How To Grow And Care For Gardenias

No plant expresses the grace of the South better than gardenia. Intensely fragrant white blossoms contrast beautifully with shiny, leathery dark green leaves. The double forms make for classic corsage flowers. Gardenias should be planted in the fall after the first frost or in spring in colder climates, for gorgeous blooms throughout the spring, summer, and for some cultivars, the fall. Note that all parts of gardenias are known to be toxic to dogs, cats, and horses.

Plant Attributes

How To Care for Gardenias

The best time to plant gardenias is fall, or six weeks before the first frost in milder climates, and spring for areas with colder temperatures, depending on your location.

For larger varieties, gardenias grow as border plants or in areas where they won't compete for the soil's nutrients, are overcrowded, and have room for their roots to spread. Also, you should try not to disturb these plants once in place. Plant them high in the ground or on raised beds, similar to azaleas and rhododendrons, allowing for better drainage and altering soil composition.

Gardenias do well in large pots on decks and patios. Gardeners in cold-winter areas can grow them in cool greenhouses. Unfortunately, they make poor houseplants as they attract mites, mealybugs, and whiteflies.

Light

Plant gardenias in a place where they can get four to six hours of sunlight, with some caveats. In warmer climates, avoid the intensity of late afternoon sunlight and choose an area where it can receive only morning to mid-day light. Cooler temperature regions can use a site with full sun.

Soil

Gardenias prefer acidic (5.0 to 6.5), organically rich, and loamy soil that's well-draining. You can amend your soil to increase acidity and add organically rich materials like compost, manure, ground bark, and sphagnum peat moss.

Water

Although gardenias enjoy sunlight, they can't go too long without proper watering. Gardenias need an inch of water per week to stay happy. Gardenias prefer rich, acidic soil, similar to rhododendrons and azaleas, that doesn't stay too wet, so it's a perfect option for Southern gardens.

Temperature And Humidity

This shrub holds up in humid temperatures, preferably a humidity level of around 60%, which wards off spider mites who take over gardenias in dry conditions. Since gardenias need humid conditions to flourish, remember to water or mist your gardenias if there is a prolonged drought.

During their growing and blooming season, day temperatures between 65ºF and 70ºF and night temperatures between 60ºF and 65ºF are ideal. Gardenias can't tolerate cold temperatures below 15ºF and may get damaged or die if these cold temps linger. There are many varieties now, like 'Frostproof', that can be grown in Zone 7 where temperatures can dip to 10ºF in the winter.

Fertilizer

Fertilize gardenia in early spring, after the last frost of the winter. Feed plants every three to four weeks during the growing season—use an acidic, slow-release fertilizer. Fish emulsion, blood meal, or even coffee grounds will also work. Feed potted plants just as often and test soil pH levels to maintain good health.

Type Of Gardenias

• 'August Beauty': This plant grows 4 to 6 feet high and 3 to 4 feet wide, and blooms heavily in mid-spring and into fall with large double flowers.
  
• 'Golden Magic': This variety reaches 3 feet tall and 2 feet wide in two to three years, eventually larger. Extra-full flowers open white and gradually age to deep golden yellow, blooming from spring through summer, and peaking in mid-spring.
• 'Kimura Shikazaki' ('Four Seasons'): A compact plant, it grows 2 to 3 feet tall. Its flowers are similar to those of 'Veitchii' but slightly less fragrant. This variety has an extremely long bloom season, blooming from spring to fall.
• 'Mystery': This is the best-known selection of gardenia, bearing 4 to 5-inch double flowers from mid-to-late spring. It tends to be rangy and needs pruning to keep it neat. It can reach 6 to 8 feet high and wide.
• 'Radicans' ('Prostrata'): This selection grows 6 to 12 inches tall and spreads to 2 to 3 feet, with small leaves and inch-wide double flowers blooms in the summer. It's suitable for small-scale ground cover or pots. However, it is not cold-hardy or suited for the Middle South.
• 'Veitchii': This compact, and reliable grower reaches 3 1/2 to 4 1/2 feet tall and 3 feet wide. It blooms prolifically from mid-spring into fall (sometimes even during warm winters), bearing 2 to 3-inch flowers.
• 'White Gem': At just 1 to 2 feet tall and wide, this selection is helpful for edgings, containers, or raised beds, where the fragrance is appreciated even from a single, creamy white summer flower.

Pruning

Remove faded or dying flowers, usually around two-thirds from their initial flourish, to continue seeing blooms. You can prune younger gardenias to adjust their shape or to remove straggly branches and faded flowers. Avoid pruning in the winter when buds are forming.

Propagating Gardenias

The best time to propagate gardenias is in spring. Cutting gardenia will help control the size of your bush to your liking, ensuring a neat look. While you're cutting it back, you might as well take a few cuttings to propagate some new plants. Gardenias can be propagated through the following method:

1. Cut the branch down from the tip with pruners, about 5 inches; the stem should preferably be green at this end, called softwood.
2. Remove all but three leaves at the top with pruners.
3. To encourage root growth, dip the bottom of the cut stem in root hormone.
4. Plant in a 3-inch pot filled with a mix of potting soil and perlite.
5. Keep the pot in a humid spot with indirect sun, making sure the soil is evenly moist.
6. The cutting will take four to six weeks to root before it can be transferred to the ground.

