(Asparagus officinalis – Family Liliaceae)
Asparagus is a long-lived perennial, grown for its young tender shoots and ornamental foliage, and has been used as food for thousands of years. Pliny the Elder described cultivation methods used by the Romans for producing plants with blanched stems and of a cultivar producing spears of which three weighed a pound. Wild asparagus still grows in Europe, Asia, and northwest Africa; and can be found in dry meadows, sand dunes, limestone cliffs, and volcanic hillsides. It also thrives in notably damp areas near lakes, rivers, or swamps, and near the sea. It even tolerates brackish water and salty soil. The name came through various languages; but the end result seems to have resulted directly from the term “sparrow grass”, used from the 17th century until the 19th when “asparagus” took over, especially when it became a fashionable thought that “sparrow grass” was used only by the illiterate. The term “grass” is still used by some growers and processors.
The Phoenicians are credited with introducing asparagus throughout the entire Mediterranean world, and may have also taken it to Wales. Although the ancient Greeks gathered only wild specimens, the Romans began to cultivate it around 200 BCE; and the area around Ravenna became famous for an exceptionally large variety. The Romans also developed a method of drying asparagus for use out of season. Even 2,000 years ago, asparagus was known as a natural remedy, particularly for its blood cleansing and diuretic properties. It is helpful to know in this case, as well as in reference to other plants, the botanical species name officinalis means “of the dispensary”. This usually means that the plant has had some history as a healing food.
Today, asparagus is prized around the globe for its uncommonly fine delicate taste. The white part of the stalk is woody and tasteless. To find where this begins, bend the stalk; and it will snap back up at that point. This can be cut off and the rest steamed lightly. When asparagus is heated, its chlorophyll reacts with acids in the asparagus or the cooking water to form pheophytin, which is brown. As a result, cooked asparagus turns a drab olive colour. International opinion is divided as to which type is most desirable, with some preferring the blanched, or all white type; while others prefer the green aromatic spears.
Since the 17th century, the green has been truly a royal tradition and used by Royal households and monastaries alike. The custom of blanching asparagus by growing it underground came into fashion toward the end of the 19th century. Since then, a host of recipes have been developed for its use. It is also an important vegetable for the canning industry, especially in China, Taiwan, Spain, and Holland where a large part of the blanched asparagus harvest is devoted to canned or bottled preservation. The colour reveals nothing about the variety but only in the method of cultivation.
Blanched asparagus grows in light sandy soils in mounds that are built up in early spring. Acres of rows that look like a pipeline house these shoots which are hand cut once or twice a day in the main growing season. Once the tips have broken through the soil, they take on colour or open quickly, so they are cut as soon as cracks appear in the mound. Blanched asparagus should be cooked in a bundle in water that contains salt and lemon in order to maintain its white appearance after cooking. It is important to note that the blanched varieties contain substantially fewer nutrients than the green varieties.
Green asparagus is grown in flat beds, completely exposed to the sun. This is the method typical in the US and Britain, while Northern Europe prefers the blanched. Violet or green-tipped spears come from mounded bed and have been briefly exposed to the sun and contain the pigment anthocyanin. This purple type tastes noticeably more bitter than the snow-white type and is popular in France, Spain and Greece. Exceptions are special pink to purple varieties, cultivated in France and California. Because of the high chlorophyll content of the green asparagus, it contains more Vitamin C than the blanched and has a stronger flavour. Sometimes, asparagus spears require a light peeling of the stalk. These peelings can be boiled for ten to fifteen minutes and used as an aromatic stock for soups, or in which to boil the spears. They can be strained and the liquid pressed out of them. There is a rare, and accordingly expensive, asparagus on the market called wild asparagus or baby green asparagus. It is grown as a specialty vegetable in France, where it is prized for its tangy taste. It has a long smooth stalk, with a larger, more noticeable closed flower head. It is only washed and never peeled.
Commercially, asparagus is classified as whole spears, broken spears (with or without tips), and asparagus tips. The more uniform the appearance of the spears, the higher the quality. The best is considered to be those whose spears are straight and have firm closed tips and cut ends, light in colour, fresh, and free from withering or discolouration. Improperly stored asparagus can be recognized by gray or yellow discolourations and an unpleasant musky smell and the lack of “crackle” when the spears are rubbed together. Asparagus does freeze; but, because it is 95% water, it becomes quite limp when thawed. Imported asparagus always lacks flavour compared to locally-grown fresh spears. This is because it begins to lose flavour as soon as it is cut, and long distance travel only enhances the process. On the home front, no matter how tempting, spears should not be cut until the third year after planting. In addition, harvesting them after mid-summer will produce thin spears the following year.
Asparagus is thought to have originated in Eastern Europe and the Middle East, but is now widely cultivated in all temperate and warm countries. Major European producers are Germany, France, Spain, Holland, Belgium, and Greece; but it is also grown in both North and South America and in Africa. It can be grown wherever a light warm soil will provide the ideal conditions for its growth. Asparagus spears are shoots covered with fine, scaly, protective leaves and formed each year from the perennial rootstock. It is always harvested by hand, preferrably early in the morning, which explains its high cost. After the initial harvest, shoots are left to run to seed in order to ensure a good harvest early the following summer. The richly branched foliage then builds up reserves, which are stored in the rootstock. South Africa and South and Central America export asparagus to the Northern hemisphere during the rest of the year.
Asparagus is high in folate, Vitamins A, C, and E, as well as some protein, carbohydrates, fiber, iron, phosphorus, potassium, niacin, thiamin, folacin, and riboflavin. White asparagus contains fewer vitamins than the green, and it deteriorates quickly. In the refrigerator, asparagus will retain all of its folacin for at least two weeks and nearly 80% of its Vitamin C for five days. At room temperature, it can lose up to 75% of its folacin in three days and 50% of the Vitamin C in 24 hours. Canned asparagus may have less than half the nutrients found in freshly cooked spears. White, or blanched, asparagus contains only about 5% of the Vitamin A of fresh asparagus. Asparagus contains asparagine, an amino acid which has calming properties. It is a also a natural diuretic, but excessive amounts can be irritating to the kidneys. In addition, asparagus produces a smelly waste product, the sulfur compound methyl mercaptan, which causes an increase in urine odour. Anyone who lacks the enzyme to break down asparagin will produce this strong odour in the urine. Although harmless, it can be a little disconcerting.
Caution: Asparagus is high in Vitamin K which enables the blood to clot normally. Eating such foods may interfere with the effectiveness of such anticoagulants as heparin and warfarin. Asparagus is also high in purines, which can raise uric acid levels, posing a problem for those troubled with gout.
Varieties of asparagus include the following:
Connover’s Colossal is an old variety that is an early heavy cropper, producing tasty spears that freeze well.
Franklin produces thick spears that can be harvested from two-year-old crowns.
Giant Mammoth has similar characteristics to Connover’s Colossal, but more suited to heavy soils.
Lucullus has long, slim, straight spears.
Martha Washington is an established favourite in the US, and has long spears.