What is the Best Fertiliser for Clematis? A Seasonal Feeding Guide for Australian Gardens

If you’re wondering what is the best fertiliser for clematis, you’re not alone. Clematis are one of the most beloved flowering vines in Australia, offering stunning vertical displays from fences to pergolas. But while their blooms are bold, their feeding needs are surprisingly specific—especially if you want consistent flowering and strong stem development year after year.

Clematis varieties—from large-flowered hybrids like ‘Jackmanii’ to species like Clematis montana or C. armandii—require balanced nutrition to power both foliage and flowering cycles. Poor feeding leads to weak stems, reduced bloom count, and patchy regrowth in spring. This guide explains how to feed clematis correctly and why a high-quality, balanced NPK fertiliser is essential for lasting performance.

Understanding Clematis Growth & Soil Needs

Clematis is a perennial, climbing plant with a deep-root system and vigorous top growth. Its feeding needs shift depending on growth stage:

Spring (emergence): Nutrient demand spikes as buds open and stems extend
Early summer: Peak flowering stage—requires extra potassium for bloom support
Late summer/autumn: Light feeding supports root growth before dormancy

Clematis thrive in rich, well-drained soil with a neutral to slightly alkaline pH (6.5–7.5). Soil that is too acidic or dry will lead to yellowing and leaf drop—no matter how much you feed.

What Is the Best Fertiliser for Clematis?

The ideal choice for both flowering and foliage is CompleteGrow NPK 20-20-20 Fertiliser. This balanced, water-soluble fertiliser gives clematis everything they need in the right ratios:

20% Nitrogen – Supports vigorous green stem and leaf growth early in the season
20% Phosphorus – Encourages root mass and overall plant health
20% Potassium – Enhances flowering, petal colour, and resistance to stress

Unlike fertilisers that are too high in nitrogen (which leads to excess leaf growth), this formula keeps the plant balanced throughout the growing season.

Feeding Schedule for Clematis in Australia

Late Winter (Aug): Apply 1 tablespoon per plant to support spring bud development
Spring (Sep–Nov): Feed every 3–4 weeks as new stems grow and blooms emerge
Summer (Dec–Jan): Continue feeding monthly to encourage repeat flowering
Autumn (Mar–Apr): Light feeding helps strengthen roots before winter dormancy

For container-grown clematis, use half the amount every 2–3 weeks and ensure regular watering. Always apply fertiliser to moist soil and avoid contact with dry roots.

Common Clematis Feeding Issues

Even if you’re using the best fertiliser for clematis, improper timing or soil issues can affect results. Watch for these signs:

Yellow leaves: Often caused by nitrogen or magnesium deficiency
Poor flowering: Usually due to low potassium or over-pruning late in the season
Dieback or weak growth: Can result from dry soil, root rot, or inconsistent feeding

Always mulch around the base to keep roots cool and feed consistently through the growing season.

FAQs: Fertilising Clematis

Can I use tomato or rose fertiliser on clematis?

You can—but balanced formulas like NPK 20-20-20 offer more consistent results across the season, especially for spring-emerging clematis varieties.

How often should I feed clematis?

Feed monthly during spring and summer. Reduce frequency in autumn and stop completely during dormancy.

What’s the best fertiliser for clematis in pots?

The same NPK 20-20-20 formula, used at half strength every 2–3 weeks. Be sure to water regularly and flush excess salts if needed.

Feed Your Clematis Right & Watch It Thrive

Using the best fertiliser for clematis makes all the difference in bloom size, quantity, and overall plant health. With CompleteGrow NPK 20-20-20, you’ll give your clematis everything it needs to flower prolifically and climb strong, year after year.

Browse our gardening guides for more flowering plant tips, or speak with our plant care team for tailored support.