How to fix your gardenia's yellow leaves and other care tips (2025)

Gardenias are one of the most beautiful, fragrant flowers to bloom in summer, with beautiful white flowers and glossy green leaves. But if your gardenia has yellow leaves, it’s a sign that something isn’t right.

Here, we run through some of the main reasons for yellow leaves on a gardenia, as well as how to treat it. We also go through reasons its flowers may drop off and other common issues that can take hold during winter and early spring when there are more drops in temperature.

Why are my gardenia leaves yellow?

If your gardenia’s yellow leaves show up in the warmer months, it’s likely to be a lack of iron, magnesium or both.

There are also a few signs you can look for to determine what type of mineral deficiency is causing your gardenia’s yellow leaves.

• Magnesium deficiency: This affects old leaves first, so they may turn yellow before dropping from your gardenia. To treat this, sprinkle a teaspoon of Epsom salts around the plant and water it.
• Iron deficiency: If new leaves on your gardenia are yellow or dropping from the plant, it’s likely to be from iron deficiency. You can treat it by applying iron chelates to the plant, ideally in late spring and again in summer.

Other ways to treat gardenia yellow leaves

While mineral deficiencies are a common cause of yellow leaves on a gardenia, factors including how much water, sunlight and even the type of soil can also have an impact on your plant’s leaves. So, here are some other steps you can take to treat yellow leaves:

1. Consider how often you water your gardenia

Yellow leaves can be a sign of over-watering or under-watering your plant. Check the moisture levels on the surface of the soil and try adjusting how often you water it.

2. Check the soil composition

Gardenias do best in well-drained soil, so it’s good to consider this before planting one. If you have a relatively new gardenia with yellow leaves, check the soil around it to see if it’s draining. If it’s dense or soggy, you could try adjusting your watering schedule or even consider re-planting it.

3. Check the weather

Gardenias don’t like extreme changes in temperature, especially when it gets cold. So if you suddenly notice yellow leaves, it could be because of the temperature – and the weather can help you determine that.

Ideally, aim to plant your gardenia in a spot that’s mostly sunny, or gets some shade in the afternoons. You could also consider planting it in a sunny corner by a wall or other windbreak that could help protect it from cold snaps.

Can I prune gardenia yellow leaves after treatment?

If you have determined the reason for your gardenia’s yellow leaves and treated it, you can consider pruning off the affected area. Just keep in mind how many of the leaves are yellow, and whether they are old or new leaves before removing too many of the leaves. That way you can balance caring for the plant and getting the visual impact you want.

Why are my gardenia leaves dropping off?

Older, lower leaves fall as new leaves and shoots are produced in warm weather, so don’t panic if it’s the change of season. You can also expect some winter leaf drop in cooler climates.

Why have my gardenia leaves turned black?

Sooty mould is a harmless fungus that coats leaves that grows on honeydew, a sticky, sweet substance excreted by scale and mealybug. To protect your leaves from this fungus, spray the entire plant with a horticultural spray oil. The mould will crumble away or use a soft cloth and soapy water to gently remove it.

How to take care of gardenias in Australia

These leafy flowering shrubs are found in warm climates, which make them perfect for Australian gardens. Gardenias love a warm sunny or partly shady spot in acidic soil that is watered weekly on average. Warmer days mean the plant will need need more frequent watering, but be careful not to overwater!

Most varieties of gardenia also need an acidic soil between pH 4.5 and 5.5. The Tahitian gardenia (G. taitensis) is the only species that copes with alkaline soils, but it can be hard to find and requires a warm climate.

Feed gardenias monthly from late spring to the end of summer, when they actively take up nutrients. Use poultry manure sparingly or feed with a flower and fruit fertiliser or seaweed tonic.

Gardenias also require protection from intense sun during Australian summers. A large shade tree, like a jacaranda or poinciana tree, is good for protecting gardenias from direct heat.

