A frequent subject in poetry and art, crocus are considered by many to be the first sign of spring.
Typically beginning to bloom in late February to early March, crocus produce delicate purple, violet, white, lilac, and yellow blooms. Spring-blooming crocuses are often planted in lawns or at the edges of garden beds or paths. These cheerful flowers are certainly a welcome beacon of warmer days after the cold months of winter.
The genus Crocus includes around 100 species of small, flowering perennials. About 30 to 40 species are cultivated. Some species bloom in spring while others bloom in fall. Although they are cormous, crocuses are often grouped together from a horticultural perspective with bulbous plants such as daffodils and tulips since they require similar care and growing conditions.
Where are they from?
Crocuses are native to Europe, the Mediterranean, and central and western Asia. While there aren’t any crocuses native to Missouri, none are considered aggressive in garden settings.
Just like people, crocuses love sunshine and crocus flowers close up at night or on cloudy days. This phenomenon is called nyctinasty. Charles Darwin theorized this plant movement was to protect against low temperatures, but the most widely-accepted theory is flowers close to protect pollen from dew and rain.
How are they pollinated?
Bees are the main pollinator for crocus, although some species are pollinated by beetles.
As an early-blooming spring flower, crocus provides valuable pollen for bumble bee queens. These insects hibernate all winter and emerge in early spring when they have few resources as many flowers don’t bloom until later in the season. Crocus are key to keeping the queens fed until more plants begin to bloom. Crocus also provide essential feed for bee species that emerge only in spring, and complete their lifecycle before summer.
Crocus at the Garden
Hundreds of crocuses bloom across the Missouri Botanical Garden each spring. The Heckman and Samuels Bulb Gardens is home to eight different crocus species in the bulb garden, and a handful of cultivars.
Crocus tommasinianus, the snow crocus, is the most common at the Garden. This is the delightful little lilac species that pops up around the bulb garden, in the lawn, and in an impressive display outside of the Mausoleum. It has cultivars ranging from purple to white.
Growing the Garden’s Collection
Since crocus are perennialize and naturalize, Garden horticulturists don’t have to replace bulbs each year as they do with other spring flowers like tulips. However, the Garden staff plants new species each year to enhance the diversity of the crocus collection. Over the past five years staff have targeted over 60 species for the collection acquired through international botanical exchange programs, purchases from specialist growers, or when possible, collecting seeds from wild populations.
All of these methods rely on numerous protocols and professional networks. The Garden uses research tools to gather data on habitat, cultivation techniques and survivability before we have the opportunity to nestle bulbs into the ground. The whole process can take years for just a single species.
Crocus in Your Yard
Planting crocus in lawns is a very easy way to add a pop of color to your late winter or early spring landscape. Crocus grow best in very well-draining soils in full sun. They can also be grown in partial shade, as long as they get at least four hours of direct sun. They also prefer being somewhat dry in the summer while dormant.
The best time to plant crocus corms is in the fall. In St. Louis, temperatures should be cool enough by mid-October to start planting most spring-flowering bulbs and crocus. Follow these steps from the Kemper Center for Home Gardening to plant crocus in your lawn:
- Use a spade to remove clumps of turfgrass and set them aside.
- Amend the soil if necessary to improve drainage to a depth of around 6-8 inches.
- Plant the corms with the pointed side facing up, roughly 3-4 inches deep and 6 inches apart. This may seem like a lot of space for such small corms, but this will give them room to form offsets.
- Replace the turfgrass clumps and water everything well.
- Wait until the crocus foliage turns yellow after blooming before mowing again in the spring. This will allow the plants to gather plenty of energy for next year’s flower display.
The most popular spring-blooming crocus species and hybrids include:
Crocus vernus (Dutch crocus)
The large blooms of this species come in an array of purple shades as well as white and striped selections.
The most common yellow-flowering crocus, this hybrid is often found in Dutch crocus mixes. Its parentage includes C. angustifolius and C. flavus, two yellow-flowered species. Popular cultivars include ‘Golden Yellow’ and ‘Yellow Mammoth’.
Crocus chrysanthus (snow crocus, golden crocus)
One of the earliest blooming species. In the wild this plant has golden yellow to orange blooms, but white, purple, and blue selections are available. Also widely used in hybridization.
Senior Public Information Officer
Many thanks to Garden Horticulturists Claire Krofft, Justine Kandra, and Travis Hall and Butterfly House Science Education Coordinator Chris Hartley for expert information provided.