What is asparagus and how is it grown?
"Spargel" (also known as "Bleichspargel" - bleached asparagus) is the German word used to mean white asparagus. Green asparagus is called "Grünspargel" or "grüner Spargel" and is harder to find in Germany.
Asparágus officinalis L. is the edible shoot of the cultivated plant in the taxonomic family Asparagaceae with over 300 species. It is closely related to the Lily (Liliaceae) family. Asparagus shoots arise from underground rhizomes (a type of stem) early in the spring. Because the plant is a perennial, asparagus is one of the first fresh vegetables on the market.
Both green and white asparagus are the same species, but crop breeding over the last couple thousand years has produced "varieties" and hybrids which have different growth characteristics. That is why you cannot turn white asparagus successfully into green asparagus by letting it grow out of the dirt.
Asparagus evolved in dry climates and likes sandy, well-drained soils. Knowing that, it is amazing that the shoots consist of up to 95% water! Asparagus is very low in calories, but has many vitamins and minerals; green asparagus has more nutrients than white.
White varieties such as Backlim, Boonlim, Ravel, and Braunschweig have been bred for thick shoots, closed heads and a mild, non-bitter taste. White asparagus is harvested in Germany between April and June 24th of each year. The farmer hills up sand and compost over the root stocks to blanch the shoots as they grow. Asparagus shoots can grow 2-3 inches per day in warm weather.
Green varieties such as Reading, Giant, Palmetto or Martha Washington have been bred with a lower anthocyanin (the purple pigment) content, which reduces bitterness. They are not as thick or as woody as white varieties and do not have to be peeled.
Violet asparagus, loved in some countries such as France, is considered inferior to white asparagus in Germany. The color develops when the white asparagus breaks through the dirt crust and light shines on it.
Purple varieties, Violetto d'Albenga, Purple Passion, are bred for a nutty flavor, have up to 20% more sugar and less fiber than green asparagus. It is a new variety and not seen often in stores.
Growing white asparagus is an intensive process and it takes at least three years until the first harvest. Root stocks (they are rhizomes, but commonly called roots) are set out in early winter and the plants allowed to grow and flower for two years. In the third year the farmer mounds sand and compost over the root stocks and hopes for a warm spring.
During harvest, workers go out every morning before sunup and pick asparagus by digging a small hole, sticking a sharp knife into the dirt, aiming for the base of the shoot, carefully pulling out the shoot and filling in the hole with sand using a trowel. Mechanization has not worked because a broken asparagus shoot has very little value. For more in-depth information, I recommend this two-and-a-half minute film by Food-Travels.com about the asparagus growing process in Germany.
Germany has divided asparagus into strict quality classes, comparable to USDA Grade A, Choice, etc. The classes of "Spargel" are:
Extra - Minimum diameter of 12 mm (15/32 inch), no hollow cores, perfectly straight and all white. Most expensive.
Handelsklasse I (HK I) - Minimum diameter of 10 mm (3/8 inch), light bending, light coloration (violet). Good value.
Handelsklasse II (HK II) - Minimum diameter of 8 mm (5/16 inch), curved stalks allowed, slightly opened flower heads, more color than HK I and sometimes woody. Good for soup stock and students.
No matter which quality you choose, the asparagus should be fresh or you are throwing your money away. Fresh asparagus has moist cut surfaces, can be dented with a fingernail and smells sweet, not sour. Do not touch the asparagus at the German market, however, unless you want to be yelled at by the seller. Ask for a sample and find a seller you can trust by asking friends and relatives.