Gardenia

( gar - DEEN - ee - uh )

At-A-Glance Information

This genus of evergreen shrubs includes species that prefer full sun to partial shade and need regular to ample water. They are valued for their strong fragrance and beautiful shiny dark leaves. Gardenia shrubs are native to the tropical and subtropical areas of Africa, Asia, Madagascar, Australia and the Pacific Islands. They produce white (rarely yellow) flowers. Gardenia shrubs can be used as potted plants on patios or walkways or be installed in the ground in mixed beds and borders. Take care when planting Gardenia in the landscape; although these plants are non-toxic to humans, they are toxic to animals, causing stomach problems.

Gardenia Species and Varietals

The genus Gardenia is included in the Coffee family, Rubiaceae, and includes 128 species and over 200 varieties. The genus was named by Carl Linnaeus and John Ellis for Alexander Garden, a Scottish-American naturalist. Gardenia growing zones vary by species; see the descriptions below for more information. To find your zone, click here: Zone Map.

Gardenia brighamii (Nānū, Naʻu, Forest Gardenia)
This critically endangered species forms a small tree that reaches up to 16 feet tall when mature. Leaves are glossy and dark green, to over 4 inches in length. Flowers are white and powerfully fragrant, and are followed by round fruits. This species of Gardenia grows well in USDA hardiness zones 8-10. It can handle very short periods of slightly freezing temperatures, but otherwise prefers a range of between 70 and 80 degrees Fahrenheit.

Gardenia jasminoides (Gardenia augusta) (Gardenia, Cape Jasmine, Cape Jessamine, Common Gardenia, Danh-Danh, Jasmin)
Grows best in USDA hardiness zones 8-10 or Sunset growing zones 7-9, 12-16, 18-24, H1 and H2. This species is native to tropical and subtropical regions of China, Japan, and Taiwan. Bright green leaves and very fragrant double-white flowers make these shrubs great garden ornamentals. They are hardy to 20 degrees Fahrenheit and need summer heat to thrive and bloom well. These shrubs are somewhat difficult to grow in clay or alkaline soils. Great for containers and raised beds, and can also be used as hedges or screens. Varieties are outlined below:

'Aimee' ('First Love')
Upright growth 4-6 feet tall and wide. Very large double blossoms with elegant spirals. Blooms spring to summer.

'August Beauty'
Erect growth to 4-6 feet tall and 3-4 feet wide. Loosely double flowers show in early summer.

'Belmont'
Vintage variety that grows to 5 feet tall and wide, with large leaves and rose-like blossoms; blooms late spring to early summer.

'Chuck Hayes'
Hardy variety that is heat tolerant. 4 feet tall and wide. Double flowers bloom in summer, heavy fall rebloom.

'Frostproof'
To 5 feet tall and 4 feet wide. Profuse blooms spring through summer. Buds are undamaged by late frosts.

'Kimura Sikazaki'
('Four Seasons')
Compact grower to 2-3 feet tall and wide. Long bloom season spring to fall.

'Kleim's Hardy'
Forms a 2-3 foot high mound. Star shaped bloom profusely in early summer. Cold hardy.

'Miami Supreme'
6 feet tall and wide, with large double flowers that bloom in spring. Periodic blooms in summer.

'Mystery'
6-8 feet tall and wide. Formal blossoms show in midsummer to fall. Needs pruning to keep it neat.

'Radicans' ('Prostrata')
Dwarf to 6-12 inches tall and 2-3 feet wide. Double flowers bloom in early summer. Can be used as groundcover or container plant.

'Summer Snow'
To 4-5 feet tall and wide, with fragrant double blooms that pop up late spring through summer. Very cold hardy.

'Veitchii'
(Everblooming Gardenia)
To 4 feet tall and 6 feet wide. Pure white blossoms late spring to fall, and continues into warm winters.

'White Gem'
Compact dwarf variety gets 2 feet tall and wide. Single flowers bloom continuously spring through summer. Great for containers.

Gardenia taitensis (Tahitian Gardenia, Tiaré Flower)
This species of evergreen shrub reaches up to 10 feet tall and produces glossy, dark green foliage. Leaves are large, reaching to 6 inches in length. Tahitian Gardenia grows well in USDA hardiness zones 10 and 11. This species is the national flower of French Polynesia and the Cook Islands. Despite its common name, it is neither native nor naturalized in Tahiti. It is used to make Monoï Oil.

