Gardenia can also be planted outdoors in the spring or fall in the southern United States, or along the Pacific Coast. Gardeners typically purchase mature potted specimens for this purpose, so that they will bloom immediately. Should you choose to grow gardenia from seed, expect to wait two to three years before the plant flowers. Do note: Gardenia is toxic to pets and, if ingested, may produce mild diarrhea or vomiting. A well-tended gardenia grows compact with deep green leaves and will bloom in early spring or early summer, depending on its location. This plant prefers daytime temperatures of 75 to 82 F, so when growing gardenia indoors, you’ll need to keep it relatively warm. For this reason, outdoor potted plants need to be brought indoors on any night when the temperatures fall below the minimum.
Light
Indoor potted gardenias prefer bright light, but not direct sunlight, especially during summer. Placing them in a sunny window that gets afternoon shade is best. Garden gardenias grow best planted in a partially shaded location. Some sun, with afternoon shade, works well here, too.
Soil
Gardenias are acid-loving plants, preferring soil with a lower pH. Traditional potting mixes with a peat base usually meet this criterion. When planted outdoors, it’s best to test the soil’s pH and amend it as needed. A teaspoon of agricultural sulfur mixed into the planting hole may help lower soil pH.
Water
Gardenia prefers about one inch of water weekly (either by rain or by hand). Drip irrigation works best as it keeps water off the leaves, which can cause fungal leaf spots. Reduce watering in the winter and only keep the soil slightly moist to the touch. This winter watering method also works well for potted gardenia.
Temperature and Humidity
Gardenia requires temperatures above 60 F, free of cold drafts. This plant also prefers a high humidity level, above 60 percent. Indoor plants may require the use of a humidifier or constant misting during a cold, dry winter to maintain proper humidity.
Fertilizer
Feed garden gardenias in mid-March and then again in late June using an acid-rich fertilizer. Refer to the product’s instructed amounts and always mix the fertilizer either directly into the soil or dilute it with water. It’s best to use slightly under the recommended dosing to avoid over-fertilization. Stop feeding your gardenias in the fall to inhibit new growth before dormancy. Container plants can be fed about every three weeks with an acidifying fertilizer similar to the kind used on azaleas or camellias. Organic gardeners prefer blood meal, fish emulsion, or bone meal. Refer to product recommendations on amounts and test the soil’s pH regularly.
Types of Gardenias
This plant has been widely cultivated outdoors in warm climates. Many varieties are created from plant grafting onto a Gardenia thunbergia rootstock. The grafted plants tend to grow more vigorously, with larger blooms, but they are even less cold tolerant than undrafted species. Here are a few recommended cultivars:
Gardenia jasminoides ‘Aimee’ can grow up to 6 feet tall and bears huge 4- to 5-inch wide white flowers.Known as one of the best free-blooming varieties, the large shrub G. jasminoides ‘Fortuniana’ produces 4-inch blooms all season long.G. jasminoides ‘Buttons’ is a dwarf variety, growing 24 to 30 inches tall, and yielding 2-inch flowers.G. jasminoides ‘Crown Jewel’ grows in a 3-foot tall compact mound and bears 3-inch flowers. This plant is known to be hardy as far north as zone 6.
Pruning
Prune gardenias after the plants have stopped blooming, removing straggly branches and spent blooms to your liking. Gardenias don’t need to be pruned every season, however, as this variety does fine with an every-other-year cutback. When pruning, make sure to use sharp garden shears to shape back both the green and brown wood. Gardenias set buds on both new and old wood, so cutting either is fine.
Propagating
Gardenias are best propagated by rooting stem cuttings in the early spring, but gardeners find it more convenient to propagate from cuttings taken during pruning. Whichever you choose, make sure you give the new plant sufficient time to establish roots and grow before winter dormancy. Here’s how to propagate gardenia from cuttings:
How to Grow Gardenia From Seed
Gardenias can be propagated by seed, but it involves a long process that can take two to three years before the plant flowers. To do so, collect and clean seeds from dried seed pods and then dry them out for three to four weeks in a sunny window. Plant the seeds in a mixture of perlite and peat moss, barely covering them with about 1/8 inch of potting mix. Keep the seeds moist and out of the sunlight until they sprout (about four to six weeks). When the seedlings are several inches tall, transplant them into pots filled with peat-based potting soil, and continue growing them in a bright indoor location. Transplant the seedlings to your garden once they have a least three sets of leaves. Continue caring for the baby plants until they reach maturity.
Potting and Repotting Gardenia
When planted in containers, gardenias prefer a high-quality, peat-based potting mix with a low pH, similar to those formulated for rhododendrons. Gardenias are best repotted in the spring, as needed, when they begin to come out of winter dormancy. Determine if your plant needs repotting by first checking to see if it is root-bound (roots may be sticking out of the soil). You can also re-pot if your plant looks less vibrant but has no insects or diseases. Always step up your pot size and use a natural stone or terracotta pot. Both materials allow moisture to evaporate through their porous walls.
Overwintering
The tropical gardenia cannot tolerate temperatures that dip below 15 F and has a hard time dealing with winter frost. While USDA Zones 8 through 10 usually don’t experience this type of weather, it’s still a good idea to assure the warmth of your plant. To do so, provide an ample layer of mulch to the base of the plant to insulate its roots. You can also create a frost blanket on nights that are suspect. Frost cloth can be purchased at any nursery, or you can use a cardboard box, a bedsheet, or a 5-gallon bucket for this purpose.
Common Pests & Plant Diseases
Insects, especially scale, aphids, spider mites, mealybugs, and whiteflies can all affect the health of your gardenia, giving it its “high-maintenance” label. To control bugs, you can use a variety of horticultural oils and soaps, as well as organic products. Whichever you choose, arm yourself ahead of time for frequent infestations. Gardenias can also suffer from powdery mildew, leaf spot, dieback, anthracnose, and sooty mold, some of which can be treated with fungicides. In many instances, however, affected plants will need to be removed and destroyed, making this plant best suited for a gardener who enjoys the challenge of providing just the right conditions to deter most diseases.
How to Get Gardenia to Bloom
In order to maximize your gardenia’s blooms, you’ll need to make sure its growing conditions are spot on. Recommended fertilization and watering needs are the first steps to healthy blooms. Also, wait to prune your plant after the last blooms have faded. This way, you won’t cut back any growth on which new buds may form. Lastly, you can prevent “bud drop” (a condition known to affect this plant) by assuring humidity and water levels are just right (not too dry and not too moist).
Common Problems With Gardenia
Cold temperatures, inconsistent watering, poor soil drainage, and insufficient light can all cause bud and leaf drop on gardenias. Unsuitable environmental conditions can also cause yellowing leaves. Ultimately, any stress on the plant opens the door for pests, fungus, and disease to move in. Maintaining the ideal conditions for this plant is the ultimate challenge for gardeners. So, unless you live in a climate that can help the plant achieve perfect harmony, you may want to forego the beautiful gardenia for something more easygoing yet equally rewarding.
