How to Plant, Grow and Care For Gardenias

Gardenias are known far and wide for their intoxicating scent as well as their beautiful white flowers. They are a fairly common garden flower due to their low-maintenance nature and adaptability. They can grow quite well both indoors and outdoors. Gardenias are close relatives to the coffee plant, which shares similar, glossy, green foliage and aromatic blossoms.

The creamy white flowers with their dreamy redolence are a prized perennial shrub in many a classic Southern Garden. After the last great freeze in my area, they were one of the very few beloved plants left unscathed in my personal garden, and so, suffice it to say, I am a Gardenia believer.

There are more than 200 varieties of gardenia, each one lovelier than the last. If you’ve decided to add this hardy shrub to your garden this season, you’ve made an excellent choice. Continue on to find out all you need to about successfully growing gardenias both indoors and outdoors this season.

Classification

Gardenias are perennial evergreen shrubs. They hold their glossy foliage year-round. They are quite cold-tolerant and will bloom year after year if properly cared for.

Their evergreen nature makes them an attractive shrub all year. Gardenias are mainly classified by size and flower formation. The two most popular species are G. jasminoides and G. taitensis.

G. jasminoides

Gardenia jasmoinoides is the most common species of gardenia. Also known as Cape Jasmine, it is a large shrub with highly fragrant flowers which can bloom year-round in warmer climates, and in spring and summer in cooler climates.

This winner of the Royal Horticultural Society’s Award of Garden Merit is a versatile plant. It can grow in full sun to light shade, make a wonderful privacy hedge, and their double-petaled blooms make wonderful cut flowers.

G. taitensis

The Tahitian gardenia, or tiare flower, is a large, tropical, evergreen shrub. It is native to the South Pacific despite being named otherwise. It is from the small, pinwheel-shaped flowers of the Tahitian Gardenia that monoi oil is derived.

These pretty blooms are also, commonly made into flower necklaces called “Ei” in the Cook Islands, and “Lei” in Hawaii.

Leaf Formation

The leaf formations of most gardenia plants are a whorl of shiny, dark green, ovate leaves. The color and size can vary by species and variety.

Gardenias are always evergreen and retain their pretty foliage even in quite cold temperatures. Even in a hard freeze, it is common for gardenias to retain their foliage unscathed.

Flowers

Gardenias are best known for their wonderfully fragrant flowers. Their blooms are white, although, in soil that is too alkaline, there is a chance they may turn yellow.

All Gardenias have fragrant flowers. Their creamy, waxy, white blooms come in single and double-petal forms and rose forms. They range in size from only a few centimeters wide, to 5”-6” inches in diameter.

Propagation

Gardenias are not difficult to propagate, however, like most plants, when grown from seed, it takes several years for them to flower. Gardenias propagated from cuttings will flower much sooner, so this is generally the preferred method.

From Cuttings

Propagating Gardenias from cuttings is a simple process and one that can work in tandem with pruning. A cutting should be at least 5” long and should include the tip of the branch. This works best if the cuttings are taken from green wood (new growth) as these will root quickly.

Prepare a pot with moist peat or potting soil. Dip the cut end of the gardenia in rooting hormone, and then simply stick your finger in the soil to make a hole and place the end of the cutting in the hole.

Set your potted cutting in bright, but indirect light, keeping the soil moist. Your cutting will take about 4-6 weeks to develop roots. Try to keep your cutting in a humid space during the rooting process, this will ensure that the foliage remains healthy until the roots are stable enough to support it.

From Seeds

Gardenias propagated by seed are a little bit unpredictable. The germination time of gardenia seeds can vary widely, from a few weeks to a few months. Germinating seeds is typically the most successful when fresh seeds are sown. Seeds should be soaked overnight, before sowing.

Seeds should be sown about ¼ of an inch deep. Soil that drains well but holds some moisture should be used, perlite or a mixture of peat moss and sand both work well. Try to keep the soil moist and keep the temperature steady at around 75°F.

Grafting

Gardenias can also be propagated by grafting. This is typically done to produce plants with higher pest resistance and involves grafting the desired variety onto rootstock that comes from a resistant cultivar.

How to Grow Gardenias

Gardenias fall into the category of being moderate in maintenance. While they have some specific needs, and will not thrive in opposing conditions, if they are planted properly, they are drought and cold-resistant, and most will bloom with or without fertilizer.

However, there are ways to maximize your gardenia’s flowering potential, which is what we all look forward to when planting one of these lovely shrubs.

Planting Depth and Potting

Gardenias don’t make very good houseplants, however, they do quite well as outdoor container plants. Choose a container that gives your gardenia room to grow, as they don’t love being transplanted. Your container should also have a drainage hole, as gardenias do not tolerate soggy roots.

