"For years I kept records of when the first flowers came out, and I still do as a matter of fact."
--Henry Francis du Pont (1880-1969)
It looks like grass, but it's not. It's the beginning of "Remembrance," the shoots from a forgotten corm planted late last fall. Soon the sleepy yard, dotted with islands of snow, will be blanketed with hundreds of silvery purple flowers and their wispy, light-green leaves--an early spring gift from Mother Nature.
For gardeners, crocuses are dream plants: durable, remarkably colorful, and blossoming at the most unexpected times of the year. The shoots are diminutive-rising barely three to six inches from the ground--but the flowers they bear vary in color from pale purple to bright yellow and white, some decorated with accents or stripes. The most highly valued species is the source of saffron--a coveted spice and colorant that has enjoyed an important place in traditional medicines.
The plants are generally found in moderate to cold climates. They grow best in well-drained soil that consists of a loam halfway between clay and sand. For a majority of species, favorable growing conditions occur in the Mediterranean region, especially around Turkey and the Balkans. Some varieties can be found as far north as Poland, east to Russia and western China, west to Portugal and Morocco, and south to Jordan and Iran. As cultivars, they are grown in gardens the world over.
More than 80 species have been classified in the genus Crocus --an ancient Chaldean name for saffron given by the Greek botanist Theophrastus. Most species, including the Dutch yellow crocus (C. flavus) and the popular alpine species (C. vernus), bloom in early spring; but some--such as C. speciosus, which produces violet-blue flowers with orange accents--blossom in the fall. The saffron-producing species, C. sativus, also bears purple flowers that bloom in the fall. James Bauml, senior biologist at Arboretum of Los Angeles County in Arcadia, California, considers that his favorite species. "It does pretty well in our climate, and saffron's a useful spice," observes Bauml.
Corms and flowers
Crocuses are usually grown from corms. A corm looks like a miniature bulb, and as in the case of a bulb. Its root system develops from the wider end, or plate. But aside from similarities in shape and function, a corm is very different from a bulb. The body of a corm has several nodes and internodes--it is therefore a specialized stem. A bulb, on the other hand, is made up of fleshy leaves that are attached at the base to a relatively small, compressed stem.
The crocus flower, carried aloft on a thin tube, has six petals and three stamens, The stamens split open and bend outward to release their pollen. The styles (stalked portions of the central, female part of the flower) vary from species to species, but in the simplest case each style divides into three branches. The styles also vary in color from yellow to dark red or brown.
Like many perennial bulbs, the crocus flowers in response to a change in ground temperature. The process, called vernalization, requires that the corm be exposed to temperatures of 2-5 [degrees] C (36-41 [degrees] F) for an extended period of time and then warmed up. In milder climates, cultivars are refrigerated for up to six weeks to simulate this process.
The genetic material utilized for the new season's growth and flowering is safely tucked away within tissue known as the shoot apical meristem near the top of the corm. With the slightest rise in temperature, the plant's food energy will be spent activating plant growth, which generally culminates in the production of one flower. In the wild, a single corm may produce flowers for up to 12 years, while a commercial farm will replant every 3-4 years.
What triggers the season's new growth is still unclear. "The genes or proteins that are sensitive to the vernalization treatment are not known yet," explains Mary Williams, assistant professor of biology at Harvey Mudd College in Claremont, California. "It has been shown, however, that the cells in the shoot apical meristem are the ones that must be vernalized. In fact, if these cells are the only ones vernalized, the plant can still be induced to flower."
Each season, the parent corms are completely depleted by the above-ground stems, leaves, and flowers. During the flowering and fruiting stage, a new corm is produced as a branch on the parent corm, which gradually withers away. The new corm develops contractile roots, preventing it from rising to the surface. At the same time a number of tiny offspring called cormels sprout from the parent corm.
Crocuses reproduce either vegetatively, from corms, or sexually, by pollination and seed production. The former is the quicker route to obtain flower-sized stock. To help with this process, the residual cormous material is dug up after the leaves have died, and the new corm and smaller cormels are separated and replanted. The corm generally flowers the following year, but the cormels need extra care to mature. This method of is equivalent cloning, in the sense the genetic material the new plant is identical to that of the parent.
