How to grow and care for gardenias

Growing gardenias indoors

Growing gardenias indoors takes a little care but the results are well worth the effort. The most important points to remember are:

• Light: Place your gardenia in a bright position out of direct sunlight. In winter, move it to a brighter spot such as a south-facing windowsill so that it gets the maximum amount of sunlight – direct light at this time of year is not strong enough to burn the leaves.
•  Temperature: Gardenias prefer an even temperature between 15°C and 24°C during the day, and no lower than 15°C at night. Place them away from radiators and cold draughts.
•  Humidity: Keep the humidity level high around your gardenia by placing the pot on a saucer filled with pebbles covered with water.

Growing gardenias outdoors

In the UK, even hardy gardenias are best grown in pots so that they can be placed outside in summer and moved indoors in winter. In areas with very mild winters (above 10°C), hardy gardenias may survive outdoors all year.

Before moving potted gardenias outdoors for the summer, harden them off for a week or two by placing them outside during the day and bringing them back indoors at night.

Grow outdoor gardenias in a warm, sheltered spot in dappled shade. Water regularly to keep the compost moist.

Growing gardenias in containers

Gardenias grow well in containers, either indoors or outdoors, in summer.

1. Pot selection: Use a container with good drainage, approximately 5cm larger in diameter than the nursery pot. This allows space for growth without waterlogging.
2. Potting: Fill the pot with a specialised mix for acid-loving plants, such as a camellia and gardenia potting mix, or ericaceous compost. Remove the plant from its pot, lightly tease out the roots if congested, and plant it centrally. Backfill with potting mix to slightly below the rim of the pot.
3. Watering: Water thoroughly after planting, using tepid rainwater rather than tap water.

Gardenia care

1. Feeding:
   
   • Gardenias need regular feeding to maintain their glossy green foliage and fragrant blooms. Feed potted gardenias weekly in spring and summer with an ericaceous liquid feed or a slow release specialist feed. In winter, feed every 6 weeks.
2. Watering:
   
   • Water gardenias regularly in spring and summer to keep the compost moist but not waterlogged.
   • Use rainwater rather than tap water, especially in areas with hard water, and allow the water to reach room temperature before using so as not to chill the plant’s roots.
   • Water less frequently in winter, but don’t let the compost dry out completely between waterings.
3. Pruning and deadheading:
   
   • Remove spent flowers and any developing seed pods regularly to encourage continuous blooming.
   • Prune gardenias lightly in late winter to shape the plant.

How to grow gardenias from seed

Growing gardenias from seed can be difficult, but if you are up for a challenge, here’s how it’s done:

1. Soak the seeds in water for 24 hours before sowing.
2. Sow on the surface of a very free-draining mix of coir compost and perlite, lightly covering with 2-3mm of compost.
3. Place in a propagator at around 22°C and water regularly to keep compost moist. It can take up to 3 months for gardenia seeds to germinate.
4. Once the seedlings have developed two true leaves, pot on into individual pots filled with ericaceous compost.

Common gardenia problems

1. Whitefly, aphids and scale insects: These pests can be controlled with an insect spray, applied as needed
2. Sooty mould: This black fungal coating is caused by pests like aphids or scale. Treating the pests will help prevent and eliminate sooty mould.
3. Yellowing leaves: This is often due to overwatering but can also be a sign of iron deficiency caused by the compost pH level becoming too alkaline (a common problem if watering with tap water in hard water areas). Reduce watering if the compost is waterlogged, and apply an ericaceous feed containing chelated iron. Water with rainwater rather than tap water where possible.
4. Gardenias not flowering: This is often caused by high night temperatures (over 18°C) or dry air. Move the plant to a cooler spot and raise the humidity levels.