Department of Agriculture zone 7. “Klein’s Hardy” (G. jasminoides “Klein’s Hardy) includes intensely fragrant, 3-inch ivory blossoms and reaches 3 to 4 feet high. In addition, it can survive 0 degrees Fahrenheit. It requires summer heat for good blossom, however. “Grif’s Select” (G. jasminoides “Grif’s Select”) is hardy to approximately 5 degrees Fahrenheit, bearing blossoms in spring and early summer and reaching 3 to 4 feet in height. “Daisy” (G. jasminoides “Daisy”) includes white, flat-faced blossoms and grows to 6 feet tall. “Kuchinashi” (G. jasminoides “Kuchinashi”) grows even lower, to only 2 to 3 feet tall, and contains ample, open, white flowers. “White Gem” (G. jasminoides “White Gem”) is the smallest, growing 1 to 2 feet high, and produces ivory, star-shaped flowers spring through the summer. This dense, compact cultivar does well as a potted plant or foreground border plant.