Gardenias are lush shrubs with waxy green leaves, showy and sweet-smelling flowers. Naturally, it is disheartening to see your Gardenia leaves curling up. The truth is, unlike the Snake plants which thrive on neglect, Gardenias need a lot of nurture and care.
Gardenia leaves curl up due to improper watering techniques, poor water quality, bad soil choice, temperature trauma and wrong humidity. In addition, pests such as aphids and spider mites, fungal infections can cause gardenia leaves to curl.
But do not worry. Through this article, we will explore the causes and learn several techniques to prevent it from happening to your plant.
Watering Techniques and Soil Issues
Underwatering
Gardenias originate from tropical climates. They love water and prefer moist soil. When you underwater them, the leaves curl and try to convey that they need more water.
In worse cases, they turn leggy or dry and sometimes die. If the leaves are yellow, brown, and crisp, the soil is dry to the touch and the shrub goes through bud drops, underwatering is the reason.
Though the plant is drought resistant, keeping the soil dry for extended periods can lead to the death of the plant.
Solution
- Regular, consistent watering is good for gardenias. Water the shrub every week with at least one inch of water. In winter, keep this as the maximum amount.
- Always confirm that the topmost inch of the soil is moist.
- Make sure that the soil is never too wet or too dry as that can make the leaves curl.
- You can also insulate the soil by using organic bark and mulch to retain the moisture.
- When possible, use rainwater or distilled water instead of tap water.
Overwatering Leading to Root Rot
Even though gardenias are moisture-loving plants, they have a threshold to how much water they can hold. Wet soils and excessive watering lacks oxygen and cause root injury.
The leaves droop and eventually drop. It can also lead to fungal diseases or decay in the roots. Rotten, smelly, or diseased roots cannot transmit essential nutrients and minerals to other parts of the plant.
This causes physiological malfunction and shows up on the leaves. The result is wilted, stunted, or curled up foliage.
Solution
- Gardenias need a minimum of 1 inch of good quality water each week. In winters and cold places, you can take this as the maximum threshold.
- The soil has to be damp. Not water-logged.
- If the soil feels wet after watering even a tiny bit, it could also be a soil-related issue.
- If the soil has fungus, loosen it up and repot it in fresh soil that is well-draining, rich, and full of nutrients.
- Pick a soil that is not too heavy. You can change the soil or add some sand, perlite, and organic matter to improve the drainage.
- The pot material also affects the watering schedule. For example, a terracotta pot loses water through its pores. So you need to adjust the watering schedule keeping that in mind.
- Be sure to check that the pot has enough drainage holes. The excess water needs to drain out. If not, the roots will rot.
Water Quality
Gardenias are intolerant to hard or alkaline water due to the presence of chemicals like chlorine, fluoride and other salts. Soft water contains excess sodium.
Using tap water over a long period results in salt build-up, where the plant suffers and dries. It also causes chlorosis, a byproduct of high sodium and chlorine in the water.
The leaves turn yellow, curl or wilt due to the lack of chlorophyll in them. Hard water also reduces the success rates of insecticidal soaps and concentrated mixes due to the presence of calcium, magnesium, and iron.
Solution
- Melted snow and rainwater is a great source of watering for gardenias
- Steer clear of softened water completely because it has high sodium levels.
- If you do not get rainwater easily, fill tap water in an open jug or container and leave it through the night. The excess chemicals in the water evaporate, making it ready for watering your plants.
- If none of this works, you can simply use distilled water each month to drain off the excess salts from your tap water.
- When spraying insecticidal soaps, remember to use distilled, bottled, or filtered water.
Soil Problems
A well-draining, acidic and nutrient-rich soil, free of nematodes is good for gardenias. Heavy or extremely clayey soils might become dense when you overwater them.
Overcrowding the soil with other plants will create competition in the soil and hinder root development. Gardenias also prefer moist soils.
If you use soil as the rooting medium for the plants, under wet conditions it will limit aeration and drainage. This will lead to root and soil-related diseases and show up on the leaves.
You should always mix with other insulating materials such as mulch to maintain soil health.
Solution
- Take note and remember that the soil pH has to be between 5.0 and 6.5. Maintain uniform soil moisture at all times and keep it acidic.
