Few flowers accomplish so much with so little. Crocuses rise only a few inches above the earth, yet when their cups of purple, gold, lavender, striped violet, and white begin opening, they can transform the appearance of an entire garden.
For many gardeners, the crocus is the first unmistakable announcement that winter is losing its grip. A patch of crocuses pushing through cold ground — sometimes even through snow — is one of those small events by which gardeners have marked the turning of the year for centuries.
Yet there is more to the genus Crocus than the familiar spring flowers. Some crocuses bloom in autumn, and one of them has been cultivated since antiquity to produce one of the world's most precious spices: saffron.
Where Are Crocuses Native?
Crocuses belong to the iris family, Iridaceae, and grow from corms, rather than true bulbs. A corm is a swollen underground stem that stores the plant's food from one season to the next.
The natural home of Crocus lies largely in the Old World, particularly around the Mediterranean and southeastern Europe and eastward into western and central Asia. Different species are native to different regions.
The familiar spring or Dutch crocus, Crocus vernus, has its origins in the Alps and western Balkans. Crocus chrysanthus, from which many of our small early-flowering yellow and bicolored varieties are derived, is native from southeastern Europe into Türkiye. Other species occur in Greece, the Balkans, Spain, North Africa, Türkiye, Lebanon and neighboring regions.
This helps explain what crocuses generally want in the garden: sunshine, cool winters, moisture while actively growing, and soil that drains freely rather than remaining waterlogged.
Crocuses Have Been Cultivated for a Very Long Time
There isn't really a single person who can be credited with "introducing" the crocus into cultivation.
Humankind's relationship with crocuses reaches back into antiquity, long before modern botanical collecting and commercial bulb growing. The most famous example is the saffron crocus, Crocus sativus, which was already being cultivated thousands of years ago.
The larger spring crocuses familiar in modern gardens were developed through centuries of European cultivation and selection. The species we now call Crocus vernus was formally described botanically in the eighteenth century, but European gardeners knew crocuses long before botanists settled their modern scientific names.
By the nineteenth century, European nurserymen and plant collectors were bringing numerous crocus species into cultivation and selecting forms for larger flowers, stronger colors and better garden performance.
Thus the crocus is both an ancient cultivated plant and a thoroughly modern garden flower.
Spring-Flowering Crocuses
These are the crocuses most gardeners know.
Depending upon climate and variety, they bloom from late winter into early spring. Some of the smaller species and hybrids appear remarkably early.
Among the best-known groups are:
- Crocus vernus and its large-flowered Dutch forms
- Crocus chrysanthus and its hybrids
- Crocus tommasinianus, often affectionately called "Tommies"
- Crocus sieberi
- Crocus angustifolius
The large Dutch crocuses make bold patches of purple, white and striped flowers. The smaller species crocuses are often more delicate but can be particularly charming when allowed to naturalize.
Don't Forget the Autumn Crocuses
Not every crocus waits for spring.
Several true Crocus species flower in autumn, including Crocus speciosus, Crocus pulchellus and the celebrated Crocus sativus. Their flowers appear when much of the garden is beginning to wind down for the year.
There is an important botanical warning here.
Plants in the genus Colchicum are also commonly called "autumn crocuses," but they are not true crocuses. This distinction is especially important because colchicums are poisonous and should never be mistaken for saffron crocus.
The Saffron Crocus
Crocus sativus deserves special mention because few garden plants have had such a remarkable history.
Saffron is produced from the three brilliant red stigmas inside each flower. They are picked by hand and carefully dried.
And that explains the price.
It takes roughly 150 flowers to produce only about one gram of dried saffron.
The saffron crocus is an ancient cultivated plant whose exact wild origin has long been debated. Modern botanical authorities regard it as a cultigen originating in Greece, and it was probably selected thousands of years ago from a related wild crocus, generally identified as Crocus cartwrightianus. Crocus sativus is sterile, so it does not reproduce by seed. Human beings have perpetuated it by dividing and replanting its corms generation after generation.
That means every saffron crocus growing today belongs to a cultivated tradition stretching far back into antiquity.
