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Crocus 'Ruby Giant'

Crocus tommasinianus 'Ruby Giant' · Iridaceae

Crocus 'Ruby Giant' (Crocus tommasinianus 'Ruby Giant') in flower
Photo: Meneerke bloem, via Wikimedia Commons (CC BY-SA 3.0)

Slender flowers of rich red-purple that open flat in the sun, among the very first crocuses of the year.

Size
4 in tall, 3 in wide
Zones
3 to 8
Light
Full sun to part sun
Flowers
Early March to late March
Pets
Toxic (mild)
Job in a bed
Bulb layer

A bed built around crocus 'Ruby Giant'

The planner designed this bed around crocus 'Ruby Giant' when this page was made: a 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why crocus 'Ruby Giant' stands where it does.

A 12 × 6 ft (3.7 × 1.8 m) bed at eye level in late March: Bloody cranesbill 'Max Frei', Leadwort, False sunflower 'Summer Sun', Tatarian aster 'Jindai', Arborvitae 'Mr. Bowling Ball', Bergenia 'Bressingham White', Crocus 'Ruby Giant', Star of Persia.
A 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, full sun, seen from the path in late March.
4. Tatarian aster 'Jindai'44. Tatarian aster 'Jindai'44. Tatarian aster 'Jindai'43. False sunflower 'Summer Sun'33. False sunflower 'Summer Sun'33. False sunflower 'Summer Sun'35. Arborvitae 'Mr. Bowling Ball'51. Bloody cranesbill 'Max Frei'11. Bloody cranesbill 'Max Frei'11. Bloody cranesbill 'Max Frei'11. Bloody cranesbill 'Max Frei'11. Bloody cranesbill 'Max Frei'12. Leadwort22. Leadwort22. Leadwort22. Leadwort22. Leadwort21. Bloody cranesbill 'Max Frei'11. Bloody cranesbill 'Max Frei'11. Bloody cranesbill 'Max Frei'18. Star of Persia88. Star of Persia86. Bergenia 'Bressingham White'66. Bergenia 'Bressingham White'66. Bergenia 'Bressingham White'62. Leadwort22. Leadwort22. Leadwort28. Star of Persia88. Star of Persia87. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'7. Crocus 'Ruby Giant'
From above, to scale. Each circle is one plant, as wide as the room it needs.

The plants

  1. 1 Bloody cranesbill 'Max Frei' × 8, pink
  2. 2 Leadwort × 8, blue
  3. 3 False sunflower 'Summer Sun' × 3, yellow
  4. 4 Tatarian aster 'Jindai' × 3, purple
  5. 5 Arborvitae 'Mr. Bowling Ball' × 1, grey-green leaves
  6. 6 Bergenia 'Bressingham White' × 3, white
  7. 8 Star of Persia × 4, purple

Why this plant

  • Nothing here is unique to it. Its leaf, flower shape and colour are all on the plan already. Its case rests on where it stands and when it performs.

Why here

  • Near the front. At 4 in it stands ahead of bergenia 'Bressingham White' (14 in) without hiding it.
  • 12 plants in 2 handfuls. In the gaps between other plants, which fill the space when the bulb is not in growth.

Why now

  • In flower for four weeks. From early March to late March.
  • Opens the season. In all that time nothing else on the plan is in flower.
  • Leaves gone by midsummer. They die back and leave bare ground. A perennial that comes up late stands beside it, and grows over the gap.

Planned as an English border: 6 of the 6 groups (100%) are drifts, longer along the bed than they are deep. The back corners are held by false sunflower 'Summer Sun' and Tatarian aster 'Jindai', the tallest plants on the plan. It is planted in layers: about 8 in at the front, 24 in in the middle and 3½ ft at the back.

The planner's own design check: 11 Excellent, 6 Good. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.

Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.

Where crocus 'Ruby Giant' goes in a border

At 4 in it belongs at the front of a bed. In the planner's ten height classes it is ground-hugging (up to 6 in).

Its job: bulb layer. Small bulbs planted in handfuls of five or seven in the gaps between other plants, for colour before the perennials wake up.