- Peat moss, wood shaving, shredded bark, and compost help in insulating the plants and prevents weed growths
- To maintain the pH levels, regularly fertilize your soil with acid reaction fertilizers.
- Use a slow-release, acidic fertilizer that is suitable for gardenia, and fertilize only twice a year. Once in early spring when the new growth happens and once in summer.
Temperature And Humidity
Temperature Trauma
Gardenias love warm temperatures because of their origin. Hence it is important to create such an environment for the plant. If the temperature drops below 60°F (15°C) at night, the leaves might curl.
Cold or freezing weathers shock the plant. If the temperature is too high and is greater than 90°F (32°C) during the day, or if the plant is receiving direct midday heat, leaf curling and scorching might occur.
Solution
- In the summers, you can keep the plant outdoors where the sun shines bright and full but not so directly on the plant that it scorches the leaves. During the winters though, bring them inside and place them in a warm and bright spot.
- Indoors, south or west-facing windows are the best spots for gardenias. But be sure not to keep them too close to the window glass as that can lead to leaf burning, browning and crispiness.
- Gardenias prefer 60°F (15°C) at night and a temperature between 70°F and 75°F (21°C-22°C) during the day.
- During the winters, you can use a winter room heater to create artificial warmth and temperature for your shrub.
Humidity Issues
Gardenias thrive and flourish when the humidity is at least above 50%. If you live in a cold place where the temperature drops below 60°F (15°C), and the air is dry during the winters, the moisture will reduce.
Plants draw water and nutrients through the roots and send out the excess through transpiration. When the humidity is low and the air circulation is close to zero, it’s impossible for plants to transpire normally. (Transpiration is a process where plants exhale water vapor through their stomata) To save itself from losing more water, the leaves curl up.
Solution
- One of the best ways to increase humidity is to run a humidifier close to the plant in the winters.
- You can also assemble plants and place them on plates of water with wet pebbles on them.
- Misting the plant helps replicate the environment in which the plant grows best. For optimum results, you can mist the plant once or twice a day, without the water touching the soil (too much water might contribute to soggy soil and eventually lead to root rot)
Pests And Diseases
Aphid Attacks
Aphids are pear-shaped insects that form clusters on the stems and deform the buds, blooms, and foliage. Another name for aphids is ‘plant lice.’
They ingest all the nutrients and sap from the leaves. The leaves curl and the growth stunts. Aphids also reproduce and multiply fast, making them difficult to treat. If your plant is blooming, aphid attacks result in sudden drops in quality and numbers.
Solution
- You should inspect the undersides of the leaves and wash them thoroughly using a water jet or hose.
- Individually pick out the aphids using soapy water and a soft brush or cloth.
- Applying an alcohol spray helps treat the leaves.
- You can also spray insecticidal soaps or horticultural oils on the leaves where the aphids hang around. Spray in intervals of five days to a week and take care to water the plants very well before this. A drought-induced plant will have a hard time coping with treatments.
- Always treat the plants only when the outside temperatures are below 90°F (32°C) and only late in the evening to prevent sudden shocks or injuries to the plant.
Spider Mites
Spider mites are extremely tiny and convincing that you wouldn’t know they are prime suspects when gardenia leaves to curl or wrinkle. The spider mites are hard to identify and appear reddish-brown.
They build fine thread-like strands of webs across the leaves and drink the sap of the plant. Unlike aphids, they cannot be easily picked out. In gardenias, spider mite attacks will cause white spots (stippling). Spider mites also like dry and dusty conditions.
Solution
- Make sure you place your plant in clean surroundings. Don’t allow any dust to settle on the leaves as that is a breeding ground for mites.
- To know if your plant has mites, place a paper underneath your plant and shake the leaves vigorously. If mites are present, they will move around rapidly indicating their presence.
- You can use miticides for the spider mites, but if they have laid egg sacs, the effect of the miticides will reduce significantly. You would then need to reapply them at five-day intervals during the summer and weekly intervals during the winter.
- Ensure that your plant has enough space and ability to breathe. When you overcrowd them with other taller plants, there is less light and becomes an open invitation for pests.
