Best Fertiliser for Hibiscus

The best fertiliser for hibiscus is a balanced, complete NPK for steady growth, paired with a higher-potassium, Ca/Mg-fortified formula during heavy bud cycles. Use
CompleteGrow NPK 20-20-20 as your dependable baseline, then rotate to
Advanced Formula NPK 4-18-38 + Calcium & Magnesium for stronger buds, colour and leaf strength.

What Hibiscus Need (NPK & Micros)

N (Nitrogen): Foliage and shoot growth. Too much = leafy plant, shy blooms.
P (Phosphorus): Root development and early bud initiation.
K (Potassium): Bud strength, colour, bloom longevity, stress tolerance.
Ca & Mg: Cell walls and chlorophyll. Prevents floppy growth and interveinal yellowing on new leaves.
Micros (Fe, Mn, Zn, B): Colour and enzyme function; availability drops in soggy or high-pH media.

Best Fertiliser Choices

Everyday growth & reliable flowering:
CompleteGrow NPK 20-20-20 — even NPK for balanced canopy, roots, and consistent bud set.
Peak bloom cycles / pale new leaves / bud drop:
Advanced Formula NPK 4-18-38 + Calcium & Magnesium — higher K for blooms plus Ca/Mg to firm leaves and petals.

Format tip: Liquids/solubles are best in pots (precise dosing, fast uptake). In-ground plants can use either, but always water in thoroughly.

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Feeding Schedule & How to Apply (Australia)

Spring: Start feeding every 2–3 weeks with 20-20-20 as growth restarts.
Summer: Maintain the cadence; rotate some feeds to 4-18-38 + CaMg during heavy bud/flower runs.
Autumn: Taper to every 3–4 weeks, then stop as growth slows.
Winter: Pause fertiliser. Water sparingly; protect below ~10 °C.

Pots vs In-Ground

Pots: Feed slightly more regularly (often every 2 weeks in warm weather). Flush each season to prevent salt build-up.
In-ground: Feed every 2–3 weeks and always water in well to move nutrients into the root zone.

Application Rules for Best Results

Apply on moist media, not bone-dry soil.
Always water through after feeding (soak to runoff in pots).
Keep a wet–dry rhythm (deep soak, partial dry-down).
Prioritise 6–8+ hours of sun — fertiliser can’t replace light.
Keep pH ~6–7; high pH locks out Fe/Mg and dulls colour.

Troubleshooting cues: Lush leaves, few flowers → reduce N and rotate to 4-18-38 + CaMg.
Pale new leaves → Ca/Mg/Fe issue or high pH → use CaMg-fortified formula and improve drainage.

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FAQs: Best Fertiliser for Hibiscus

What fertiliser makes hibiscus bloom best?
Consistent balanced feeding with NPK 20-20-20, then rotate to
4-18-38 + CaMg during peak bud cycles for stronger, longer-lasting blooms.

Liquid or granular?
Liquids/solubles are ideal for pots (precision, quick uptake). Either is fine in-ground if you water in thoroughly.

How often should I fertilise?
Every 2–3 weeks in spring–summer; taper in autumn; pause in winter.

I’m getting leaves but no flowers — is my fertiliser wrong?
Often it’s insufficient sun or too much nitrogen. Increase direct light and rotate to the higher-K 4-18-38 + CaMg during bloom runs.

New leaves look yellow between the veins — what now?
Likely Mg/Fe availability or high pH. Improve drainage, keep pH near neutral, and use CaMg-fortified feeding (4-18-38 + CaMg) until colour deepens.