How to make a neutral soil more acidic

To make a neutral soil more acidic, you can watering on iron chelates once or twice each year in late spring, summer or early autumn. Alternatively, you can rake in one handful of powdered sulfur per square metre in late spring or a month before planting, and mulch regularly with pine or she-oak needles to gradually acidify the soil.

Gardenias need daytime temperatures above 10–15°C to start flowering, which is why many of the flower buds that form in warm autumn weather succumb to colder winter temperatures and drop off.

When do gardenias flower in Australia?

Gardenias flower in summer, but also spot-flowers in spring and autumn.

Why have my gardenia’s flower buds dropped off?

Overwatering, drought, inadequate sun, or high or low night temperatures can be the problem. To mediate this, choose an ideal location and provide consistent care, and this may mean repotting or moving its planter.

Flower buds dropping off may also be a result of sap-sucking pests such as thrips or aphids. Try spraying buds and flowers with a horticultural spray oil three times in spring or summer, three weeks apart, and this should deter the pests.

Why didn’t my gardenia flower?

Gardenias flower on new growth. Prune or shape your gardenia plants, especially hedges, in late August at the latest.

Why do gardenia flowers turn brown?

Flowers naturally darken from white to yellow as they mature, and drought and intense sun cause flowers to burn, brown and crisp. If it is the latter, protect gardenias from hot afternoon sun, especially in inland, tropical or subtropical climates.

Best regions for growing gardenias in Australia

Coastal regions best suited to gardenias occur from Perth and Sydney northwards. But in these locations, they need to be protected from salt-laden sea breezes.

For Victorian and South Australian gardeners, the gardenia cultivar ‘Grandiflora Star’ is a good choice. In the tropics, subtropics and inland regions, gardenias can have too much sunshine, and last longer in spots where they receive dappled afternoon shade.

The Tahitian gardenia (G. taitensis) is the only species that copes with alkaline soils, but it can be hard to find and requires a warm climate.

How to grow gardenias in containers

Gardenias are ideal for containers or garden borders. These shallow-rooted plants love frost-free, humid climates and grow best in well-dug, freely draining, compost-enriched, acidic soil. They love plenty of well-rotted manure, compost or a half-and-half mixture of both before planting, which you can fork into the top 30–45cm of soil before you plant.

In subsequent years, mulch the plant with a 10cm layer of compost in spring to supplement the organic content of soil, as compost is great for encouraging earthworm activity. Alternatively, you can mulch with straw, lucerne, sugarcane or hay, but it’s best to keep it away from the base of the plants to avoid stem rot.

How to grow gardenias in pots

The best way to enjoy gardenias in cool or inland regions is to grow them in pots. This allows you to move them to a sunny, sheltered position in winter, or a cooler spot with afternoon shade in summer.

Plastic or ceramic pots are preferable to terracotta or concrete as they don’t allow the potting mix to dry out as rapidly. Use a potting mix for acid-loving plants.

Gardenias relish even moisture, but their roots rapidly rot in poorly drained soils, so if you use saucers under your pots always tip any water out of them.

How to repot gardenias

During the warmer months, gardenias grow steadily, and in southern Australia this may mean re-potting only every other year at the most.

Congested roots stunt growth, and damaging their roots during re-potting can cause flower buds to drop. Planting, transplanting and repotting are best completed in spring.

Other insights on gardenias

• The genus Gardenia includes about 60 species from the tropics and subtropics of Africa, Asia, Australia and the Pacific.
• This small tree grows up to 5m high with large, short-lived, richly perfumed flowers. It has two mass flowerings, in spring and again in summer. But the number one gardenia is the common gardenia,Gardenia jasminoides(formerlyG. augusta), a native of China and Japan.
• ‘Florida’ is the main variety grown, with the larger ‘Magnifica’ and the low-growing ‘Radicans’ coming second and third.

Popular cultivars

• ‘Florida’
• ‘Gold Magic’
• ‘Four Seasons’
• ‘Professor Pucci’