Asparagus (Asparagus officinalis)
Asparagus has very few close botanical relatives in its own family, Asparagaceae. The name “asparagus” simply comes from the Latin botanical title, with its roots in Greek and the original Persian, asparag, meaning “shoots.” The asparagus we eat, of course, are actually the young shoots of a large perennial plant, harvested shortly after appearing above ground in the spring. The shoots issue forth from an underground stem (crown), and if left to mature, form a dense cloud of diaphanous green foliage. The fern-like leaves are actually modified stems called cladodes, which emerge from the crutches of true scale leaves close to the main stalk. Tiny, pale yellow to white flowers appear in mid-summer. Most asparagus types are dioecious, with male and female flowers appearing on separate plants. All-male varieties like Guelph Millennium and Jersey Knight are thought to be generally more productive of spears, and they do not spend energy creating the tiny, red, berry-like fruits that will appear on some female plants after flowering. These fruits are said to be somewhat poisonous to humans.
Asparagus was cultivated as far back as ancient Egypt, and recognized for centuries in medicine for its diuretic properties. The Greeks and Romans enjoyed it as a fresh vegetable, and dried it for winter use. A recipe for asparagus is included in the first known cookbook, by the author Apicius in the 3rd century AD. Asparagus lost its popularity in the middle ages, but then reappeared as a delicacy in the late 17th century. Louis XIV loved it, and encouraged its cultivation across France.
White asparagus (spargel) has been grown in northern Europe for centuries. This is harvested just as the shoots emerge from the ground. Otherwise, it is grown with very low light levels, and high ultraviolet exposure. White asparagus has a rather more subtle flavour. Purple asparagus shoots were developed in Italy, and contain a higher sugar content than their green and white counterparts.
Asparagus is an excellent source of iron, folate, potassium, thiamine, and riboflavin, among other nutrients, including beta carotene. Famed as an aphrodisiac, asparagus also produces little understood organic compounds that create a strong, fetid smell in the urine of those who eat it. It remains unclear if this phenomenon occurs for all who eat asparagus, or if all people can detect the smell. Marcel Proust wrote that asparagus “transforms my chamber-pot into a flask of perfume.”
Thought to have originated in maritime regions, asparagus can stand higher levels of salinity in the soil than many plants. Some traditional growers actually add salt to the soil, but this is not recommended, for few other plants could ever be cultivated in the same site again. It is an excellent companion plant for tomatoes, as the asparagus beetle is repelled by the smell of tomato plants. At the same time, asparagus seems to repel some harmful root nematodes that can damage or kill tomatoes.
Every year since 1985, for three days in late April, the town of Stockton, CA, has celebrated its annual Asparagus Festival. Festival-goers consume as much as 36,000 lbs of asparagus donated to raise money for local and regional charities. What could be better?
One final reward of growing your own asparagus and using it fresh is that just about all the world’s supply of supermarket spears are imported from Peru, China, and Mexico. In terms of “eating local,” it’s hard to beat this particular crop.
How to Grow Asparagus:
Difficulty: Asparagus from seed requires a major investment of time, work, and space, but it is one of the most rewarding homegrown vegetables, and well-tended plants may be productive for a decade or longer. Asparagus is not suitable for containers.
Timing: Start seeds indoors February to May. You will start harvesting these long-lived perennials 3 years after planting.
Sowing: Soak seeds for 2 hours. Plant 1 seed per 5cm (2”) pot, 2cm (½”) deep. Keep in a warm place. Be patient: they can take 2-8 weeks to sprout depending on soil temperature. Transplant when seedlings are 10-12 weeks old and danger of frost has passed. Space 45cm (18”) apart in rows 1-2m (3-6’) apart. Place each plant in a hole 10cm (4”) deep and gradually cover the crown with soil as it grows. For thicker spears, space the plants 30-35cm (12-14”) apart and set buds15-20cm (6-8”) in the hole. For thinner spears, space 20-25cm (8-10”) with the buds 10cm (4”) deep.
Soil: Beds are permanent, and must be fertile and cultivated deeply — aim for a pH of 6.5-7.0 with lots of organic matter.
Growing: Fertilize after harvest and again in spring with 1-2 cups of complete organic fertilizer per 3m (10’) of row, worked in lightly. Asparagus needs 2cm (1”) of water per week. In late fall, trim ferns down to 5cm (2”) and remove cuttings to avoid future disease and insect problems.
Harvest: Don’t harvest until the third year. Then harvest over a 2-3 week period. Cut the fattest spears off at ground level when they are 15-20cm (6-10”) long. When thinner spears begin to emerge, let them grow into big fronds to nourish the roots. Each successive year the harvest lengthens, to a maximum of 6-8 weeks. Even when planting Asparagus Crowns, it’s a good idea to not harvest during the first season of growth. This allows the root system to become stronger before harvest begins.
Storage: Refrigerate immediately after cutting. For the home grower, cutting asparagus as needed for meals during the relatively short harvest window is a good idea, as the stalks quickly lose their crispness. Asparagus can also be blanched and then frozen. For a real treat, try pickling some as you would beans.
Seed info: In optimum conditions at least 75% of seeds should germinate. Soil temperature for germination: 21-30°C (70-85°F). Usual seed life: 2 years.
Growing for seed: Not really practical in this region, even with open pollinated varieties.
Pests & Diseases: The primary pest of asparagus is the asparagus beetle. These usually do not show up in infestations, and can be easily hand-picked from the plants. Avoid Fusarium wilt by obtaining healthy crowns or by growing from seed. If Fusarium is present, burn the plants. The best strategy with asparagus is to raise vigorous plants that have innate disease and pest resistance.