Fertilising guide

How to fertilise Crocus sativus (Crocus sativus)— schedule & NPK

Also called saffron crocus, autumn crocus, saffron.

More about crocus sativus

About Crocus sativus

Crocus sativus · also called saffron crocus, autumn crocus · edible

Crocus sativus is the saffron crocus, a sterile autumn-flowering corm grown for its three long crimson stigmas — the world's costliest spice. Lilac-purple flowers open in October above grassy leaves. It demands full sun, hot dry summers and very sharp drainage. Plant corms 10-15 cm deep in late summer; harvest stigmas by hand at dawn on flowering days.

Growth habit: Autumn-flowering geophyte from a corm: lilac flowers emerge first, followed by long grassy leaves that persist into spring before summer dormancy. Sterile (no viable seed); multiplies steadily by offset cormlets.

What fertiliser crocus sativus actually wants — and why

Crocus sativus feeds for next year, not this one — the critical window is after flowering, while the leaves are still green and recharging the bulb.

A low-nitrogen, potassium- and phosphorus-leaning bulb fertiliser (something like 5-10-10) or bonemeal at planting. High nitrogen grows floppy leaves and rots stored bulbs.

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 crocus sativus: 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 crocus sativus, 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 crocus sativus:

Feed lightly with a low-nitrogen, potassium-rich fertiliser in autumn as growth begins and after flowering to build the corm. Excess nitrogen favours leaves over flowers; well-rotted compost or bonemeal at planting supports establishment. The rhythm: a bulb feed at planting, a light feed as leaves emerge, and — most important — a potassium feed straight after flowering while the foliage is still green and feeding the bulb. Never cut the leaves off early.

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

Use the bulb-feed label rate for crocus sativus; the timing (post-bloom, leaves still green) does far more for next year's display than the concentration.

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

Signs you are over-feeding crocus sativus

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

Tall, floppy, soft leaves that flop over (too much nitrogen).
Soft or rotting bulbs lifted at the end of the season.
Lush foliage but few or poor flowers.

Signs you are under-feeding crocus sativus

Progressively fewer or smaller flowers year on year ("going blind").
Small, weak bulbs and thin foliage.
Bulbs that fail to come back at all after a few seasons.

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

Flushing and leaching the salts

Bulbs are not container-flushed like houseplants; the equivalent is not over-feeding and lifting/dividing congested clumps of crocus sativus every few years so they are not competing for nutrients.

Organic vs synthetic feeds for crocus sativus

Organic options

Bonemeal worked in at planting plus a mulch of garden compost or well-rotted leaf-mould is the traditional, reliable approach for crocus sativus. UK: blood, fish & bone or Westland Bulb Food; US: Espoma Bulb-tone or bonemeal.

Synthetic / liquid feeds

A proprietary bulb fertiliser at planting and a high-potash liquid (tomato feed) after flowering — UK: Westland Bulb Food then Tomorite; US: Miracle-Gro Shake 'n Feed Bulb or a bloom booster post-flower.

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 crocus sativus — frequently asked questions

What fertiliser does crocus sativus need?

A low-nitrogen, potassium- and phosphorus-leaning bulb fertiliser (something like 5-10-10) or bonemeal at planting. High nitrogen grows floppy leaves and rots stored bulbs. Crocus sativus feeds for next year, not this one — the critical window is after flowering, while the leaves are still green and recharging the bulb.

How often should I feed crocus sativus?

Feed lightly with a low-nitrogen, potassium-rich fertiliser in autumn as growth begins and after flowering to build the corm. Excess nitrogen favours leaves over flowers; well-rotted compost or bonemeal at planting supports establishment. Feed lightly with a low-nitrogen, potassium-rich fertiliser in autumn as growth begins and after flowering to build the corm. Excess nitrogen favours leaves over flowers; well-rotted compost or bonemeal at planting supports establishment. The rhythm: a bulb feed at planting, a light feed as leaves emerge, and — most important — a potassium feed straight after flowering while the foliage is still green and feeding the bulb. Never cut the leaves off early.

What strength of feed for crocus sativus?