If you live north of zone 7, planting your gardenia in a pot is a must, as it will need to come in when temperatures drop below freezing for long periods. South of zone 7, your gardenias should be perfectly fine in the ground all year. I live in zone 8 and my gardenias never suffer in the winter.

When planting gardenias in the ground, dig a hole that is twice the width, but only as deep as the root ball. Make sure you are choosing a spot with proper drainage.

Gardenias also thrive in soil that is slightly acidic (5.0-6.5). Adding organic material to sandy soil will help raise the acidity and make these shrubs happier.

Light

Gardenias are versatile when it comes to light needs. Ideally, they do best with several hours of sun, early in the day. In cooler climates, your gardenia will appreciate full sun, but in warm climates, gardenias need some shelter from the mid-day/afternoon sun.

Too little sun will cause gardenias to take on a leggy growth habit, and a scarcity of flowers. Giving a gardenia plenty of sun will cause it to produce more flowers for a longer time period. But be careful. Too much sun will shorten the life of those blooms.

Water

Gardenias have moderate watering needs. Once they are established, they are more drought tolerant, but they don’t do well in completely dry soil. Gardenias need about 2-4 inches of water weekly to perform their best.

This water can come from rain or the hose. Mulching around the base of the plant will help hold in moisture and keep your gardenia healthier in general.

Climate and Temperature

Gardenias thrive in tropical weather. They like humidity and plenty of sun. If you are growing a gardenia south of zone 8, make sure that it gets some respite from the sun during the hotter hours.

Gardenias won’t bloom without a daytime temperature that consistently stays at or above 70°F and around 10° colder at night. They like a humidity level that stays above 60% most of the time.

Most gardenias are cold tolerant to 10°F for a short period. They can survive a hard freeze, but not for a long duration. Gardenias will hold onto their leaves but will not bloom in colder weather. In warm climates, however, it is not impossible for a gardenia to bloom year-round.

Fertilizing

Gardenias benefit from regular fertilizing in spring and summer, but during the fall and winter, fertilizing should be avoided. In spring, give gardenias a fertilizer formulated for acid-loving plants, such as camellias or azaleas.

In addition to nitrogen, phosphorous, and potassium, gardenias also need copper and iron. Keep a lookout for these items in your fertilizer.

As an alternative to commercial fertilizers, gardenias will benefit from a periodic application of coffee grounds and Epsom salt solution. Don’t fertilize more than once per month, as too much fertilizer can be as harmful as none at all. A gardenia that is over-fertilized will wilt and drop flowers early.

Pruning and Maintenance

Gardenias benefit greatly from pruning. Deadheading should be a regular practice with gardenias in bloom. Plucking off spent flowers will encourage the plant to set more buds, as well as save and redirect energy toward new growth. Avoid hard pruning and avoid pruning too late in the year.

Pruning should take place in the summer when the plant is finished blooming. This is typically around July. Trim 2”-3” from the ends of all the branches and avoid cutting back by more than 1/3 at the most.

New green shoots will grow from the cut branches, and they need to strengthen a bit before wintertime. Pruning too late in the year can result in frost damage to the newer growth.

Toxicity

Gardenia plants are toxic to cats, dogs, and horses. If kept indoors, they should be kept out of the reach of children and pets. Ingestion of a gardenia plant causes vomiting and diarrhea, as well as an allergic reaction in some cases.

Popular Varieties

There are a few different popular varieties of gardenias. Let’s take a look at some of the most common varieties you’ll see, as well as where they will survive best, whether that’ s indoors or outdoors.

‘Aimee’

	botanical name G. jasminoides ‘Aimee’
	sun requirements Full to Part Sun
	hardiness zones 8-11

This vareity is known for its extra-large, extra-fragrant blossoms. These rose-form flowers are 4”-5” wide and the perfect shade of cream which compliments its deep green, glossy foliage. This variety blooms from spring through summer.

You will definitely want to plant this shrub in a spot that sees plenty of traffic. The scent is glorious, and the plant is generous with its fragrance.

‘Buttons’

	botanical name G. jasminoides ‘Buttons’
	sun requirements Full to Part Sun
	hardiness zones 8-11

This is a small variety of G. jasminoides with a mounding habit. This shrub prefers to be planted in a slightly shaded spot. Its deep green, glossy leaves are small and ovate and pointed at the ends.

Buttons has small flowers (2” in diameter) that have double petal form and open fully to reveal pretty yellow centers which resemble buttons.

‘Frostproof’

	botanical name G. jasminoides ‘Frostproof’
	sun requirements Full to Part Sun
	hardiness zones 7-11

The name says it all for this cold-tolerant gardenia. I have two of these lovely plants in my yard, and they are every bit as cold-tolerant as my camellias. This is shocking because their leaves are really quite delicate.

‘Frostproof’ is also very heat tolerant, making it an all-around hardy and easily managed variety. The blooms are double-petaled and about 3” in diameter. Frostproof is a slow grower but ultimately reaches up to 5’ tall and 4’ wide.