The crocus that squirrels leave alone. It multiplies quickly and is the best kind for naturalising in a lawn: the leaves have died down before the first mowing.

  • Naturalising in lawns
  • The first colour of spring
  • Under deciduous trees

What to plant with crocus 'Ruby Giant'

Plants recorded as good partners for it, and what each pairing does:

  • Snowdrop: in flower together for four weeks, from early March.
  • Winter aconite: purple against yellow, opposite each other on the colour wheel, in flower together for two weeks.
  • Siberian squill.

Questions about crocus 'Ruby Giant'

Does crocus 'Ruby Giant' need sun or shade?

Crocus 'Ruby Giant' grows in full sun (6 or more hours of direct sun a day) and part sun (4 to 6 hours of sun, including some afternoon sun).

It wants ordinary well-drained soil, of average fertility, and little watering once settled.

What zones does crocus 'Ruby Giant' grow in?

USDA zones 3 to 8. It is hardy to zone 3, which means it survives winter nights down to about −30 °F (−34 °C).

Above zone 8 it struggles: the zones measure winter cold, but a plant's top zone usually means the summers are too hot or the winters too mild for it to rest.

Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.

When does crocus 'Ruby Giant' flower in my zone?

In zone 5 it flowers early March to late March. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.

Roughly when crocus 'Ruby Giant' is in flower
Zone 3Late March to mid April
Zone 4Mid March to early April
Zone 5Early March to late March
Zone 6Early March to late March
Zone 7Late February to mid March
Zone 8Mid February to early March

Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.

How far apart should crocus 'Ruby Giant' be planted?

3 in (8 cm) apart, from the middle of one plant to the middle of the next. That is about its full width, so each plant keeps its own outline.

It grows 4 in (10 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.

How many crocus 'Ruby Giant' plants do I need?

At 3 in apart, set out in staggered rows:

  • 168 to fill 10 square feet (about 1 m²)
  • 39 for a single row 10 ft (3 m) long
  • 536 to fill a 4 × 8 ft bed on its own

In a mixed border, plant it as handfuls of five or seven, in the gaps between other plants.

In the bed above, the planner used 12 in two groups.

Is crocus 'Ruby Giant' poisonous to dogs and cats?

Yes: mild toxicity to dogs and cats. May cause mild stomach upset if eaten. This is a true crocus, not the highly poisonous meadow saffron (Colchicum).

Rated from NC State Extension. Where references disagree, the more cautious rating is used.

Is there a pet-safe plant like crocus 'Ruby Giant'?

These come closest to doing what crocus 'Ruby Giant' does, and no toxicity is recorded for them:

  • Spring starflower: the same job in a bed and the same size; flowers early April to early May, blue or white, not purple.
  • Striped squill: the same job in a bed and the same size; flowers late March to mid April, blue, not purple.

Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.

Do deer eat crocus 'Ruby Giant'?

Mostly not. NC State lists it as resistant to deer. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.

What can I plant to hide crocus 'Ruby Giant''s leaves after it flowers?

A bulb's leaves have to be left to yellow for about six weeks after flowering, to feed next year's flowers. Plant it among perennials that come up late and spread wide, and they grow over the leaves as they fade:

What does crocus 'Ruby Giant' look like in winter?

Crocus 'Ruby Giant' is underground: it dies back after flowering and waits as a bulb until spring. Mark where it is, so a fork does not find it first.

More Crocus

In these guides

Zone guides: Zone 3 · Zone 4 · Zone 5 · Zone 6 · Zone 7 · Zone 8

In flower in: March

Every fact on record

Type
Bulb
Size
4 in (10 cm) tall, 3 in (8 cm) wide
Plant
3 in (8 cm) apart
Height class
Ground-hugging (up to 6 in)
Place in the bed
Front
Flowers
Early March to late March; open bowls; purple
Leaves
Fine texture, summer-dormant; green
Shape
Mounding, clumping
Hardy in
USDA zones 3 to 8
Light
Full sun, part sun
Soil
Average, well-drained
Water
Low
Feeding
None needed
Family
Iridaceae
Comes from
Europe
Stands up to
Deer, black walnut

Checked against NC State Extension. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.