Overview
What asparagus needs, when it crops, and whether you have room for a permanent bed.
Asparagus is the vegetable you plant for the next decade or two. The spears are stems pushing up from an underground crown, and in a warm spell they can grow 5 cm (2 in) in a day. The price is patience: the crowns need two or three years to build their roots before you cut, and every summer the spears you leave become tall ferns that feed next spring’s crop.
Quick facts
- Botanical name
- Asparagus officinalis
- Soil pH
- 6.5 – 7.0
- Feeding
- Moderate feeder
- Hardiness
- USDA zone 5b and warmer
- Height
- Up to 240 cm (94 in)
- Propagation
- Seed, Division
Survives −25 °C
Growing details
- Germination
- 21 days
- Spacing
- 45 cm (18 in)
- Sowing depth
- 25 mm (1 in)
- Frost sensitivity
- Frost hardy
Growing calendar
- Start indoors: February
- Plant out: March, April
- Harvest: April, May, June
- Dormant: January, February, November, December
At 13 to 16 °C (55 to 61 °F); grow on for a year before the final planting. Crowns in early spring, as soon as the soil can be worked; later in cold regions. From the second or third spring after planting crowns; stop by mid-June. Cut the ferns down once they turn yellow.
Is this plant right for you?
- Perennial vegetable
- Needs a permanent bed
- Raised-bed friendly
- Frost hardy
- Crops for 10 years or more
- Needs patience
- Drought tolerant once established
Good to know
It stands frost, so it can go out earlier than tender crops.
Before You Grow
Choose all-male crowns and a sunny, well-drained, weed-free spot you won’t want back for years.
Clear every perennial weed before you plant: you can’t dig the bed once the crowns are in.
What you need
One-year-old crowns
Full, slightly moist roots and visible buds. Dry, brown or soggy black roots mean poor storage. See choose crowns or seed.
A permanent, weed-free bed
Several square metres, in full sun, that you won’t want back for years. See where it grows best.
Compost or well-rotted manure
At least a bucketful per square metre dug in before planting, and a mulch every year after.
A spade for the trench
A trench is quickest for a whole bed. See planting crowns.
Stakes and twine
To hold up the ferns in summer. See weeding, support and cutting back.
A sharp knife
For cutting spears below the soil, from the third spring.
Crowns or seed, male or female
Crowns or seed. Crowns are the usual choice: dormant one-year-old plants, sold bare-root in spring. They settle in faster and you can cut spears sooner. Seed is far cheaper and one packet gives many plants, but seedlings need more care and delay the first harvest: by a year, say the RHS and the University of Maryland; Gardeners’ World says wait at least five years.
Male or female. Asparagus plants are either male or female. Male plants give more spears, live longer and don’t set seed, so most modern varieties are all-male hybrids. Female plants give fewer, larger spears, carry red berries, and drop seed that comes up as weedy seedlings in the bed.
Colour. Green is the usual spear, and some varieties are purple. White asparagus is not a variety: it is ordinary asparagus grown in the dark (see harvesting).
Varieties compared
-
Guelph Millennium
- Plants
- All male
- What stands out
- Very cold tolerant, high yield, suits most soils
-
Mondeo
- Plants
- All male
- What stands out
- Early, high yield, good disease resistance; spring or autumn planting
-
Gijnlim
- Plants
- All male
- What stands out
- Early; green spears with purple tips
-
Jersey Knight / Jersey Giant
- Plants
- All male
- What stands out
- Heavy croppers with good disease resistance; no longer propagated, so getting scarce
-
Connover’s Colossal
- Plants
- Male and female
- What stands out
- