Crocus produces small, goblet-shaped flowers that open in autumn, winter, or spring to reveal inner petals in contrasting colors. Crocus is a clump-forming perennial that grow from corms. Leaves are erect and lance-shaped. In autumn species, the flowers appear before the leaves.
Crocus is a genus of hardy cormous or bulbous plant members of the Iris family. Crocus comprises many species. Seasonally, crocuses are divided into two main groups–those that bloom in the fall and those that bloom in the spring.
This article is about spring-blooming crocuses; a separate article is about Autumn Crocus.
Because of their brilliant coloring in the very early spring before most other flowers appear, the spring crocuses are extremely popular. the best effects are obtained when they are massed but informally planting of individual colors may also be had in front of shrubs or evergreens, on the edge of perennial borders, or scatted through grass that can be left unmowed for several weeks.
If the foliage is left uncut to die down naturally, the corms will increase from year to year and continue to bloom profusely until they become crowded they can be dug up and replanted while dormant in midsummer.
Corms of spring-flowering crocuses should be planted by mid-autumn spaced about 3 inches apart and set about 3 inches deep.
Crocus flower colors range from pure yellow through the various lavender and blue shades to pure white.
Get to Know Crocus
- Plant type: Hardy bulbs
- Growing Zones and range: Zones 5 to 9, farther north with shelter
- Hardiness: Most types will survive temperatures to -10°F; tolerant of heat; crocus need chilling in winter to provoke blossoming
- Height and width: 3 to 9 inches (7.6-22cm) tall and wide
- Flowers: Flowers are yellow, white, lavender, purple, violet-blue, or pink; some flowers are striped or have contrasting colors on each side of petals
- Bloom time: Bloom autumn, late winter, or early spring-blooming (before narcissus) depending on the variety
- Uses: Plant in drifts in mixed borders, rock gardens, or naturalize in short grass
- Common name: Crocus
- Botanical name: Crocus spp.
- Family: Iridaceae
- Origin: Coastal and subalpine areas of Central and South Europe, North Africa, Central Asia, Western China
Where to Plant Crocus
- Plant crocus in full sun or light shade.
- Grow crocus in humus-rich, well-drained soil.
- Crocus prefers a soil pH of 6.5 to 7.5
When to Plant Crocus
- Plant crocus in mid-fall in Zones 3-6; plant in late fall in Zones 7-8.
- Plant seeds indoors in spring.
- Plant seed outdoors in late spring.
- Plant corms of spring-blooming crocus outdoors in fall; plant fall-blooming species in summer.
- Spring bloomers may be forced in pots set in cold frames in autumn then brought indoors in winter.
Planting and Spacing Crocus
- Sow seed indoors 1/8 inch deep in small pots or flats. Grow in temperatures from 55° to 75°F (12.8°-24°C); crocus germinates in about a month but takes two or three years to bloom when grown from seed.
- Sow seed outdoors in finely tilled soil.
- Plant corms 3 inches (7.5cm) deep.
- Space crocus 3 to 6 inches (7.5-15cm) or more apart depending on the variety.
How to Water and Feed Crocus
- Crocus needs moderate water; keep the soil evenly moist.
- Water during active growth in spring and after planting in summer or fall.
- Fertilize crocus at planting time with a bulb food; fertilizer after blooms fade to nourish next year’s growth and blooms–use a bulb food high in phosphorus.
- Place an inch or two of mulch over corms for winter protection in Zones 3-6.
- Remove winter mulch in stages in late when and spring when sprouts appear.
- Remove flower heads and stems after flowers fade unless you want to collect seed.
- Let leaves die back naturally; remove them when they are yellow or brown. Mark the spot on a garden map so you know where plants will reappear next year.
Growing Crocus as a Houseplant
- Crocus requires a cold treatment before it will flower; purchase prechilled flowers or refrigerate them for a month before planting
- Grow Crocus in an all-purpose =, well-drained growing medium; do not fertilize.
- After chilling, potted plants should be placed in bright light in a cool room with average humidity.
- Keep plant evenly moist.
- Crocus will bloom in about two weeks.
- After flowers have faded, the bulbs can be discarded; they will not rebloom indoors.
Crocus Common Problems
- Mice, voles, and squirrels may feed on crocus corms.
- Deer may eat crocus blossoms; interplant crocus with narcissus which is toxic and repels deer.
- Birds sometimes pick off flowers.
- Corms in storage are susceptible to rot.
- Divide crocus every two years or when clumps become crowded; divide clumps when foliage begins to yellow following bloom time.
- Tease tangled roots and corms apart; do not cut through corns with a knife or spade.
- Replant corms and cormels after division.
- To propagate crocus from seed see above.
Crocus Varieties to Grow
- Crocus ancyrensis, golden bunch crocus. Blooms late winter to early spring; bright yellow to orange-yellow flowers marked with maroon-brown on the outside.
- C. angustifolius, cloth-of-gold crocus. Blooms mid-winter to mid-spring; orange-gold, star-like flowers with dark brown center stripe.
- C. biflorus, Scotch crocus. Blooms early spring; white or lilac=blue flowers with yellow throats; several cultivars in other colors.
- C. cartwrightianus, fall crocus. Blooms fall- to early-winter; fragrant lilac to white flowers with brilliant orange styles.
- C. chryanthus, snow crocus. Blooms in spring; orange-yellow, sweet-scented blooms; a range of hybrids in many colors.
- C. etruscus. Blooms late-winter to early-spring; lilac flowers with yellow throats.
- C. flavus. Blooms in spring; orange-yellow flowers.
- C. goulimyi, fall crocus. Blooms fall; rosy lilac flowers.
- C. imperati, Italian crocus. Blooms early spring; bright lilac inside, buff veined purple outside.
- C. korolkowii, Celandine crocus. Blooms late-winter to early-spring; golden yellow flowers feathered with brown on the outside.
- C. kotschyanus. Blooms early fall; pinkish lavender or lilac flowers.
- C. laevigatus. Blooms fall- to early-winter; white or lilac flowers are yellow-tan on the outside and streaked with violet-purple.
- C. longiflourus. Blooms fall; fragrant pale to dark lilac flowers.
- C. medius. Blooms fall; pale to dark purple flowers with brilliant orange styles.
- C. minimus. Blooms late spring; lilac-purple flowers and yellow-buff outer petals marked in dark purple.
- C. niveus. Blooms in fall; white or pale lilac flowers with orange styles.
- C. ochroleucus. Blooms fall; creamy white flowers with yellow throats.
- C. pulchellus. Blooms fall to early winter; pale lilac-blue flowers with yellow throats.
- C. sativus, saffron crocus. Autumn bloom; orange-red stigma is true saffron; to harvest saffron, pluck the stigmas as soon as the flower opens, dry them, and store them in a glass jar.
- C. sieberi. Early spring bloom; delicate lavender-blue flower with golden throat.
- C. speciosus, fall crocus. Blooms early fall; showy blue-violet flowers; showiest autumn-flowering crocus.
- C. tommasinianus. Blooms mid- to late winter; star-shaped, silvery lavender-blue flowers, sometimes with dark blotch tips.
- C. vernus, Dutch crocus. Blooms late winter to mid-spring; most vigorous and most widely sold; shades of white, yellow, lavender, and purple.
- C. versicolor.