How to Grow Gardenia From Seed

When planted from seed, gardenias will take two to three years before they begin flowering. So, if you're looking for quick results, purchasing a gardenia that is already grown or propagating from an already-established gardenia bush is best. Follow these steps to grow gardenia from seeds:

1. Collect dried seed pods that have fallen from your existing gardenia shrub.
2. Extract the seeds from the seed pod.
3. Quickly wash the seeds under cool water to remove any seed pod residue. Then, place the seeds on a paper towel and pat them until they are dry.
4. Allow the seeds to dry on a windowsill with lots of sunlight for three to four weeks.
5. Plant the seeds in a 4-inch pot with drainage holes in an equal mix of perlite and moss, covering each seed with only 1/8 inch of the soil mix.
6. Water the pot until it's thoroughly dampened, about 2 inches of water.
7. Keep moist and out of direct sunlight for about four to six weeks to allow germination to occur.
8. Once your seedlings have three sets of leaves, you'll need to transplant them to a bigger container with adequate drainage or your garden.
   

Potting And Repotting Gardenia

Gardenias do well outdoors in containers and can even be pruned into topiaries. For first-time potting, use a container slightly larger than the one from the nursery that has drainage holes. Like growing gardenias in the ground, acidic, well-draining, evenly moist soil is required. But for containers, use basic potting mix, which is slightly acidic and well-draining. Add an acid plant fertilizer to the soil, and continue to feed once a month. Repot gardenias every two to three years.

Overwintering Gardenia

Gardenias will experience cold damage when temps drop below 15°F. To prevent cold damage from occurring, we recommend adding mulch around your gardenia shrubs for insulation before winter begins. On days when you know the temperature is going to drop into the damage zone, cover the shrubs with a frost blanket to help protect them.

Outdoor container-bound gardenias should be moved to a covered, insulated area for the duration of the cold snap. This is a good solution for an area that occasionally drops in temperature. However, if you live in a colder climate with near-constant freezing temps in the winter, gardenias in containers should be brought inside.

In this case, place gardenias near a south-facing window that receives lots of sunlight. Do not prune gardenias during this time to prevent accidentally trimming off growing buds. Be sure not to overwater your gardenia, however, keep the plant moist. Mist gardenia daily and keep it moist and away from direct airflow.

Common Pests & Plant Diseases

Pests

You can control whiteflies, aphids, and other sucking insects with light horticultural oil. Try using an insecticide rinse to wash away the residue left behind.

Root Rot

When the leaves of your gardenia turn yellow, it is a sign that you might have root rot. This damage typically occurs from overwatering or another fungus in the soil, such as powdery mildew. Powdery mildew appears as white spores covering the plant's leaves and can be a recurring problem preventing future growth. We recommend using neem oil or another organic fungicide to treat it on your gardenia.

How To Get Gardenias To Bloom

Maintaining healthy gardenias encourages more blooms. Here are some best practices to keep gardenias blooming all season, according to Southern Living Plants:

• Fertilize gardenias each spring after the last frost, then feed regularly during the growing season.
• Ensure the soil is evenly moist, but don't overwater, which can cause root rot.
• Mulch the roots to help maintain moisture.
• Gardenias don't need a lot of pruning, but if you need some shaping or want to remove unproductive stems, do so after the blooming period, in early summer, but before the budding period, which starts in late summer and fall.
• Gardenias bloom in summer and fall, and the bloomed flowers can last several weeks.
• Deadhead the spent blooms to encourage more flowering and maintain a tidier-looking plant.

Common Problems With Gardenias

Bud Reductions

There are several reasons why your gardenia might not be blooming to its full potential. Along with insects and disease, improperly managing your plant, such as over or under-watering, can result in the plant's failure. When temperatures, specifically the humidity, drop, it can harm the gardenias.

Black Leaves

When gardenias are infested with aphids or whiteflies, these bugs secrete a sticky honeydew as they feed. Black, sooty mold then grows on the honeydew. Spray your gardenias according to label directions with horticultural oil, making sure to wet both the tops and undersides of the leaves, as well as the stems. This will kill the insects, which will also knock out the moldy honeydew.

Yellow Leaves With Green Veins

If your gardenia has yellow leaves with green veins it is due to a condition called chlorosis brought on by a lack of iron in the soil. Acid soils have plenty of available iron. Alkaline soils do not. Apply garden sulfur to the soil to acidify it or feed with an acid-forming fertilizer like Espoma Holly-tone.

Yellow Leaves Dropping

This is part of the normal growth cycle of the plant, usually happening in the spring. Even on evergreens, leaves only last a couple of years, so you will see old leaves dropping, but new ones will replace them.