Fertilising guide

How to fertilise Calendula (Calendula officinalis)— schedule & NPK

Also called pot marigold, common marigold, English marigold, Scotch marigold, garden marigold.

More about calendula

About Calendula

Calendula officinalis · also called pot marigold, common marigold · flowering

Calendula (pot marigold) is a fast-growing cool-season annual prized for vivid orange and yellow daisy-like blooms that flower from late spring until the first hard frost. Easy from seed, it thrives in full sun and free-draining soil, and its edible petals are a kitchen favourite. Pet-safe — the ASPCA lists it as non-toxic to cats and dogs.

Growth habit: Fast-growing bushy annual

What fertiliser calendula actually wants — and why

Calendula 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 calendula: 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 calendula, 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 calendula:

A light feeder. Work a little compost into the bed at planting; an occasional balanced feed is plenty. Avoid high-nitrogen feeds, which give leaves at the expense of flowers. In practice: no routine feeding at all for calendula — 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 calendula 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 calendula

None is the correct answer for calendula. 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 calendula first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the calendula watering schedule.

Signs you are over-feeding calendula

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

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 calendula

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 calendula care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

If calendula 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 calendula

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 calendula.

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 calendula — frequently asked questions

What fertiliser does calendula 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. Calendula 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 calendula?

A light feeder. Work a little compost into the bed at planting; an occasional balanced feed is plenty. Avoid high-nitrogen feeds, which give leaves at the expense of flowers. A light feeder. Work a little compost into the bed at planting; an occasional balanced feed is plenty. Avoid high-nitrogen feeds, which give leaves at the expense of flowers. In practice: no routine feeding at all for calendula — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.

What strength of feed for calendula?