With their fragrant blossoms and deep emerald foliage, gardenias are a staple of the Southern garden. Traditionally limited to gardens of the Deep South, newer varieties such as Jubilation™ and ScentAmazing™ Gardenia are hardy to USDA Zone 7, allowing a wider range of gardeners to enjoy this exquisite evergreen shrub. The following tips will help you get the most from your plants, whether you are in the heart of gardenia country or growing on the fringe.
Location, Location, Location
It’s always easier to avoid plant problems than to fix them, and location is the key to success. Gardenias perform best when they receive intense morning light and shade from the hot afternoon sun. Sun exposure is necessary for proper flower bud development – with too little sun plants will produce leggy growth and few flowers. On the other hand, too much sun can cause blooms to fade quickly.
Also consider soils when selecting a planting site. Gardenias require an organically-rich acidic (pH 5.0-6.5) soil with good drainage. Give plants plenty of room to stretch their roots – gardenias do not tolerate crowding and root competition. Finally, select a location with good air circulation to limit pest problems.
Winter weather is another consideration when placing gardenias, especially for more northern gardeners. Gardenias can suffer cold damage at 15 degrees Fairenheit. Select a site protected from extreme temperature fluctuations and strong winds in winter, such as the east or northeast side of a house. Be prepared to cover plants when temperatures drop to 15 degrees or lower. Use a porous material such as a sheet, blanket or cardboard box, and keep plants covered until temperatures rise. Heavy winter mulch applied after the first killing frost in autumn will protect the shallow roots over winter.
It takes a lot of resources to produce all of those magnificent blossoms. Apply an acidic fertilizer according to soil tests when new growth begins in spring and again mid-summer. An azalea or camellia fertilizer will work well, or choose blood meal, fish emulsion or bone meal. Soil pH impacts the availability of nutrients to gardenias. Gardenias require low soil pH between 5.0 and 6.5. When pH is too high, some nutrients, such as iron, may become limited. Soil tests are the best way to determine both soil pH and the specific nutrient needs for your garden.
Water is also essential for flower development. A plant will drop its flower buds before opening if water stress is an issue. To avoid this problem, maintain an evenly moist soil, but avoid overwatering, as gardenias do not like wet feet. Mulch plants to help maintain even soil moisture.
Mulch is also important for weed management around plants because shallow-rooted gardenias do not tolerate cultivation.
Gardenias produce the buds for spring blossoms in late summer and fall of the previous year. To avoid removing these flower buds, wait to prune until early summer after the first big flush of flowers. If plants are well suited to their location, very little pruning will be needed. Cut back uneven branches and shape lightly.
The fragrant flowers of gardenia beg to be placed in a location where passersby will enjoy the aroma. Place gardenias near entryways, patios or windows. Consider mixing gardenias among other scented blooms such as lavender and sage. Gardenias look right at home with tropical plants including Blue Fountain™ Agapanthus and Little Black Magic™ Dwarf Elephant Ear. Gardenias also perform well in large containers, but will need to be moved to a protected location over winter, such as a cool greenhouse or enclosed porch.