- Most importantly, spray until you are sure that all the spider mites have left. If necessary, do the leaf shake test.
Sooty Mold from Insect Infestations
Sooty mold is a black powdery coating on the leaves. When insects suck the sap in the plants and leaves, they let out an excretion which is the honeydew.
The result is a black or grey leaf. Sooty mold does not directly cause leaf curling, but the mold blocks sunlight and prevents photosynthesis.
It is also susceptible to other pest and flies attacks, diseases, and environmental issues due to its low immunity. This results in leaf curling, wilting, or dying.
Solution
- When you see sooty mold, simply use a wet rag and wipe the surface of the plant. The soot will come off, revealing the green, undamaged body of the leaf.
- Sooty mold is a result of insect infestation, so you should focus on controlling the insects rather than treating the fungus. Notice plants growing above and below your gardenia plant. Sometimes, insect-infested plants drip honeydew on a healthy plant.
- Apply horticultural oil to the leaves in the summer months. You can also use a cotton swab and medicated alcohol and remove the sap if they have dripped on the plants. Wash the plant with insecticidal soap and let them dry naturally.
Powdery Mildew
A white fuzzy mold, powdery mildew is a layer of fungus made up of many tiny spores on the leaves. They look like talcum powder and grow on the surface of the plant, leading to deformed leaves, flowers, and buds.
The fungus Erysiphe polygoni causes powdery mildew on gardenias. Powdery mildew begins growing in the summers and peaks at the end of the season. Since this affects fledgling leaves, it is much more important to take care of them as soon as you spot them.
Solution
- Keep the plant as close to the light as possible; confirm that there is enough air circulation and less humidity to prevent the growth of the fungus.
- Cut off infected leaves or stems.
- Apply fungicides to prevent the disease.
- You can even apply sulfur, potassium bicarbonate, or neem oil in the affected areas to soothe and treat the infection.
- Ensure that your plant is not overly moist to prevent powdery mildew
For the treatment of fungal diseases. Here are the fungicides I recommend:
| Name of The Fungicide | Amount | Amount of Water |
| Bonide 811 Copper 4E Fungicide | 1-4 tablespoons (.05-2.0 fl oz) | 1 gallon of water |
| Garden Safe Brand Fungicide3 | 2 tablespoons (1 fl oz) | 1 gallon of water |
| Southern Ag – Liquid Copper Fungicide | 3-4 tablespoons | 1 gallon of water |
Stem Canker
Cankers are long brown lesions that cause dents or swelling on the plant stems, especially close to the soil in a gardenia plant. The fungus Phomopsis gardeniae causes this and scarily, extends to the roots and leaves.
The leaves curl or wilt, turn less green, light yellow, and finally fall. This also leads to stunted growth. If the humidity is too high, the fungus spreads easily and causes diseases in the plant. In fact, it thrives in winter within the lesion.
Solution
- The first step is to prevent the plant from getting further injured. Cut out infected stems.
- Disinfect your garden shears between cuts and prune out the infected stems. You can use a solution that has more than 70% alcohol to sterilize your scissors. A bleach solution with 1 part bleach and 9 parts water is another way to keep your tools free of infection.
- Avoid stressing the plant further. Make sure you water or irrigate the plant only at the base of the soil, as water on the stems promotes fungal growth. A well-draining pot is also very helpful.
- If your plant is beyond repair, the only option is to let go of it.
Tips to Prevent Gardenia Leaves From Curling
- Gardenias enjoy moist soils.
- They prefer regular and consistent watering techniques.
- Keep away from hard and soft water.
- For insecticidal soaps, use distilled or bottled water.
- Make sure the soil is acidic; the soil pH has to be between 5 and 6.5
- Clear pest infestations as soon as you spot them.
- Disinfect your gardening tools between cuts.
- Keep your plant in clean conditions as dust nurtures spider mites.
- High humidity encourages fungal growth.
- Avoid planting your shrub in overly dense soils.
Final Words
Gardenias are a gardener’s challenge, so if your plant is not doing too well, that is normal. They are difficult even for experienced gardeners.
As long as you follow the instructions, keenly watch out for symptoms of infections, be wary of pest attacks and watering methods and create an environment that is close to its native environment, the plant will survive and thrive.