Gardenia thunbergia (Forest Gardenia, Mutarara, Tree Gardenia, White Gardenia, Wild Gardenia, Buffelsbol, Buffalo Ball, Stompdoring, Blunt Thorn, Wildekatjiepiering, Wild Gardenia)
This species grows well in USDA hardiness zones 9b-12 or Sunset growing zones 16, 17, 21-24, H1 and H2 and is native to South Africa. It blooms in winter in its native range and reaches 6-12 feet tall and 5-10 feet wide. Flowers bloom more profusely with age, fruits appear after blooms and remain for years afterwards.

Caring for Gardenia

Take care when planting Gardenia in the landscape; although these plants are non-toxic to humans, they are toxic to animals, causing stomach problems. Grow Gardenia shrubs in full sun to light shade, providing afternoon shade in warm climates. Ideally, they should be getting between 4 and 6 hours of morning sun. They prefer moist, well-draining soil that is rich (amended with plenty of organic material) and has a pH of between 5.0 and 6.5 (acidic). Soil pH is important for these plants; their foliage will yellow and growth will be poor in soil that is too alkaline. If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Gardenias are sensitive to extremes in temperature, preferring daytime temperatures of between 65 to 70 degrees Fahrenheit and nighttime temperatures of between 60 and 65 degrees Fahrenheit. Cover shrubs when temperatures will drop below 30 degrees Fahrenheit. They prefer high humidity, and do well in protected areas of the garden.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These shrubs should be pruned for shape when the plant is dormant in late winter or early spring to promote a bushier habit. It is not recommended to shear Gardenia shrubs; selective pruning is best. Flowers typically last for between one and three days; deadhead spent blooms to clean up the look of the shrub and encourage more flowers to form. Gardenia shrubs can survive in the landscape for decades (between 30 and 50 years) before needing to be replaced. Proper care and the right climate will result in a longer-lived shrub.

Caring for Gardenia in Containers
Gardenia shrubs are commonly grown in containers, a situation which allows for gardeners in cooler climates to grow these tropicals outdoors during the warmer months of the year. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away. Fill with a well-draining potting mix amended with organic material and perlite, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water regularly as the plant establishes itself in its new home. Once established, waterings can be lessened, but plants still appreciate consistent moisture. Gardenia plants grown in containers will need more frequent irrigation than those grown in the ground. As a general rule of thumb, water whenever the top inch or two of soil feels dry to the touch.

Gardenias are heavy feeders; a slow-release Fertilize every 2-4 weeks during their active growing and blooming seasons (March through October) with a diluted fertilizer that is good for acid-loving plants. Hold off on fertilizing from November through February. Prune to remove dead, damaged, or diseased foliage at any time during the growing season. Flowers typically last for between one and three days; deadhead spent blooms to clean up the look of the shrub and encourage more flowers to form. Every few years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that it needs to be potted up; choose a slightly larger container and repot.

Harvesting Gardenia
Gardenia flowers are fragrant, and can be used in cut flower arrangements and are popular additions to boutonnières or corsages. They are in bloom from late spring into summer. As cut flowers, Gardenias provide elegant foliage and white flowers as well as intense fragrance to arrangements. They combine well with many different types of flowers. The best time to harvest is in the early morning or late evening when temperatures are at their coolest. Cut flowering branches (at least 3-4 inches long) using sharp, clean shears or snips, remove the lower leaves from the stem, and drop them in a bucket of cool water. They have a short vase life, lasting for just 1-3 days before fading. Foliage can remain behind to provide greenery.

Propagation

Gardenia can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your shrubs, follow the instructions below:

Propagating Gardenia by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 3 to 4 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Gardenia by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant, and that your Gardenia grown from seed will take around 2-3 years to start producing blooms. To propagate by seed, you will need a razorblade, a fine mesh strainer, a paper towel, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. You'll know the seed pods are ready to be harvested when they are about 1.5 inches in diameter and have turned a dark brown color. Remove the pods from the plant, and cut them open with a razorblade. Pick out the seeds from the pod with your finger. Rinse the seeds using a fine mesh strainer and lay them out on a paper towel to dry. Then, place the seeds in a paper bag and allow them to dry out in a cool, dark, dry place for about 20 days to a month.
In early winter, water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 4-6 weeks from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.