In nature, cross-pollination is helped along by bumble bees, beetles, and, for some autumn-flowering species, months. But in nurseries, the same process is conducted by hand requires patience and skill. The pollinated plants have to be carefully shielded from receiving pollen from other sources.
A crocus its ovary below ground level. Upon fertilization, the ovary is pushed to the surface of the soil along an elongated scape that grows from the of the corm. For the autumn-blooming species, this process is postponed until the warmth of spring coaxes the plant out of dormancy. By late spring, the seeds of both spring-and autumn-flowering species reach maturity, and each capsule that protected the embryos opens into three petal-like leaves, dropping the seeds the ground, where they germinate and form new corms.
Collecting and planting the seeds will produce many corms under the right growing conditions. But it often takes up to two seasons before these corms will flower. In some cases, such as with the Dutch yellow crocus and the saffron species, the plants are sterile and cannot set seed, so they propagate themselves vegetatively.
An epicure's gold
Saffron is an epicure's fine gold. An ounce of saffron now fetches $55-100. There was a time when a person caught tampering with the product faced the penalty of death. The Book of Spices (Livingston Publishing Co., 1969) records that in 1456, saffron trader Elsa Pfragnerin of Nurnberg, Germany, was buried alive his adulterated product.
Pure saffron consists mostly of bright red stigmas intermixed with a few yellowish ones, but the latter contribute no flavor. Chemical analysis shows that saffron contains crocin, a powerful pigment capable of imparting an unmistakable yellow color to 150,000 parts of water.
Producing the spice is a labor-intensive process [see "A Gift of Spice," The World & I, October 1995, p. 226]. A harvester armed with a pair of tweezers pulls three red stigma "threads" from each flower. The stigmas are then dried, either in the sun or by artificial means, losing about 80 percent of their weight in the process. It takes about 4,000 crocuses to produce an ounce of saffron.
Three hundred years ago, saffron was the "snake oil" that cured all ailments. It was considered an effective stimulant, depressant, expectorant, emmenagogue (inducing or increasing menstrual discharge), and antispasmodic. In sixteenth-century England, a jolly person was said to have "slept in a bagge of saffron."
The history of saffron in folkloric medicine includes its use as an emmenagogue and an abortifacient. But according to The Lawrence Review of Natural Products, there is no evidence to support saffron's use for these purposes. In fact, James Duke's Handbook of Medicinal Herbs reports that large dosages of saffron, when used as an abortifacient, have resulted in fatalities.
Nonetheless, recent research suggests that saffron may be useful in other medical treatments. In 1996, researchers from the University of Castilla-La Mancha, Spain, reported that crocin extract inhibits the growth of human tumor cells in vitro. They noted, however, that additional work will be needed "to unravel the specificity and usefulness of crocin... as well as the possible role of saffron spice as a chemopreventive dietary component."
In a couple other studies, John Gainer at the University of Virginia has reported that when rabbits were injected with crocetin (a component of crocin), their cholesterol and triglyceride levels were lowered by as much as 50 percent, compared with a control group. According to The Lawrence Review of Natural Products, this observation, when considered with epidemiological evidence, "suggests that the low incidence of cardiovascular disease in parts of Spain may be related to the liberal, almost daily consumption of saffron."
Nearly 250 years ago, a deceptively delicate crocus variant was introduced to the Swiss Alps. Today, a descendant of that plant dances joyfully in the breeze just beyond the glass doors that lead to the backyard,its flowers glistening in the pale spring sunlight. Reaching for a tattered notebook with a faded pansy pasted on the front, I turn to a blank page and write, "C, vernus--`Remembrance.'"
Patricia Maxwell-Florez is a for Future Watch, a weekly radio program that highlights issues in science, technology, and the environment. The program is distributed by the National Public Radio Satellite System. She gratefully acknowledges the expert advice and assistance of James Bauml, senior biologist at the Arboretum of Angeles County in Arcadia, California; Mary Williams, assistant professor biology at Harvey Mudd College in Claremont, California; and Leslie Baer, author of Earth Keepers.
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|Publication:||World and I|
|Date:||Mar 1, 1998|
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