Best Fertiliser for Rose Bushes

Rose bushes are the heart of many Australian gardens — timeless, hardy, and endlessly rewarding when cared for correctly. Their deep roots and flowering energy require balanced feeding throughout the growing season to maintain strong structure, lush foliage, and vibrant colour.

The key to healthy rose bushes lies in steady nutrient delivery, not heavy one-time feeding. A fertiliser that balances nitrogen, phosphorus, and potassium ensures even growth and consistent blooming. Using
CompleteGrow All Purpose NPK 20-20-20
for structure and
Advanced NPK 4-18-38 + Calcium & Magnesium
for bloom performance creates the ideal feeding rhythm for bush roses.

The Right Nutrient Ratio for Bush Roses

Bush roses rely on sturdy stems and dense leaves to sustain repeat flowering. Too much nitrogen can produce weak, leafy growth with fewer blooms, while insufficient potassium leads to small flowers and early petal drop. Balanced NPK ratios provide reliable performance through all growth phases.

Nitrogen (N)

Fuels healthy leaf and stem development, especially in spring. The 20-20-20 blend keeps canes thick and upright without overstimulating soft green shoots.

Phosphorus (P)

Strengthens roots and promotes new bud formation. In the 4-18-38 formula, higher phosphorus helps the plant recover quickly after pruning and ensures steady flower production.

Potassium (K)

Enhances flower size, colour intensity, and fragrance. Potassium-rich feeding builds resilience against heat, pests, and drought, keeping rose bushes vibrant in challenging conditions.

Together, these nutrients create dense foliage, sturdy canes, and full, richly coloured blooms — everything a strong rose bush needs to stay at its peak.

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How to Fertilise Rose Bushes Throughout the Year

Bush roses thrive on a regular, gentle feeding cycle. They respond best to smaller, frequent applications that keep nutrients moving through the soil rather than sporadic heavy doses. A simple, consistent schedule keeps foliage thick and flowers plentiful.

Spring: Begin feeding as buds swell and new shoots form. Apply 20-20-20 every 3–4 weeks to establish strong structure and encourage early growth.
Summer: Switch to 4-18-38 + CaMg to boost flowering intensity, colour, and fragrance. Continue every three weeks during active blooming.
Autumn: Feed lightly with 4-18-38 once monthly to help the plant store energy before dormancy.
Winter: Pause feeding after pruning. Resume in spring when new growth emerges.

Always water deeply before and after applying fertiliser to prevent root burn. Mulching after feeding helps retain moisture and keeps surface roots cool — particularly important in warmer climates. Roses grown near paving or fences benefit from extra watering to avoid nutrient loss from heat.

For young bushes, start with half-strength fertiliser until plants are well-established. Once roots spread, alternate between 20-20-20 and 4-18-38 for optimal results.

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Common Rose Bush Feeding Questions

Why are my rose leaves turning pale?
Usually a sign of nitrogen or magnesium deficiency. Feeding with 4-18-38 + CaMg restores leaf colour and strengthens growth.

Can I use the same fertiliser for all rose types?
Yes — both 20-20-20 and 4-18-38 blends suit bush, climbing, and standard roses. Adjust frequency, not product.

How often should I fertilise mature bushes?
Every 3–4 weeks through the growing season. Consistent feeding encourages healthy canes and prevents nutrient gaps that cause stunted blooms.

Is it safe to fertilise during hot weather?
Yes, if watered well before and after application. Avoid feeding in the middle of the day when soil is dry or hot.

Final Recommendation

Feed rose bushes with
CompleteGrow All Purpose NPK 20-20-20
for structural growth and
Advanced NPK 4-18-38 + Calcium & Magnesium
for flowering phases. Together they build resilience, colour depth, and strong root vitality — giving rose bushes the strength to bloom beautifully all season.