How to grow crocuses

What are crocuses?

Crocus are very dwarf perennials

Perennials are plants that live for multiple years. They come in all shapes and sizes and fill our gardens with colourful flowers and ornamental foliage. Many are hardy and can survive outdoors all year round, while less hardy types need protection over winter. The term herbaceous perennial is used to describe long-lived plants without a permanent woody structure (they die back to ground level each autumn), distinguishing them from trees, shrubs and sub-shrubs. growing from an underground corm

A corm is a bulb-like, underground swollen plant stem or stem base, usually surrounded by papery skin (tunic). See crocus, crocosmia and gladiolus. . Their deciduous

Deciduous refers to plants (mainly trees and shrubs) that lose their leaves seasonally, usually during autumn. This is a natural process triggered by the season's shorter days and lower temperatures and allows plants to conserve energy during the winter months. , linear leaves usually have a silvery central stripe. The goblet-shaped, sometimes fragrant, flowers bloom in early spring or autumn.

Choosing crocuses for your garden

Decide what season you want crocuses for and where you want to grow them. Here are some ideas:

Crocuses for spring

For naturalising in sparse grass and under deciduous trees: Try the slender pale lilac C. tommasinianus cultivars. They offer early flowers in February to March.

For rock gardens and soils that are dry in summer but have similar sun/part-shade conditions to deciduous trees: Try C. chysanthus cultivars for March flowering.

For naturalising in lawns: Try the C. vernus hybrids. They're referred to as Dutch hybrids and have quite stout goblet flowers in March. Examples include C. 'Pickwick' and C. 'Flower Record'.

For containers in March: Try the wide choice of cultivars including C. 'Snow Bunting' and C. x luteus 'Golden Yellow' and again the Dutch hybrids like C. 'Vanguard'.

Crocuses for autumn

For naturalising in short, sparse grass: Try C. speciosus cultivars

For alpine houses and cold frames: Try the Crocus species that aren't at home with conditions generally provided by the UK’s maritime climate, so are best grown with some protection. Examples include C. niveus and C. boryi. They're summer dormant

Dormancy refers to a period of inactivity in plants, during which they slow down or stop their growth, conserving energy and resources. This is a natural process that helps them survive harsh conditions, such as winter or drought. Dormancy in seeds is a mechanism that prevents them germinating until environmental conditions are favourable for growth. and want a dry baking, so protect from summer rain in an alpine house or cold frame

Cold frames are glaze box-like structures made from brick or wood with a  hinged or removable, glazed, sloping lid. Useful to protect plants from cold weather over winter or acclimatise (harden off) young plants in spring and provide extra warmth for tender crops in summer. . They are happy with some winter moisture and cold temperatures.

For well-draining garden sites, rock gardens and raised beds: Try a group of species that are less picky than the alpine house types and that can be grown outdoors with a bit of soil preparation. This group tolerates summer moisture as long as the drainage is right. Examples include C. sativus and C. etruscus.

For more selection details see: 'Choosing Crocus by flowering season'

Where and when to buy

Spring flowering crocuses
These are sold and planted in autumn as dry corms. Garden centres also sell them in growth in early spring in containers as flowering plants.

Autumn flowering crocuses
These are for sale in late summer in the garden centre and from bulb nurseries via mail order. They're planted a little bit earlier (in September) than other garden bullbs like daffodils, tulips and spring flowering crocuses.

Spring flowering crocus - when to plant

Plant spring flowering crocuses during the autumn.

Spring flowering crocus - where to plant

Naturalised

Naturalised plants are those that have been introduced to a place outside of their native range and have become established in the wild there, surviving, reproducing and spreading without help. Sycamores, snowdrops and sweet chestnuts are naturalised plants in the UK. C. tommasinianus cultivars and C. chysanthus cultivars look best in swathes of small groups in sparse, short rough grass and under deciduous

Deciduous refers to plants (mainly trees and shrubs) that lose their leaves seasonally, usually during autumn. This is a natural process triggered by the season's shorter days and lower temperatures and allows plants to conserve energy during the winter months. trees.

Dutch hybrids (C. vernus) are the top choice for planting under garden lawns and in containers.

Spring flowering crocus - how to plant

To naturalise C. tommasinianus and C. chysanthus plant 7-10cm (3-4in) deep in small groups.

In garden lawns, Dutch hybrids have bigger corms so can go a bit deeper at 12cm (5in). Space individually about 9cm (4in) apart.
For tips on making bulbs

These are fleshy, rounded, underground storage organs, usually sold and planted while dormant. Examples include daffodils, tulips, hyacinths, lilies, onions and garlic. The term is often used to cover other underground storage organs, including corms, tubers and rhizomes. look natural and planting at scale see here.

In containers, plant crocus as the top layer above other bulbs 7-12cm deep (3-45n).

Autumn flowering crocus - when to plant

These are planted in late summer, generally September, so if they flower in their first year, it may be a little later than normal. Once settled in, their flowering is triggered by the lower temperatures and higher soil moisture in autumn.

