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Fertilising guide

How to fertilise Garden Catmint (Nepeta x faassenii)— schedule & NPK

Also called garden catmint, Faassen's catmint.

More about garden catmint

About Garden Catmint

Nepeta x faassenii · also called garden catmint, Faassen's catmint · flowering

Garden catmint is a sterile, clump-forming perennial prized for soft grey-green aromatic foliage and long sprays of lavender-blue flowers from late spring into autumn. A magnet for bees and butterflies, it thrives in poor, free-draining soil and full sun, shrugging off heat and drought. Shearing spent flowers triggers a fresh, tidy second flush.

Growth habit: Low, spreading mound of branching aromatic stems forming a soft, billowing dome that spills gracefully over path edges and borders.

What fertiliser garden catmint actually wants — and why

Garden Catmint is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.

A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula.

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 garden catmint: 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 garden catmint, 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 garden catmint:

Very light feeders. A single spring application of balanced general fertiliser or a thin mulch of compost is ample. Over-feeding causes lush, weak growth that flops and flowers poorly. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.

The dormant-season rule matters more than the exact interval: skip feeding entirely when garden catmint 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 garden catmint

Half strength is the safe default for garden catmint — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.

Feeding always goes onto already-damp soil, never dry roots — water garden catmint first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the garden catmint watering schedule.

Signs you are over-feeding garden catmint

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for garden catmint:

Signs you are under-feeding garden catmint

If the symptoms point at watering, light or roots rather than nutrition, the full garden catmint care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Flush the pot of garden catmint with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.

Organic vs synthetic feeds for garden catmint

Organic options

A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.

Synthetic / liquid feeds

A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.

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 garden catmint — frequently asked questions

What fertiliser does garden catmint need?

A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Garden Catmint is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.

How often should I feed garden catmint?

Very light feeders. A single spring application of balanced general fertiliser or a thin mulch of compost is ample. Over-feeding causes lush, weak growth that flops and flowers poorly. Very light feeders. A single spring application of balanced general fertiliser or a thin mulch of compost is ample. Over-feeding causes lush, weak growth that flops and flowers poorly. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.

What strength of feed for garden catmint?

Half strength is the safe default for garden catmint — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.

What does over-feeding garden catmint look like?

Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding garden catmint year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.

Should I flush the soil of garden catmint?

Flush the pot of garden catmint with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.

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