For the adventurous gardener, saffron can be grown at home. Give the corms full sun and exceptionally good drainage, plant them about 4 to 6 inches deep and roughly 4 inches apart, and expect their lavender-purple flowers in autumn.
When Should Crocuses Be Planted?
The answer depends upon when they flower.
Spring-flowering crocuses should be planted in autumn, while the corms are dormant. September through November is suitable in many climates, and planting can continue as long as the soil remains workable.
In warmer Southern gardens, there is generally no reason to rush them into warm September soil. Waiting until the weather and soil have cooled in autumn is often preferable.
Autumn-flowering crocuses should be planted earlier, usually in late summer or early September. They need time to establish before their flowering season arrives. Saffron crocus is likewise normally planted in late summer or early autumn.
Where Should You Plant Crocuses?
Crocuses look best when they appear to belong where they are growing.
A single crocus here and another ten feet away can look rather forlorn. Plant them in groups, drifts and irregular clusters instead.
Good locations include sunny flower borders, rock gardens, raised beds, beneath deciduous trees and shrubs, along walks and paths, and in lawns or open grassy areas where they can naturalize.
They are also excellent container plants.
Because deciduous trees have not yet fully leafed out when spring crocuses are flowering, crocuses can thrive beneath them where the ground receives plenty of winter and early-spring sunshine.
For naturalizing in a lawn, remember one important rule: don't mow the foliage down immediately after flowering.
How Deep Should Crocus Corms Be Planted?
For most small spring-flowering crocuses, planting the corms about 3 to 4 inches deep works well. Large Dutch crocuses can be planted somewhat deeper, around 4 to 5 inches.
Plant with the pointed end upward. If you cannot determine which end is which, don't lose sleep over it. The emerging shoot is surprisingly capable of finding its way toward daylight.
Space the corms a few inches apart, or plant them more closely when you want an immediate massed effect.
For a natural appearance, avoid planting them in military ranks. Scatter a handful gently over the planting area and plant them approximately where they fall. Nature seldom uses a ruler.
Sun and Soil
Most crocuses perform best in full sun or light partial shade.
Drainage is more important than rich soil. Crocus corms sitting in cold, soggy ground are invitations to rot.
Ordinary garden soil is generally adequate if it drains freely. Heavy clay can be improved with organic matter and by planting in raised areas where excess water can escape. Rock gardens and raised beds are especially useful for species that demand sharp drainage.
The RHS notes that crocuses generally thrive in sunny, well-drained locations and can grow in borders, turf, containers and beneath deciduous trees.
Caring for Crocuses After They Bloom
Once the flowers fade, leave the foliage alone.
Those narrow green leaves are manufacturing and storing food in the corm for next year's flowers. Cutting or mowing them prematurely weakens the plants.
Allow the foliage to yellow and die naturally. Only then should it be removed.
This is particularly important when crocuses are naturalized in lawns. Delay mowing the crocus area until the leaves have substantially yellowed.
Established crocuses generally require little attention. In favorable conditions the corms multiply, gradually forming larger colonies. Crowded clumps can eventually be lifted and divided while dormant.
Crocuses in the Lawn
Few spring displays are more satisfying than crocuses scattered through an old lawn.
Smaller species are especially well suited to naturalizing. Rather than arranging them symmetrically, scatter the corms by hand and plant them where they land. Over several years the original planting may expand into broad colonies.
The effect can look as though the flowers had always been there.
That is often the difference between merely planting flowers and making a garden.
Small Flowers with a Long History
Crocuses are modest plants. They require little room, little ceremony and relatively little care. Yet they have followed human civilization for thousands of years — from the saffron fields of the ancient Mediterranean to monastery gardens, European estates, cottage lawns and modern American backyards.
Plant the spring-flowering sorts in autumn. Give them sunshine and drainage. Leave their foliage until it dies naturally. Put them where they can multiply.
Then wait.
On some cold morning when winter seems to have overstayed its welcome, a small purple or golden flower will appear almost at ground level.
The calendar may still say winter.
The crocus knows better.
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