How Often to Fertilise Hibiscus

The simple rule: fertilise hibiscus every 2–3 weeks during spring–summer, taper in autumn, and pause in winter dormancy. Use a balanced feed for steady growth and rotate to a higher-potassium, Ca/Mg-fortified formula during heavy budding or if new leaves look pale.

Seasonal Feeding Schedule (Australia)

Spring (growth restart): Every 2–3 weeks with
CompleteGrow NPK 20-20-20. Resume deep wet–dry watering and light tip-pruning.
Early–Mid Summer (peak growth): Maintain 2–3-weekly feeding. If plants are setting lots of buds or you’re chasing colour, rotate some feeds to
Advanced Formula NPK 4-18-38 + Calcium & Magnesium (higher K + Ca/Mg).
Late Summer: Keep cadence steady; alternate 20-20-20 and 4-18-38 + CaMg as needed for bud retention and leaf strength.
Autumn (wind-down): Reduce frequency to every 3–4 weeks, then stop as temperatures drop and growth slows.
Winter (dormancy): Pause fertiliser. Water sparingly—just enough to prevent stem shrivel (<10 °C protection).

Pots vs In-Ground: How Often & How Much

Potted hibiscus: Feed slightly more regularly (every 2 weeks in warm weather). Liquids/solubles give precise dosing and faster uptake. Flush the pot each season to prevent salt build-up.
In-ground hibiscus: Feed every 2–3 weeks in spring–summer; water in thoroughly after each application to move nutrients into the root zone.

Mixing & application tips: Feed on moist media (not bone-dry); water through after feeding; keep pH ~6–7 for Fe/Mg availability; if leaves are lush but blooms are shy, reduce N and rotate to higher K (4-18-38 + CaMg).

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Which Fertiliser When?

Routine growth & general flowering:
CompleteGrow NPK 20-20-20 — even NPK for foliage, roots, and dependable bloom set.
Heavy budding, colour, or pale new leaves:
Advanced Formula NPK 4-18-38 + Calcium & Magnesium — higher K for buds/flowering; Ca/Mg for strong, green foliage and petal integrity.

Signs to Adjust Frequency

Lush leaves, few flowers: Too much N or not enough sun → keep cadence but rotate to higher K; increase direct light (6–8+ hrs).
Pale new leaves (interveinal chlorosis): Likely Mg/Fe availability issue or high pH → use 4-18-38 + CaMg; check drainage and pH.
Tip burn/salt crust on soil: Over-feeding or poor leaching → flush pot heavily, resume at label rates.
Slow growth despite feeding: Usually low light, waterlogging, or compact mix → fix root-zone first, then continue schedule.

Quick Application Rules

Fertilise on a 2–3-weekly cadence in active seasons.
Always water through after feeding.
Maintain a deep wet–dry watering rhythm.
Flush pots each season to prevent salt build-up.
Prioritise sunlight—fertiliser can’t replace 6–8+ hrs of direct sun.

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FAQs: How Often to Fertilise Hibiscus

How often should I fertilise hibiscus in pots?
Every 2 weeks in warm weather; every 2–3 weeks otherwise. Flush pots seasonally to avoid salt build-up.

How often for hibiscus in the ground?
Every 2–3 weeks in spring–summer, then taper in autumn and pause in winter.

What should I use for regular feeds?
CompleteGrow NPK 20-20-20 as the dependable baseline. Rotate to
4-18-38 + CaMg during heavy budding or if new leaves pale.

Can I fertilise weekly?
Only at reduced dose and with excellent drainage; most home growers get best results on a 2–3-weekly schedule to avoid salt build-up.

Do I fertilise in winter?
No—pause during dormancy. Resume in spring as new growth starts.