Fertilising guide

How to fertilise Tansy (Tanacetum vulgare)— schedule & NPK

Also called tansy, common tansy, bitter buttons.

More about tansy

About Tansy

Tanacetum vulgare · also called tansy, common tansy · herb

Tansy (Tanacetum vulgare) is a tough, aromatic perennial with fern-like foliage and flat clusters of button-yellow flowers in mid to late summer. Pungent and vigorous, it tolerates poor soil and drought, spreads strongly by rhizome, and is classed as an invasive weed in parts of North America. Long grown as an insect-repellent and dye herb.

Growth habit: Erect, rhizomatous herbaceous perennial forming spreading colonies of aromatic ferny foliage topped by corymbs of yellow disc flowers; aggressively clonal and can become weedy.

Watch for — Flopping in rich soil: Tall stems sprawl in fertile ground or shade; grow hard in lean soil and full sun, or cut back by half in early summer for sturdier regrowth.

What fertiliser tansy actually wants — and why

Tansy is a soft, fast leafy herb that you harvest hard — a modest balanced feed keeps tender growth coming without tipping it into bland or bolting.

A balanced general feed (even N-P-K) at modest strength — enough nitrogen to keep replacing the leaves you pick, but not so much that flavour thins or it bolts to seed.

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 tansy: 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 tansy, 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 tansy:

Needs little to no feeding; it grows lush in poor ground. Skip nitrogen-rich feeds, which worsen flopping and spread. A light spring compost mulch is more than sufficient. In practice: a balanced liquid feed every few weeks through the main growing and harvesting season (spring through early autumn), more often the harder you are picking it.

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

Half strength is a sensible default for tansy — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.

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

Signs you are over-feeding tansy

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

Fast, soft, pale growth with diluted, less aromatic flavour.
Early bolting (running to flower) and a bitter edge.
Salt crust and scorched tips on container plants.

Signs you are under-feeding tansy

Pale, slow regrowth after cutting and small leaves.
A tired, stalled plant that cannot keep up with harvesting.
Yellowing older leaves in a long-spent pot.

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

Flushing and leaching the salts

Pot-grown tansy builds up feed salts quickly — water until it drains each time and flush the pot with plain water every few weeks, especially on a sunny windowsill.

Organic vs synthetic feeds for tansy

Organic options

A diluted seaweed feed or worm-casting tea keeps soft growth coming without overdoing it. UK: dilute seaweed or Westland; US: Espoma Garden-tone or Neptune's Harvest. Gentle, hard to overdo, flavour-friendly.

Synthetic / liquid feeds

A balanced liquid feed at half strength through harvesting — UK: Phostrogen, Baby Bio or Westland; US: Miracle-Gro all-purpose at half strength. Fast regrowth; just do not overdo the nitrogen.

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 tansy — frequently asked questions

What fertiliser does tansy need?

A balanced general feed (even N-P-K) at modest strength — enough nitrogen to keep replacing the leaves you pick, but not so much that flavour thins or it bolts to seed. Tansy is a soft, fast leafy herb that you harvest hard — a modest balanced feed keeps tender growth coming without tipping it into bland or bolting.

How often should I feed tansy?

Needs little to no feeding; it grows lush in poor ground. Skip nitrogen-rich feeds, which worsen flopping and spread. A light spring compost mulch is more than sufficient. Needs little to no feeding; it grows lush in poor ground. Skip nitrogen-rich feeds, which worsen flopping and spread. A light spring compost mulch is more than sufficient. In practice: a balanced liquid feed every few weeks through the main growing and harvesting season (spring through early autumn), more often the harder you are picking it.

What strength of feed for tansy?