How to Grow Gardenias

Gardenias, also known as 'Chi Ti', are among the most aromatic flowers you can grow at home. However, they pose some challenges for gardeners. Gardenias require soil with a certain level of acidity, plenty of water, sunlight, cool temperatures, and high humidity. They are also prone to insect infestations. Yet, if you can overcome these challenges, you will be rewarded with fragrant, beautiful blooms that last from spring through summer.

Find a spot that gets direct sunlight or mild lighting. Unlike most plants, gardenias are delicate and particular about their environment.

• Gardenias thrive in areas with strong sunlight, high humidity, and even access to water and nutrients.
• Although they can survive indoors, hot, dry air and cloudy winter days may cause the plant to wither.
• The ideal time to plant gardenias is during the spring and fall, when the sun is bright but not too hot.
• Gardenias will not bloom if daytime temperatures exceed 21°C, or if nighttime temperatures go over 18.5°C or drop below 15.5°C.
• Keep in mind that gardenias cannot survive outdoors in winter. You should bring them inside when the cold weather arrives.

Check the soil's pH level to determine if gardenias can thrive in that location. pH measures the acidity of the soil, and gardenia roots cannot tolerate excessively high acidity levels.

• The pH scale ranges from 0 to 14, where 0 is the most acidic and 14 is the most alkaline. Gardenias prefer slightly acidic soil, so a pH of 5 or 6 is ideal as it represents moderate acidity.
• If needed, you can add sulfur, a white powder available at most garden stores, to lower the pH if it’s above 6.
• The soil should be rich in nutrients and well-drained. While gardenias require a lot of nutrients, their roots can rot if the soil is waterlogged.

Dig a hole that is just the right size for the root ball. Make sure the hole is 2 or 3 times wider because you will need space to cover the roots with soil afterward.

• The root ball includes both the plant's roots and the soil that surrounds them.
• If the soil is poor, mix in some compost before placing the root ball in the hole. Compost is organic matter that helps enrich the soil.
• Be mindful of where you plant your bushes. If you plant near your house, you can enjoy the fragrance of the flowers from your workspace or a window. However, planting too close to the house could lead to high pH levels, which are unsuitable for healthy growth.
• Keep in mind that gardenias require ample light, but cannot tolerate heat. It might be better to plant them near a bedroom window rather than a kitchen window.

Place the root ball into the hole. Cover the hole halfway with soil and water it.

• This step helps compact the soil and remove any air pockets. It's essential that the roots are snug in the soil so the plant can absorb water and nutrients effectively.
• If you plan to plant several gardenias, make sure each root ball is spaced about 0.9m to 1.8m apart. Gardenias can grow 0.6m to 2.4m in both height and width. Planting too closely can cause overcrowding, and the roots will compete for water and nutrients.

Fill the remaining hole with soil after the water has drained. Gently mound the soil around the root ball, leaving it slightly loose. Water carefully.

Water the plant with 2.5 cm of water each week. Typically, gardenias require around 2.5 cm of rainfall to grow properly, so use this as your guide when watering.

• Regularly monitor the moisture level of the soil, and water sufficiently when it becomes dry. Be careful not to overwater, as excessive moisture can deprive the roots of air.

Apply a 5-10 cm layer of organic mulch around the base of the plant. Mulch is made from decomposed organic materials such as leaves, bark, or compost, and is available at most garden stores.

• Mulch helps to enrich the soil, retain moisture, suppress weeds, and maintain a stable temperature for the soil.
• For optimal results, choose mulch made from wood chips, sawdust, or crushed bark.
• Applying mulch is crucial because gardenia roots are shallow and vulnerable to weed invasion.

Fertilize the plant with acid fertilizer every 3-4 weeks. Regular fertilization will encourage the plant to bloom properly.

• Ensure you use an acid-specific fertilizer. This type of fertilizer is specially formulated for acid-loving plants. Regular fertilizers may not provide adequate nutrition for gardenias.
• Be cautious not to over-fertilize, as this could harm the plant by causing salt build-up.

Spray the plant with mist daily. After ensuring the plant has enough light, soil, and water, you must also meet its humidity needs.

• Spraying mist will increase humidity around the plant, but it only lasts briefly. Therefore, misting should be done daily to ensure the plant thrives.
• In addition to misting, you can plant gardenias in clusters, but not too densely. This will create a more humid environment. To further increase humidity, you can place a dish of water near the plants. The evaporation will raise moisture around the gardenias.

