Autumn Crocus (Colchicum autumnale)

How much light does an Autumn Crocus need?

This plant's light needs run from full sun to part shade, with full sun listed as the preferred option. Full sun means six hours or more of direct sunlight each day, the brighter end of the range this plant will accept. Part shade also works outdoors, though full sun remains the stronger choice.

• Light: Full sun and part shade (full sun preferred)^1,2,3

How often to water an Autumn Crocus

This plant's water need is listed as medium, meaning it should get a regular supply without heavy watering or drought-level dryness. That medium level comes from its preference for well-drained soil that doesn't dry out in summer. The soil itself should be well drained and moist.

• Water: Medium⁴

Best soil for an Autumn Crocus

This plant grows best in rich, well-drained loam that still holds some moisture rather than drying out completely. Soil pH matters too: this plant tolerates a fairly wide range, from 4.5 up to 7.5. That pH window runs from somewhat acidic at 4.5 to mildly alkaline at 7.5. Its soil should also stay moist enough that it doesn't dry out completely during summer, in addition to draining well.

• Soil drainage: Well drained and moist^1,4,2,4
• Soil pH: pH 4.5–7.5¹

Hardiness and temperature

This plant grows outdoors in USDA hardiness zones 4a through 9b. In the coldest parts of that range, this plant can survive winter temperatures down to about -4°F (-20°C). Zone 9b marks the warmer end of its hardiness range, while zone 4a marks the colder end of that span. That span covers twelve numbered half-zones in total, from the lowest, 4a, up through the highest, 9b.

• Hardiness: Zones 4a–9b¹
• Minimum temperature: -4 °F (-20 °C)¹

How to plant an Autumn Crocus

This plant grows well outdoors in USDA hardiness zones 4a through 9b. At maturity it stands about 0.5 to 1.2 ft (0.15-0.36 m) tall, with a spread of roughly 0.5 to 0.7 ft (0.15-0.2 m). When planting, space new plants about that same distance apart. This plant grows from a bulb. In the lower 48 US states, this plant's status is listed as introduced.

• Hardiness: Zones 4a–9b¹

Winter care

This plant is hardy outdoors through USDA zone 4a, the coldest zone in its range. In that zone and the others up to 9b, it can tolerate winter temperatures down to about -4°F (-20°C). Gardeners in colder zones than 4a fall outside the range this cold tolerance covers. That same -4°F (-20°C) figure is the lowest winter temperature this plant can survive outdoors.

• Hardiness: Zones 4a–9b¹
• Minimum temperature: -4 °F (-20 °C)¹

How to propagate an Autumn Crocus

You can propagate this plant from seed, or you can increase your stock of it through division. Divide the plants in summer, after the leaves have died back, if you want to move or split them. Growing new plants from seed is the other option available to gardeners who prefer not to divide established clumps.

• Propagation: Seed and division^1,4

Common problems

Slugs are a common pest, and they may attack the corms of this plant. The stem and bulb nematode, Ditylenchus dipsaci, is another pest recorded on this plant. Fungal smut can affect the leaves as well. This plant is also reported to resist drought, rabbits, and deer.

• Common pests: slugs and stem and bulb nematode^1,5
• Common diseases: smut¹

Questions and answers

Is this plant toxic to cats and dogs?

This plant is toxic to both cats and dogs. It poses a particular threat specifically to cats. Dogs are also listed separately as being at risk from this plant.

How much sun does this plant need?

This plant does best in full sun, which means six or more hours of direct sunlight a day. It also tolerates part shade, though full sun remains its stronger preference.

What hardiness zones can this plant grow in?

This plant grows outdoors in USDA hardiness zones 4a through 9b. In the coldest of those zones, it can survive winter temperatures down to about -4°F (-20°C).