Fertilising guide
How to fertilise Crocus tommasinianus 'Ruby Giant' (Crocus tommasinianus 'Ruby Giant')— schedule & NPK
Also called Ruby Giant crocus, Tommie crocus, purple Tommasinianus crocus.
More about crocus tommasinianus 'ruby giant'
About Crocus tommasinianus 'Ruby Giant'
Crocus tommasinianus 'Ruby Giant' · also called Ruby Giant crocus, Tommie crocus · flowering
Crocus tommasinianus 'Ruby Giant' is an early, slender 'Tommie' crocus bearing rich reddish-purple, silvery-backed flowers in late winter to early spring. Sterile but vigorous, it spreads by offsets to naturalise quickly in lawns and gravel. Plant corms 7-10 cm deep in autumn in full sun and free-draining soil; it is famously squirrel-resistant compared with larger Dutch crocus.
Growth habit: Slender, early-flowering geophyte from a small corm with very fine grassy leaves and delicate goblet blooms. A strong, fast naturaliser spreading mainly by offsets to form extensive carpets.
What fertiliser crocus tommasinianus 'ruby giant' actually wants — and why
Crocus tommasinianus 'Ruby Giant' 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 tommasinianus 'ruby giant': 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 tommasinianus 'ruby giant', 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 tommasinianus 'ruby giant':
Very low feeder; thrives in lean soil. A light bulb feed or bonemeal at planting is ample, with an optional low-nitrogen top-dressing as growth appears in late winter. Over-feeding favours leaf over flower. 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 tommasinianus 'ruby giant' 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 tommasinianus 'ruby giant'
Use the bulb-feed label rate for crocus tommasinianus 'ruby giant'; 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 tommasinianus 'ruby giant' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the crocus tommasinianus 'ruby giant' watering schedule.
Signs you are over-feeding crocus tommasinianus 'ruby giant'
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for crocus tommasinianus 'ruby giant':
- 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 tommasinianus 'ruby giant'
- 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 tommasinianus 'ruby giant' 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 tommasinianus 'ruby giant' every few years so they are not competing for nutrients.
Organic vs synthetic feeds for crocus tommasinianus 'ruby giant'
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 tommasinianus 'ruby giant'. 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 tommasinianus 'ruby giant' — frequently asked questions
What fertiliser does crocus tommasinianus 'ruby giant' 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 tommasinianus 'Ruby Giant' 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 tommasinianus 'ruby giant'?
Very low feeder; thrives in lean soil. A light bulb feed or bonemeal at planting is ample, with an optional low-nitrogen top-dressing as growth appears in late winter. Over-feeding favours leaf over flower. Very low feeder; thrives in lean soil. A light bulb feed or bonemeal at planting is ample, with an optional low-nitrogen top-dressing as growth appears in late winter. Over-feeding favours leaf over flower. 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 tommasinianus 'ruby giant'?
Use the bulb-feed label rate for crocus tommasinianus 'ruby giant'; the timing (post-bloom, leaves still green) does far more for next year's display than the concentration.
What does over-feeding crocus tommasinianus 'ruby giant' look like?
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. Cutting or tying off the leaves of crocus tommasinianus 'ruby giant' as soon as the flowers fade is the great bulb mistake — the bulb recharges through those leaves for weeks afterward, and removing them early means a weak or blind display next year.
Should I flush the soil of crocus tommasinianus 'ruby giant'?
Bulbs are not container-flushed like houseplants; the equivalent is not over-feeding and lifting/dividing congested clumps of crocus tommasinianus 'ruby giant' every few years so they are not competing for nutrients.
Keep reading
- Crocus tommasinianus 'Ruby Giant' care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water crocus tommasinianus 'ruby giant' — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
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- All 3899 fertilising guides in the Growli library