Prune the plant in early spring to shape it. Remove any faded flowers to encourage further blooms.

• Pruning young and weaker plants will help stimulate blooming. Young plants are more resilient, and the lost branches are easier to recover as they haven’t fully matured.
• Trim off any unruly branches and spent flowers. Gardenias are woody shrubs, so cutting back older wood will encourage the growth of new branches.
• Remove any low branches that may touch the ground, as this could expose the plant to disease.
• Do not remove all the leaves. Leave some behind to allow the plant to nourish its roots.

Monitor the plant for whiteflies and scale insects. These pests are highly attracted to gardenias and can weaken or even kill the plant.

• Scale insects are gray, segmented pests that feed on the waxy parts of the gardenia, leaving a sticky residue on the plant. This causes new branches to die, and the plant becomes weak, losing its leaves.
• Whiteflies are tiny, white, mosquito-like insects that secrete a sugary substance, causing sooty mold to grow on it. This mold can lead to yellowing and leaf drop.

Apply a layer of insecticidal soap or horticultural oil if the plant is infested. These solutions kill both whiteflies and scale insects, and they are widely available at most garden centers.

• If the plant has a severe scale insect infestation, thoroughly cover the entire plant with the insecticidal soap or horticultural oil. Two days after the first application, carefully sprinkle beneficial fungi, such as Beauveria bassiana, onto the soil to target the root-feeding scale insects. Beauveria bassiana is also available at garden centers.

Cover the plant with a blanket or cardboard box during cold winter snaps. Gardenias are highly sensitive to cold temperatures and require protection from freezing winter winds.

• Ensure the cardboard box is large enough to cover the entire bush without bending its branches. You can add old blankets, straw, or bubble wrap underneath the box for additional insulation.
• Despite your efforts, the tips of the branches may still die and turn black from frost. In this case, use sharp pruning shears to trim off the damaged parts of the branches, cutting back a few centimeters below the affected area.
• Alternatively, you can repot the plant into a container and bring it indoors for the winter. While the plant may face a higher risk of pests indoors, you can follow specific care steps to keep your gardenia healthy in the house.

Place the plant in an area that receives direct sunlight for at least half a day. A south-facing window is ideal.

• Bringing a gardenia indoors during the winter when sunlight is scarce can be challenging. You may choose to supplement light with grow lights designed for plants.
• Gardenias also require a daytime temperature of 13°C and nighttime temperature of 18°C. Adjust the room temperature accordingly and monitor the plant's growth.
• Avoid placing the plant in cold drafts, and never position it near a heater. The dry air from a heater can cause your gardenia to lose its leaves—literally.

Water your plant once a week and fertilize it in spring and again in summer. Be sure to use acidic fertilizer for optimal growth.

• Water the plant when the soil feels dry to the touch, ensuring it is moist enough.
• Regularly check the pH level of the soil, ensuring it stays between 5 and 6. Use fertilizer specifically made for acid-loving plants that are flowering, such as one for azaleas, as it will be very effective.

Use a humidifier to increase moisture in the room. This is particularly important during winter.

• As mentioned earlier, you can group gardenia pots together and place a dish of water in the middle to increase humidity. However, be cautious when spraying mist on the plant, as combining misting with the humidifier can promote mold growth on the plant.
• You can also place the plant's root system directly on a tray of gravel and water. Start by adding a layer of gravel to the tray and filling it with just enough water to cover the gravel's surface. The gravel will keep the roots above the water while the evaporation process increases the humidity around the plant.

Prune your plant in spring to maintain the desired size. This will also encourage it to bloom beautifully.

• It’s best to prune the plant after the flowers have fallen off. Trim any dead branches until the plant reaches the size you want.

Regularly check for pests. When bringing a gardenia plant indoors, it can attract several types of pests beyond just whiteflies and mealybugs.

• One pest to watch for is aphids, small pear-shaped insects with legs and long antennae. You can treat these pests by spraying a mixture of one part liquid soap and one part water on both sides of the leaves. This method is also effective against mealybugs.
• Red spider mites are tiny and hard to spot with the naked eye. To check for them, gently shake the plant and catch any falling particles on a piece of white paper. If you notice red, yellow, brown, or green spots, your plant may have spider mites. Treat these pests with neem oil, a vegetable oil derived from the neem tree, available in most health food stores.
• Neem oil is also effective against the spread of the pests mentioned above. If the leaves are still yellowing after using these methods, your plant might be affected by root nematodes. These parasitic worms attack plant roots, and unfortunately, there is no known treatment for this disease.