Gardenias are rather specific in their cultural requirements, and when their basic needs are not met, annual bloom can be minimal or skipped entirely. Gardenias require ample fertilization, bright filtered or indirect sunlight, specific overnight temperatures and ample moisture but not too much. Creating the optimal growing environment will help to induce a flowering cycle each year.
Position your gardenia plants in a location where they will receive bright filtered direct sunlight or bright indirect light. When grown indoors, give gardenias bright direct sunlight during the winter and spring months and bright indirect or filtered sunlight the rest of the year to prevent leaf burn.
Maintain daytime temperatures in the range of 68 to 74 degrees F and an overnight temperature of 60 to 62 degrees F to set buds for bloom.
Water your gardenias regularly to keep the soil moist at all times but not soaking wet. Water at the soil line around the root ball of the plant and never over the head of the plant to prevent leaf spot and disease.
Feed your gardenia once each month during the peak growing season from spring through mid-fall. Use an acid-rich formula complete fertilizer designed for gardenias, camellias or rhododendrons for garden grown gardenias such as a 30-10-10. Feed with a water-soluble balanced plant food such as a 10-10-10 when growing your gardenias as indoor plants.
Mix the acid-forming fertilizer or granular fertilizer into the soil or mix it with water. If you are using a pellet fertilizer, mix it into the soil around the plant.
Avoid getting any fertilizer on the leaves. Fertilize each month from April through November. If you are in southern Florida, fertilize monthly between March and October.
Apply water to the soil to avoid burning the roots.
Difficulty: Moderately Easy
- Acidifying fertilizer
- Peat moss
- Pine needles
- Pine nugget mulch
- Yellow sticky traps
Choose gardenia varieties that meet your height and space requirements. Mystery is a well-known variety that grows 6 to 8 feet tall. Radicans is a low-growing ground cover that reaches 1 foot in height with a spread of 3 feet.
Plant your gardenias in an area that gets full sun in the morning or filtered light all day. Overheating causes flower buds to drop off before they can bloom. Nighttime temperatures must be between 50 and 55 degrees for new flower buds to form.
Provide rich soil with a high acid content. Increase the acidity of the soil by fertilizing with an acidifying fertilizer, by amending the soil with peat moss and by using acidic mulch like pine needles or pine bark nuggets.
Increase the humidity gardenias love by misting the plant early in the day. Keep the soil moist, but not wet to avoid root rot.
Grow a hedge of gardenias close to the house to enjoy its fragrance indoors. If you wish to cut some blooms for indoor display, float them in a bowl of water, as the fragile stems do not take up water well.
Protect gardenias from the cold in northern climates by growing them in a sunroom or south-facing window. Gardenias do not survive winter in areas where temperatures drop below 15 degrees, but they grow well in pots in indoor areas with bright light and high humidity.
Watch for sooty mold growth on the leaves, an indication of whitefly infestation. Set out yellow sticky traps if your gardenias suffer from whiteflies.
Article courtesy of eHow.com
Remove faded flowers from the gardenia bush. According to Desert Tropical, “regular watering is necessary after blooming to keep the plants in good condition and able to withstand winter weather.”
Mound pine needle mulch around the base of the gardenia bush. If you have pine trees in your yard, rake fallen pine needles around the base of the bush.
Cover the pine needles with a regular mulch or a layer of decaying leaves. This prevents the pine needles from floating away in the rain.
Take cuttings from the tips of a gardenia shrub in the spring. Make the cuttings approximately 5 inches long and ensure there are at least two sets of leaves on the tip of the cutting. If there are leaves on the other end of the cutting, remove them.
Fill the container with a mixture of half sand and half peat moss. Insert the gardenia cutting several inches into the soil mixture with the cut side down.
Hold the container over the sink and water the cutting until water flows out the drainage hole in the bottom of the container. Place the container on the saucer when the water stops draining.
Place the plastic bag over the container and attach it securely by placing the rubber band around the top of the container over the plastic bag. Make two or three small slits in the bag with the scissors to prevent the cutting from decaying under the plastic. Place the container in a location that receives indirect light and is approximately 75 degrees.
Keep the cutting watered daily and wait for the cutting to root within four to six weeks. Once the cutting is growing well and you see abundant new growth, remove the plastic and watch to make sure the cutting continues to thrive.
When the new gardenia plant grows well without the plastic over the container and the outside temperature is at least 75 degrees, move the new gardenia plant to a sunny outside location.
Gardenias, like azaleas and rhododendrons, require a soil that is slightly acid; that is, with a low pH. A soil test kit should verify whether a soil mix is adequately acid for gardenias. If it is not, adding peat moss to the soil mix will render it more acidic.
