Fertilising guide
How to fertilise Clematis (Clematis spp.)— schedule & NPK
Also called Clematis, Leather flower, Virgin's bower, Old man's beard, Traveller's joy.
More about clematis
About Clematis
Clematis spp. · also called Clematis, Leather flower · flowering
Clematis is a deciduous or evergreen flowering climber prized for showy blooms on trellises, walls and fences. It thrives with sun on its foliage and shade on its roots. Important warning: Clematis is toxic to cats, dogs and horses per the ASPCA, so site it away from pets that chew foliage.
Growth habit: Mostly woody, deciduous climbing vines (some evergreen or herbaceous), climbing without clinging by twining their leaf stalks around supports such as trellises, wires, other plants or shrubs. They do not damage building exteriors. For pruning, clematis fall into three groups based on flowering time and the age of flowering wood: Group 1 (early, prune after flowering), Group 2 (large-flowered hybrids), and Group 3 (late-flowering, hard-prune in late winter/early spring).
Watch for — Aphids: Sap-sucking insects cluster at shoot tips, stunting growth and coating foliage in sticky honeydew that can develop black sooty mould.
What fertiliser clematis actually wants — and why
Clematis flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.
Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for clematis: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed clematis, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For clematis:
Clematis in fertile ground soil need little feeding; an annual spring mulch of a 5-7.5cm (2-3in) layer of organic matter is usually enough. The RHS recommends feeding container-grown clematis throughout spring and summer with an organic-based, general-purpose liquid fertiliser. Avoid high-nitrogen feeds, which encourage leaf at the expense of flowers. In practice: no routine feeding at all for clematis — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.
The dormant-season rule matters more than the exact interval: skip feeding entirely when clematis is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for clematis
None is the correct answer for clematis. The flower-versus-foliage trade-off is the whole point: hold back and you get the display.
Feeding always goes onto already-damp soil, never dry roots — water clematis first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the clematis watering schedule.
Signs you are over-feeding clematis
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for clematis:
- Abundant leafy growth and very few flowers (the classic over-rich symptom).
- Soft, floppy stems and a sprawling, leafy habit.
- Scorched edges and salt crust if it has been fed in a container.
Signs you are under-feeding clematis
- Effectively never an issue — these plants flower on poverty.
- Only on genuinely dead soil: weak, thin growth and few blooms.
- A short-lived plant in completely spent container compost.
If the symptoms point at watering, light or roots rather than nutrition, the full clematis care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
If clematis has accidentally been fed and is all leaf, a plain-water flush plus a move to leaner soil resets it; otherwise no flushing is needed because you are not feeding it.
Organic vs synthetic feeds for clematis
Organic options
A thin compost mulch for soil structure is the absolute most; mostly, give it nothing. UK/US: leave it lean — no manure, no liquid feed. Poor soil is the active ingredient here.
Synthetic / liquid feeds
None. Synthetic feeds, particularly anything with appreciable nitrogen, directly suppress flowering in clematis.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising clematis — frequently asked questions
What fertiliser does clematis need?
Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency. Clematis flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.
How often should I feed clematis?
Clematis in fertile ground soil need little feeding; an annual spring mulch of a 5-7.5cm (2-3in) layer of organic matter is usually enough. The RHS recommends feeding container-grown clematis throughout spring and summer with an organic-based, general-purpose liquid fertiliser. Avoid high-nitrogen feeds, which encourage leaf at the expense of flowers. Clematis in fertile ground soil need little feeding; an annual spring mulch of a 5-7.5cm (2-3in) layer of organic matter is usually enough. The RHS recommends feeding container-grown clematis throughout spring and summer with an organic-based, general-purpose liquid fertiliser. Avoid high-nitrogen feeds, which encourage leaf at the expense of flowers. In practice: no routine feeding at all for clematis — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.
What strength of feed for clematis?
None is the correct answer for clematis. The flower-versus-foliage trade-off is the whole point: hold back and you get the display.
What does over-feeding clematis look like?
Abundant leafy growth and very few flowers (the classic over-rich symptom). Soft, floppy stems and a sprawling, leafy habit. Scorched edges and salt crust if it has been fed in a container. Feeding clematis at all — especially "to help it flower" — is the defining mistake. Rich soil gives you a big green plant and almost no blooms; restraint is what produces the flowers.
Should I flush the soil of clematis?
If clematis has accidentally been fed and is all leaf, a plain-water flush plus a move to leaner soil resets it; otherwise no flushing is needed because you are not feeding it.
Keep reading
- Clematis care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water clematis — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise peace lily
- How to fertilise bird of paradise
- How to fertilise hoya
- All 271 fertilising guides in the Growli library