Ibulb.com, Holland’s flower bulb promotion bureau, has chosen the crocus (Crocus spp.) as the flower bulb of the year 2015. And why not? It’s one of the most popular bulbs and also one of the easiest to grow.
In nature, crocuses are native to Eurasia, especially around the Mediterranean and in Asia Minor, but also into Northern Africa, mostly in mountainous areas with cold, snowy winters and dry, hot summers. The name crocus itself has very ancient origins, coming from the Sanskrit for saffron (kunkumam). This word evolved into krokos in Greek and eventually into crocus in English.
Spring Flowering Crocuses
This is the most widely grown group of crocuses. There are dozens of species of crocus that bloom from late winter (in warmer climates) into early spring and many varieties are commercially available.
The best known is the Dutch crocus (C. vernus), with its rather large violet, purple, white or bi-colored flowers, the golden crocus (C. chrysanthus), with small flowers that are yellow, white or pale blue inside and marked with brown or purple on the outside, as well as the Tommie crocus (C. tommasianus), with medium-size violet flowers. Various other botanical crocus are occasionally seen in garden centers, including the beautiful tricolor crocus (C. sieberi sublimis ‘Tricolor’).
Crocuses grows from a corm (the equivalent of a bulb). It produces cup-shaped flowers cupped directly from the ground. The leaves are thin and linear, looking more or less like grass leaves.
After flowering, which lasts one to two weeks depending on the temperature (the cooler the spring, the longer the display), the foliage soon disappears and the corm goes dormant for the summer. The return of cool fall temperatures and rainier weather tell the corm it is time to grow… but it starts doing so out of sight, underground, as the roots are the first thing to sprout. The corm will continue to grow under the snow throughout the winter in order to be among the first spring flowers.
This group of crocuses is less well known, although it includes the world’s most widely grown crocus: saffron or saffron crocus (Crocus sativus). It has been cultivated for at least 3500 years. It’s a sterile triploid hybrid species, unknown in the wild, and probably derived from the wild species C. carthwrightianus. It is grown as a agricultural crop for its orange-red stigmas, which are gathered and reduced into powder to make the spice we know. It takes about 150 flowers to obtain 1 g of dry saffron.
Like other fall-blooming crocuses, saffron produces both leaves and flowers in the fall. The flowers are pale violet, normally borne one (more rarely two) per plant.
The saffron crocus is not necessarily the easiest crocus to grow in most places in North America. Our climate is too humid for it taste: it needs a very dry summer and tends to bloom sparsely if at all when conditions are not to its liking. Try it in full sun in an especially well-drained soil, perhaps a rock garden, and avoid summer irrigation.
Other fall-blooming crocus, such as C. zonatus (now C. kotschyanus) and C. cartwrightianus tend to be easier to grow and will even self-sow where conditions are appropriate. Plant them in the fall, as soon as they come on the market.
Fun Crocus Facts
Did you know that…
At about $ 8 a gram, saffron is the world’s most expensive spice?
Crocuses are among the first spring flowers to feed bees in the spring?
Crocus flowers close at night and don’t open until the sun comes out? They don’t open at all on cloudy days.
There are about 90 species of crocus?
Corms can be naturalized in a lawn grass for a very nice effect?
Crocus corms are edible? So if you’re really hungry…
Plant crocuses in late summer (autumn crocus) or fall, from September to November (spring flowering crocus) to a depth three times the height of the bulb (usually about 3 to 4 inches/7,5-10 cm), spacing them about three times their width. Plant them in well-drained soil. It is important to grow them in a location that gets plenty of sun in spring.
Planting bulbs one by one, each in their individual hole at a time, is very tedious. Plus crocuses are more attractive when planted in groups of 12 or more. It is therefore much easier to dig a large, shallow hole with a shovel and to plant many corms in once.
Before placing the bulbs, loosen the soil at the bottom of the hole and mix in bit of bulb fertilizer (optional) and a few pinches of mycorrhizal inoculant (more highly recommended). Afterwards, set the corms in place with the flat side down and the pointed side facing up. Then fill the hole with soil, water well and cover the planting site with mulch.
Under appropriate conditions, crocuses will come back again and again for decades. Some species (C. tomassinianus and C. kotschyanus in particular) will even reseed to create larger colonies. For the others, if you want more, dig and divide the corms when the foliage turns yellow in late spring, then replant immediately.
You will find crocus corms in almost any garden center in the fall. Rarer varieties can easily be found in bulb catalogs on the Internet, such as Brent and Becky’s Bulbs in the USA or Veseys or Botanus in Canada.