What to Feed a Gardenia

Gardenias are heavy feeders that demand the right balance of nutrients to maintain their glossy leaves and prolific white blooms. Because they are acid-loving plants, they require fertilisers that lower soil pH and supply both macronutrients (NPK) and micronutrients like iron and magnesium. Feeding correctly is the difference between a lush, flowering gardenia and one with yellowing leaves and poor growth.

In Australia, gardenias typically flower from late spring through summer. To support this cycle, they need steady nutrition starting in spring. The ideal fertiliser for gardenias is one that provides nitrogen for leaf growth, phosphorus for flower development, and potassium for overall plant health — but in balanced amounts that do not push excess foliage at the expense of blooms.

Without regular feeding, gardenias quickly show signs of stress: yellow leaves, bud drop, or reduced flowering. A structured feeding schedule is essential for long-term health and beauty.

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Best Fertilisers and Feeding Schedule for Gardenias

The right fertiliser keeps gardenias green, vigorous, and heavy-flowering throughout the season.

Spring: Begin feeding as new growth emerges. Apply a complete fertiliser with an NPK balance such as 20-20-20, which delivers strong leaf and bud development.
Summer: Continue feeding every 4–6 weeks to maintain flower production. Supplement with liquid feeds for quicker uptake.
Autumn: Give a final feed after flowering to strengthen roots before winter dormancy.
Winter: Avoid heavy fertilising in cold months, as gardenias slow their growth.

Always water plants well before and after applying fertiliser to avoid root burn. Mulching with pine bark or sugarcane mulch helps maintain the acidic soil gardenias prefer and reduces nutrient loss. For potted gardenias, use half-strength liquid fertiliser more frequently, as nutrients leach faster in containers.

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FAQs: Feeding Gardenias

What is the best fertiliser for gardenias?
Use a balanced NPK fertiliser like CompleteGrow All Purpose NPK 20-20-20 or a product specifically formulated for acid-loving plants.

Can I use coffee grounds on gardenias?
Coffee grounds can slightly acidify soil but should never replace fertiliser. Use sparingly as a supplement, not as the main feed.

How often should I fertilise gardenias?
Every 4–6 weeks during the growing and flowering season. Container plants may need feeding more regularly at reduced strength.

What happens if I over-fertilise?
Too much fertiliser can cause leaf burn, bud drop, or excessive foliage growth with fewer flowers. Stick to recommended rates for best results.