‘Radicans’

	botanical name G. jasminoides ‘Radicans’
	sun requirements Full to Part Sun
	hardiness zones 8-11

Radicans is a dwarf variety of gardenia with a spreading habit that often reaches 2-3x its height. It makes a really wonderful ground cover with small, double-petaled, fragrant flowers.

It is a big bloomer from late spring through early summer, producing a great deal of aromatic flowers.

‘Tahitian Gardenia’

	botanical name G. taitensis
	sun requirements Full to Part Sun
	hardiness zones 10-11

This one bears mentioning a second time, as it is a unique and beautiful species of gardenia. Growing up to 10’ tall, Tahitian Gardenia is one of the largest varieties.

The flowers are white and shaped like a pinwheel with a warm yellow glow in the center. It is used medicinally, and cosmetically, and beautiful necklaces are made from its fragrant flowers.

Pests and Diseases

Gardenias are met with a handful of challenges when it comes to pests and diseases. They are particularly prone to powdery mildew. As with their finicky nature, the prevalence of pests is simply outweighed by the presence of gardenia’s enchanting flowers.

Whiteflies

Whiteflies are tiny little insects that resemble moths. They are closely related to scale and aphids. When a plant infested with whiteflies is disturbed, the insects will flutter about, making themselves obvious. Whiteflies feed on plant sap and leave behind an excrement called honeydew.

In addition to stunting the growth of the plant, sooty mold can grow on the honeydew, which interrupts the plant’s chlorophyll production.

Whiteflies can be controlled with horticultural oils or insecticidal soap. Make sure to water your gardenia well before applying these agents as they will cause stress on a plant that is suffering from drought.

Japanese Wax Scales

Japanese wax scales are one of several types of scale insects that feed on gardenias. Like whiteflies, they feed on the plant’s sap and leave behind their sticky excrement which forms mold and can attract other insects like ants and wasps.

The worst thing about scales is that they are protected by a waxy coat which is impervious to most treatments. Horticultural oil will dissolve the wax and suffocate scales.

There are also natural predators, such as ladybugs, which can be introduced into the garden to feed on the bad insects.

Aphids

Aphids are another tiny insect that likes to suck the sap out of just about any plant in the garden. An infestation of these guys will likely result in curled and shriveled leaves, as well as that black sooty mold that grows in the wake of their destruction.

You may find these little pests clustered underneath the leaves of your gardenia, where they tend to hang out in groups.

Aphids have lots of natural predators that help keep their populations to a minimum. If you see ants show up though, you need to get rid of them, or they will protect the aphids from other predators. A strong stream of water will dislodge most aphids, and insecticidal soaps and oils can be helpful in controlling a bad infestation.

Root Rot

This disease is caused by several fungal agents observed in gardenia plants, the most common being Phytophthora. Root rot can present as a general lack of health in the plant as a whole, or even on one side and not the other.

Other symptoms of root rot are yellowing of the leaves, starting with the oldest leaves, as well as leaf drop and wilt.

The only way to know for sure if the issue is root rot is to dig up the plant and examine the roots. If the feeder roots are brown and weak, your gardenia is probably facing root rot. Root rot is usually the result of poorly draining soil or overwatering.

Prevention is the best way to handle root rot. Make sure that you place your gardenia in a spot with good drainage, and always examine the roots of a new plant before putting it in the ground or a pot. If you have poor drainage in your area in general, planting in a raised bed can help.

Stem Canker

Stem canker is another fungal disease that is caused when the fungal pathogen Phomopsis gardinae enters the plant through wounds. The canker develops and eventually can develop a gall. These fungal spores are carried by water, and they can overwinter in the plant, making them difficult to deal with.

Plants found to have stem canker should be disposed of, and new plants should not be planted in the same area. The best prevention of this disease is proper gardening hygiene.

Make sure to always clean your tools before cutting into a new plant. Cross-contamination between plants can ruin a garden quickly.

Bud Drop

Bud drop is a collective name for any stress that causes the plant to drop its buds. This can be the result of a fungal or bacterial disease, as well as an infestation of insects. Over-fertilizing is another culprit of bud drop.

Powdery Mildew

This disease is caused by the fungus Erysiphe polygoni. It’s unfortunately quite common in gardenias. The fungus typically manifests as a greyish-white powdery coating on the tops of the leaves, especially new growth. This issue usually worsens during the hot summer months, and it can lead to the deformation of leaves and buds.

Humidity is a major factor in the prevalence of powdery mildew. Taking care to prune away dead branches and thin out any crossing branches in the interior of the plant will help to prevent it.

Proper spacing will also make a world of difference, as crowded plants tend to harbor more fungal-related diseases. Fungicides are also an effective preventative measure.