Asparagus

Family

Asparagaceae

Habit

perennial

Height

1.5 m

Spread

0.8 m

Growth

medium

Lifespan

20 years

First yield

after 3 years

Full yield

after 6–7 years

Productive years

15–20 years

Hardiness

zone 4–9

Shade tolerance

light shade

Soil

Sand, Silt, Loam

Soil moisture

semi-dry – very moist

pH

5.6 – 7.6

Times apply to the northern hemisphere in a temperate climate and shift with altitude and cultivar.

Edible: What is eaten are the young shoots, and the harvesting method decides the colour: white asparagus is cut before the shoots break through the crown of the ridge, green asparagus grows above ground and forms chlorophyll in the light, and purple asparagus sits between the two. In Europe harvest runs from March to June depending on the region. Germany today favours white asparagus, while the English-speaking world — as Germany once did — prefers green. Classically the spears are peeled and boiled or steamed in salted water; green asparagus barely needs peeling and takes well to frying and grilling. Thin spears can be shaved raw into a salad. Beyond that come soup made from the peelings, quiche and risotto. The red berries of the dioecious cultivars are mildly toxic and do not belong on the plate.

Other uses: The uses beyond the harvest are modest for asparagus and often overstated. Real is the floristic one: the fine needle-like summer foliage and the red berries of female plants work as cut greenery and dried decoration, which is why related species of the genus are grown as ornamental asparagus. As a deep-rooting rhizomatous perennial it also binds loose sandy soil. Two widespread claims, by contrast, deserve caution: that asparagus repels nematodes attacking tomatoes, and conversely that tomatoes keep asparagus beetle away, is a common companion-planting rule but not solidly evidenced — the asparagusic acid in the roots inhibits nematodes in laboratory tests, which says nothing yet about garden practice. As a medicinal or dye plant it plays no role.

Site: Asparagus is a permanent crop — a well-made bed yields for 15 to 20 years, so the choice of position holds for two decades. It needs full sun and a loose, sandy, deep and stone-free soil without waterlogging; on heavy or stony ground the spears grow crooked. The spot must stay permanently clear, because any cultivation nearby damages the root system lying shallow beneath the ridge. Important for planning: never follow asparagus with asparagus — a new bed belongs elsewhere, or soil sickness and Fusarium catch up with the young planting. Tomatoes, parsley and basil count as favourable neighbours. And one decision falls at the point of purchase: today's all-male hybrids set no berries, while old dioecious cultivars carry red, mildly toxic berries that attract small children and self-seed. After harvest the shoots grow up to one and a half metres and shade their surroundings. Care: To make the bed, dig a trench of about 30 centimetres in autumn, work manure or other organic matter into the base, set one- or two-year-old plants — called crowns for their long fleshy roots — in spring and cover them with soil; the trench is filled in over the course of the year. From the third year on, throw up a knee-high ridge over the row and start harvesting; green asparagus grows without a ridge. The season traditionally ends on 24 June, Midsummer Day: after that the plant needs its foliage to build reserves for next year. In autumn cut and remove the stems to deny asparagus fly and fungi a foothold, and apply compost. The main pests are asparagus beetle and spotted asparagus beetle, asparagus fly, asparagus rust and Fusarium; deer and hares readily eat the young shoots.

From seed it takes a long time: sow in March under glass or in April outdoors, with germination taking three to four weeks at around 20 degrees. The seedlings are grown on for a year into so-called crowns, which go to their final position the following spring — buying one- or two-year-old crowns saves exactly that time and brings the first harvest forward by a year or two. Dividing the rhizome is possible but gives weaker plants and is only worth it to preserve a particular old specimen. Note that the cultivars grown today are all-male hybrids and cannot be reproduced from seed; only the old landraces such as Ruhm von Braunschweig or Huchels Leistungsauslese come true and are maintained from seed. The first worthwhile crop comes in the third year after planting.

Asparagus is a good example that low species numbers do not mean low value. NaturaDB records only a single wild bee species on it — the asparagus mining bee (Andrena chrysopus) — but that one is specialised on it and cannot live without asparagus. Two moth species whose caterpillars feed on it follow, the bright-line brown-eye (Lacanobia oleracea) and the beet armyworm (Spodoptera exigua), plus two beetles that count as pests in cultivation while equally being part of biodiversity: the asparagus beetle (Crioceris asparagi) and the spotted asparagus beetle (Crioceris duodecimpunctata). The USDA report rates asparagus "+" for both honeybee nectar and pollen, meaning attractive under certain conditions, and notes that pollination is required for seed production — which applies only to the dioecious cultivars, since today's all-male hybrids flower without setting fruit. The red berries are eaten by birds, which disperse the seed, and the delicate summer foliage gives small animals cover. To raise the value, leave the foliage standing until spring.

Notable: a dioecious rhizomatous perennial whose bed yields for 15-20 years; the season traditionally closes on Midsummer Day, 24 June → "cherries red, asparagus dead"; 1952 saw the first hybrid cultivar "Schwetzinger Meisterschuss", 1975 the first all-male one, "Lucullus" → almost only such cultivars are grown today; the East German cultivar "Eros" was the first tetraploid+stood out for unusually thick spears; by area Germany's most important field vegetable;

Eastern Mediterranean, now cultivated worldwide. The home of garden asparagus is taken to be the eastern Mediterranean; wild ancestors and relatives occur in central and southern Europe, the Near East, western Siberia and North Africa. It is locally naturalised in South and North America and in New Zealand. Whether the stands on the gravel and sand banks of the Rhine, Main and Danube already mentioned by medieval authors are genuinely wild or derive from escapes is unresolved. In Germany asparagus is the most important field vegetable by area: the acreage grew from 15,500 hectares in 2000 to about 28,500 hectares by 2018, with the largest shares in Lower Saxony, North Rhine-Westphalia and Brandenburg — those three states alone account for more than half.

Naturalised asparagus grows in Central Europe on dry, moderately nutrient-rich, sandy sites: on embankments, along path margins, in dunes and in ruderal dry grassland. Phytosociologically it occurs mostly in grey hair-grass communities (Corynephoretalia), but also in fringe communities of the Origanetalia and in semi-dry grassland of the Festuco-Brometea. The pattern fits its build: as a deep-rooting rhizomatous perennial it stores reserves underground, shoots quickly in spring and copes well with summer drought, while avoiding waterlogging, compaction and stony ground. Its natural habitat is therefore open, warm and sandy — the classic asparagus districts on the sands of Brandenburg and the Lower Rhine reproduce exactly those conditions.