Bougainvillea Fertiliser Guide: Best NPK Ratio, Feeding Schedule & Flowering Tips

Bougainvilleas are famous for their vibrant colours, drought tolerance, and vigorous growth—but their stunning displays won’t happen without the right fertiliser strategy. These tropical climbers and shrubs need precise nutrient support to produce their iconic bracts and stay compact, lush, and healthy throughout the growing season.

Whether grown in pots, hanging baskets, or garden beds, bougainvillea requires balanced feeding and proper care to keep flowering. In this guide, you’ll learn:

The best NPK ratio for bougainvillea flowering and foliage
When and how often to fertilise for maximum blooms
Soil preparation, watering tips, and nutrient deficiency signs
Feeding differences for potted vs in-ground plants

Bougainvillea (Bougainvillea spp.) is widely grown across Australia for its brilliant, paper-like bracts in shades of pink, purple, orange, red, and white. But to get consistent, bold colour, feeding must support controlled growth and heavy flowering without encouraging excessive leafiness.

Let’s explore how to feed bougainvillea properly—from establishing strong roots to pushing vibrant, long-lasting blooms that brighten your outdoor space year-round.

Bougainvillea Fertiliser: Feeding Strategy Using CompleteGrow Products

Feeding bougainvillea is all about balance: too much nitrogen leads to leafy growth with few flowers, while low potassium can result in short, weak blooming periods. The key is to support consistent flowering while keeping vegetative growth under control—especially in pots or compact garden spaces.

Recommended Fertiliser Approach

Early growth (after planting): Apply a light dose of CompleteGrow 20-20-20 Liquid Fertiliser to support root development and general health
During active flowering: Continue using 20-20-20 at half strength every 2–3 weeks to encourage bud production without overfeeding
Ongoing maintenance: Use 20-20-20 monthly to keep the plant balanced and flowering throughout the warm season

Never use lawn fertilisers or high-nitrogen blends like 30-10-10—these promote excessive green growth at the expense of blooms. With bougainvillea, less is more when it comes to nitrogen.

How Often to Fertilise

Spring to early summer: Feed every 2–3 weeks with diluted 20-20-20 for new growth and flower initiation
Mid-summer to early autumn: Continue feeding at half strength to maintain flowering cycles
Late autumn to winter: Reduce to once every 6–8 weeks or stop entirely if growth slows down

Bougainvilleas flower in cycles and often bloom best after a slight environmental stress (such as a dry spell or cooler night). Strategic fertilising, full sun, and regular pruning together help maximise colour, bloom size, and duration.

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Bougainvillea Soil Mix, Watering & Deficiency Signs

Fertiliser is only part of the picture—bougainvilleas thrive in tough, well-draining soil. Too much moisture or poor drainage can lead to root rot, yellowing leaves, and reduced flowering, even if you are fertilising regularly. A strong foundation in soil and watering practices makes your fertiliser far more effective.

Best Soil Mix for Bougainvillea

Texture: Sandy, loamy, and well-drained
pH range: 5.5–6.5 (slightly acidic)
Additives: Perlite, coarse sand, or crushed granite help improve drainage

In containers, use a cactus or succulent mix blended with bark chips or fine gravel to maintain airflow around the roots. Bougainvilleas dislike soggy soil—always use pots with drainage holes and avoid water-trapping saucers.

Watering & Fertiliser Efficiency

Bougainvilleas bloom best when slightly stressed. Allow the soil to dry slightly between waterings, and reduce watering once flower buds appear. Overwatering not only encourages root problems but also dilutes fertiliser effectiveness, which can lead to weak growth and fewer blooms.

Signs Your Bougainvillea Needs Fertiliser

All leaves, no flowers: Too much nitrogen and not enough potassium
Light green or yellowing leaves: Often a sign of nitrogen or iron deficiency
Small flowers or short blooming cycles: Indicates low phosphorus or potassium availability

Stick to a consistent fertilising routine with a balanced feed like 20-20-20, and flush pots occasionally with plain water to prevent salt buildup if feeding frequently.

Fertilising Bougainvillea in Pots vs Garden Beds & Encouraging Flowers

Fertilising needs vary depending on whether your bougainvillea is growing in a container or directly in the ground. Potted bougainvilleas grow and bloom faster but require more frequent feeding, while in-ground plants develop deeper roots and need fewer applications with thorough watering.

Potted Bougainvillea Fertilising Tips

Frequency: Every 2 weeks during spring and summer
Dilution: Use liquid fertiliser at 50–75% strength for small containers
Type: Balanced liquid feed like 20-20-20

Flush with plain water every 6–8 weeks to avoid nutrient buildup, which can lead to leaf burn or reduced flowering. For best blooms, ensure your potted bougainvillea receives full sun and warmth.

In-Ground Bougainvillea Fertilising Tips

Frequency: Monthly or every 6 weeks during the active growing season
Application: Spread fertiliser evenly around the root zone rather than directly against the trunk
Watering: Deep soak after feeding to help nutrients penetrate the soil

How to Encourage Heavy Flowering

Allow slight dryness between waterings to trigger bloom cycles
Feed with 20-20-20 before and during flowering for vibrant colour and strong growth
Prune lightly after each bloom cycle to stimulate new flowering wood
Grow in full sun—at least 6 hours of direct sunlight daily for best performance

With consistent care, strategic watering, and regular feeding with CompleteGrow 20-20-20, bougainvilleas reward you with brilliant, long-lasting blooms from spring through early autumn.