Autumn flowering crocus - where to plant

Species like C. speciosusare good for naturalising outdoors in sparse short grass in an open site.

For well-draining garden sites use species like C. sativus and C. etruscus that can be grown in many open garden situations with a bit of soil preparation. C. sativus could be grown on a well- draining allotment in a mild location if you want to try your hand at saffron harvesting.

For the more specialist crocus like C. niveus, grow in pots in an unheated greenhouse (cold glasshouse) or coldframe. With this protection they'll avoid the worst of the wet and cold when flowering and will be assured of a dry summer baking when dormant

Dormancy refers to a period of inactivity in plants, during which they slow down or stop their growth, conserving energy and resources. This is a natural process that helps them survive harsh conditions, such as winter or drought. Dormancy in seeds is a mechanism that prevents them germinating until environmental conditions are favourable for growth. .

Autumn flowering crocus - how to plant

For naturalising outdoors, plant species like C. speciosusat 12cm (5in) deep.

For species like C. sativus and C. etruscus that are less picky than the alpine house types because they’ll tolerates summer moisture, just make sure that the drainage is right. Dig in leafmould and sharp grit into the top 20cm (8in) of soil and plant on a layer of sharp sand

Sharp sand is washed, gritty sand used in potting compost mixes, This is sold for gardening and is not the same as builders sharp sand. , maybe in a rock garden, alpine trough or raised bed.

For alpine house (cold glasshouse) specialist crocuses like C. niveus, plant in pots around 10-13cm (4-5in) deep in a gritty peat-free, loam-based growing medium.

Watering

Watering isn't usually required for outdoor crocuses except in perhaps in containers. When in leaf, check with your finger that the growing medium (potting compost

Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own. ) feels moist to the touch a few inches down.
For specialist crocuses in the greenhouse, watering will be based on the rainfall patterns of their orginal habitat.

Feeding

Crocuses grown in the ground shouldn't need feeding.

Specialist crocuses grown in containers can be fed with a high potassium liquid feed when in leaf, making sure to follow the dose rate and frequency recommended by the manufacturer.

Aftercare

Allow the foliage of crocuses to die back naturally rather than removing it when it's still green. There's no need to deadhead

Deadheading is the process of removing spent flowers from plants to encourage more blooms and prevent seed production. This helps to redirect the plant's energy into producing more flowers rather than producing seeds. .

For crocuses planted in grass, hold off mowing until the foliage dies back to aid perennialisation.

Dig up crocuses from spring containers after the foliage dies down. Store in paper bags somewhere cool and dry until replanting in autumn.

Specialist crocuses grown in containers can be repotted every other year using a free-draining, loam-based potting mix.

Crocus are generally left to multiply by themselves if naturalised

Naturalised plants are those that have been introduced to a place outside of their native range and have become established in the wild there, surviving, reproducing and spreading without help. Sycamores, snowdrops and sweet chestnuts are naturalised plants in the UK. - by seed or mini corms. Many in general display containers are treated as disposable but can be replanted into the garden after flowering.

Propagating by division

You can divide established groups of both spring and autumn flowering crocus in late summer and replant. However some like C. tommasinianusflower best when congested.

Propagating by cormels

If you want to increase your stocks, grow on the little cormels that grow around older corms or from underground stems. Line these cormels out in drills in the garden or in pots until they bulk up to flowering size. (If you want to actively promote cormel formation, plant your stock crocus corms shallowly)

Propagating by seed

Sow home-harvested seed when ripe The seed capsule for spring flowering types should appear from below ground in early to mid summer.
Collect seed before the capsule splits. Sow in a pot of well-draining, peat-free seed compost

Seed compost is a free-draining compost formulated for germinating seed. It often contains a mix of fine materials including sterilised loam, coir, coarse sand or grit. It contains low levels of nutrients, as high levels could damage seedlings. and allow to grow on for two years - the protection of a cold frame

Cold frames are glaze box-like structures made from brick or wood with a  hinged or removable, glazed, sloping lid. Useful to protect plants from cold weather over winter or acclimatise (harden off) young plants in spring and provide extra warmth for tender crops in summer. would be ideal. Pot on to give the small plants more space as the foliage dies down at the end of their second season. Seedlings

A seedling is a young plant grown from seed. need to be watered well through the year. Plants should flower in their third or fourth year
For more tips on propagating bulbs

These are fleshy, rounded, underground storage organs, usually sold and planted while dormant. Examples include daffodils, tulips, hyacinths, lilies, onions and garlic. The term is often used to cover other underground storage organs, including corms, tubers and rhizomes. , see here.

Watch out for bird, squirrel and rodent damage. Planting under a metal mesh may reduce losses.

Store in cool dry conditions to avoid the fungal rots that bulbs

These are fleshy, rounded, underground storage organs, usually sold and planted while dormant. Examples include daffodils, tulips, hyacinths, lilies, onions and garlic. The term is often used to cover other underground storage organs, including corms, tubers and rhizomes. and corms can suffer from.
Physical damage gives pathogens another opportunity to attack corms, so handle them with care.
See bulb storage tips here.