Gardenias require good drainage, so a soil mix for growing gardenias should not be heavy or contain too much clay. Feeling the soil mix will confirm whether it is light enough for good drainage. Peat moss is a good amendment for a soil mix that is too heavy. Perlite is also an available amendment, but is not environmentally sustainable, and is thus not used by some gardeners. Sand can be a good substitute for perlite, if used in small amounts.
Gardenias require rich soil, with ample nutrients. Adding timed-release fertilizer and coffee grounds to increase acidity and add nutrients is normally necessary to make a soil mix optimal for growing gardenias.
Mold-related problems are the No. 1 cause of damage to gardenias, or poor plant performance. For this reason, ordinary garden dirt is not suitable as a soil mix for gardenias. Dirt from outdoors can harbor many forms of mold that can cause diseases in a plant that grows in humid conditions, as a gardenia does.
Purchasing vs Creating Soil Mix
Amending an existing commercial potting mix to be suitable for gardenias is the most efficient option for most gardeners. Soil mix can also be created by combining rich commercially purchased topsoil with fertilizer, peat moss, sand or perlite, and compost.
Conduct a soil test in the chosen area to verify that the pH level is between 5.0 to 6.0. Lower the pH level if necessary with sulfur, using the recommended amount from the results of the soil test.
Dig a hole twice as wide as the container and the same depth or height as the container. Mix the removed soil with a lb. of organic matter.
Remove the gardenia from the nursery container by pulling the container off the plant. Avoid pulling the stem from the container.
Place the root ball into the hole. Backfill halfway and then water to eliminate the air pockets. Finish backfilling once the water drains. Water well. Water 1 inch a week during the growing season if rainfall is absent.
Spread 2 to 4 inches of organic mulch such as pine bark around the gardenia bush to retain moisture and suppress weeds from growing.
Apply an acidifying fertilizer or fish emulsion once a month during the growing season. Follow the instructions on the label for correct usage.
Remove dead or diseased foliage as necessary to ward off pests. Deadhead flowers to persuade more blooms.
Outdoor Light Requirements
When planting gardenias outside, place them in full sun or partial shade. Any prolonged exposure to shade causes gardenias to reduce the number of flowering blooms during that growth cycle. Stay away from flower beds close to a house’s foundation or any other large structures that may block the gardenias from getting a good amount of light per day.
Indoor Light Requirements
If you want to enjoy your gardenias for longer and have your house filled with their sweet fragrance, you can plant them indoors in containers. Situate them near windows or patios to give them the best light possible. Placing them in these locations will also allow for air circulation and dispersal of their fragrance throughout your home. Give them full sun for most of the day when they are indoors.
When gardenias aren’t given enough light, a couple of problems can surface. They become stressed and experience bud drop, which is when unopened buds drop unexpectedly. Yellowing of gardenia leaves occurs with older leaves during early spring; however, when it occurs during other times of the year and to younger leaves, it is attributed to stress from insufficient light.
Giving gardenias the right amount of light allows them to grow and blossom the way nature intended. If they are given too much light, they can wither from the extreme heat and often experience sunburns on the leaves and blossoms. Avoid late afternoon sun during the hottest days of the summer as much as possible to stop this from happening. During the colder months, supplement the daily sunlight with artificial light to give the gardenias the right amount to last them through the winter.
In semi-tropical areas -- USDA zones 7b and above -- a gardenia grows as an evergreen shrub that shouldn't drop its leaves in the fall as other deciduous plants do. If your gardenia is dropping its leaves in this climate, it may be due to a disease or insect infestation.
Gardenias are susceptible to some insect infestations. White fly and mealy bugs are two of the most common and can cause leaves to yellow and fall. Check the plant occasionally for evidence of bugs and treat with an insecticidal soap to control them.
Keeping gardenias healthy prevents loss of leaves. Plant it in a location that receives either full sun or light shade with moist, well-drained soil. Gardenias are acid-loving plants and the pH of the soil should be between 5 and 6. In the early spring, prune it to the desired shape and give your gardenia plant food once a month when it is growing actively.
Water the plant well, until the surrounding soil is well-saturated. Watering the plant will nourish the plant, lessening the shock when the bloom is cut.
Clip the flower and stem from the plant. Use a clean pair of garden shears to cut the stem from the plant just before the stem meets its base. Cut the stem at a 45-degree angle to allow for more water penetration when the flower is placed in the vase.
Place cut gardenias immediately in a vase or other container filled with lukewarm water. Use a commercial flower preservative available from florists to extend the life of your flowers or prepare a homemade version by mixing lemon-lime soda with three parts water.