in having high sugar and low fibre levels. Purple asparagus was originally developed in Italy, near the city of Albenga and commercialized under the variety name 'Violetto d' Albenga'. Purple asparagus can also turn green while being cooked due to its sensitivity to heat. Companion planting Asparagus is said to be a useful companion plant for tomatoes, as the tomato plant repels the asparagus beetle. Asparagus may repel some harmful root nematodes that affect tomato plants. Uses Only young asparagus shoots are commonly eaten: once the buds start to open ("ferning out"), the shoots quickly turn woody. The roots contain starch. Water makes up 93% of asparagus's composition. Asparagus is low in food energy and very low in sodium. It is a good source of vitamin B6, calcium, magnesium, and zinc, and a very good source of dietary fibre, protein, beta-carotene, vitamin C, vitamin E, vitamin K, thiamin, riboflavin, rutin, niacin, folic acid, iron, phosphorus, potassium, copper, manganese, and selenium, as well as chromium, a trace mineral that regulates the ability of insulin to transport glucose from the bloodstream into cells. The amino acid asparagine gets its name from asparagus, from which it was first isolated, as the asparagus plant is relatively rich in this compound. The shoots are prepared and served in a number of ways around the world, typically as an appetizer or vegetable side dish. In Asian-style cooking, asparagus is often stir-fried. Cantonese restaurants in the United States often serve asparagus stir-fried with chicken, shrimp, or beef. It may also be quickly grilled over charcoal or hardwood embers, and is also used as an ingredient in some stews and soups. In recent years, asparagus eaten raw as a component of a salad has regained popularity, although may cause digestive issues for some. Asparagus can also be pickled and stored for several years. Some brands label shoots prepared in this way as "marinated". Stem thickness indicates the age of the plant (and not the age of the stalk), with the thicker stems coming from older plants. Older, thicker stalks can be woody, although peeling the skin at the base removes the tough layer. Peeled asparagus will poach much faster. The bottom portion of asparagus often contains sand and soil, so thorough cleaning is generally advised before cooking. Plants bearing seeds produce spears that are smaller and thinner, and plants without seeds produce larger and thicker spears. Thickness and