Garden asparagus

How to recognise it

Growth form

Perennial, 1–1.5 m, with upright, much-branched stems from an underground rhizome, the ‘crown’.

Leaf

The true leaves are small brown scales. What look like needles are green, thread-like little stems of 1–2.5 cm in tufts; they feel soft.

Flower

Small, bell-shaped, greenish yellow, 4–6 mm, hanging on thin stalks in the axils. There are separate male and female plants. Flowers in June–July.

Fruit/Seed

Round red berries of 6–10 mm on female plants, with a few black seeds; not edible.

Stem

The young shoots are thick, juicy and scaly: these are the spears. Later the stems become tough, smooth and green.

Roots

A fleshy rhizome with long, thick, cord-like roots that go deep into the soil.

Flowering: June–July · Pruning: February and November

Why grow it?

• A vegetable that keeps cropping in the same spot for ten to fifteen years or more: once the bed is established, you harvest every spring.
• The small bells are visited by bees, especially honeybees and small solitary bees.
• The red berries of female plants are eaten by birds, which spread the seed.
• The fine, airy foliage is decorative in summer and turns a lovely golden yellow in autumn.
• A piece of Flemish food culture: white asparagus Flemish style, with egg, butter and parsley.

Garden asparagus: where does it grow best?

• In the wild in coastal dunes and on sandy, lime-rich, open ground; escaped on verges and along railways.
• Full sun: in shade it produces few spears.
• Loose, deep, well-drained sandy soil or sandy loam that warms up quickly; no wet, heavy clay, where the roots rot.
• In the vegetable garden on a permanent bed at the edge, where it can stay for years without being in the way.

Goes well with

• Parsley: Grows happily at the edge of the asparagus bed and belongs with asparagus Flemish style.
• Pot marigold: A colourful edging that attracts hoverflies and other beneficial insects.
• Lettuce: In the first year, while the asparagus is still small, you can grow lettuce or radishes between the rows.
• Yarrow: In a sunny, dry edge: flat flower heads for hoverflies and parasitic wasps.

Garden asparagus: when and how to plant it?

1. Buy one-year-old asparagus crowns from a nursery or garden centre, preferably an all-male variety: it gives more spears. Never dig up plants in the dunes.
2. Plant in March–April. For green asparagus dig a trench 15–20 cm deep and 30 cm wide, for white asparagus 20–25 cm deep; leave 1–1.2 m between rows.
3. Work compost into the bottom of the trench and lay the crowns 30–40 cm apart, with the roots spread out like a spider.
4. Cover them first with 5 cm of soil and gradually fill the trench during the summer as the stems grow.
5. Water after planting and in dry spells during the first year.
6. Do not harvest for the first two years, so the plants grow strong; in the third year harvest for a few weeks, then longer each year.

Care

Water

Weekly in dry spells in the first year. After that its deep roots look after it; but do water in a dry spring for good spears.

Feeding

Asparagus is a hungry crop: every year after harvesting, in June, give a layer of compost or well-rotted manure.

Harvesting

From mid-April to the end of June. Cut green spears when they are 15–20 cm long; dig white ones out of the ridge as soon as the tip cracks the soil. Stop around 21–24 June so the plant can build up strength.

Weeding

Keep the bed weed-free: asparagus copes badly with competition. Weed by hand, as deep hoeing damages the buds.

Support

The tall foliage can blow over: run a string along the row.

Tip: Be patient: harvest nothing for the first two years and then stop every year around 21–24 June. An asparagus bed that is given the chance to build up strength will give thick spears every spring for ten years or more.

Pruning and mowing

Pruning months: February and November.

When: In November, cut down the yellowed foliage; on a healthy bed in a nature garden it can stay until February.

How:

• After harvesting, let the foliage grow freely: it feeds the roots for next year.
• Cut the foliage down to 5 cm above the ground once it has turned completely yellow in autumn.
• If the foliage had asparagus beetle or rust, put it in the household waste, not on the compost heap.
• On a disease-free bed the foliage can stand until February: birds eat the berries and small insects overwinter in the stems.

Caution: Never cut the foliage while it is still green: you would weaken the plant and get fewer, thinner spears next spring.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Sow in March–April indoors or in May outdoors, in small pots; germination is slow. After a year you have crowns ready to plant, but it then takes another two years before you can harvest.

Division

Old crowns can be lifted and divided in March, but they establish less easily than young plants.

Garden asparagus: how does it get through the winter?

Hardy to −25 °C.

• The foliage turns golden yellow in October–November and dies; the rhizome overwinters deep in the soil.
• Fully hardy: the crowns tolerate severe frost.
• A layer of compost over the bed in late winter protects and feeds the roots.
• If you leave the foliage, birds eat the red berries and small insects overwinter in the stems.

Diseases and pests

• Asparagus beetle: Red-and-black beetles with cream spots and grey larvae that strip the foliage. Pick them off in summer and clear the foliage in autumn.
• Asparagus fly: Its larvae tunnel into the spears, which then grow crooked. Remove affected stems.
• Rust: Orange to brown pustules on the foliage in summer. Clear the foliage in autumn and do not plant too closely.
• Wet feet: On wet, heavy soil the roots rot. Plant on a raised bed or on sandy soil.
• Perennial weeds: Couch grass and other perennial weeds are almost impossible to remove from an asparagus bed. Clear the soil thoroughly before planting.

Through the year

• February: Cut down foliage left standing over winter. Spread compost over the bed.
• March: Plant new crowns in a trench.
• April: From the third year, harvesting begins. Earth up white asparagus.
• May: Main harvest. Weed by hand.
• June: Stop harvesting around 21–24 June. Feed with compost. Flowering begins.
• July: Flowering; the foliage grows freely. Pick off asparagus beetles.
• August: Water in dry spells. Red berries on the female plants.
• September: The foliage feeds the roots. Birds eat the berries.
• October: The foliage turns golden yellow.
• November: Cut yellow foliage down to 5 cm; do not compost diseased foliage.

Did you know?

• The ‘needles’ of asparagus are not leaves but flattened side shoots. The true leaves are the small scales on the spear, which you can see on the tip of an asparagus spear.
• White and green asparagus are the same plant: white spears grow in the dark under a ridge of sandy soil, green ones emerge into the light and make chlorophyll.
• After eating asparagus, many people’s urine smells noticeably, because of sulphur compounds from the plant. Not everyone can smell it.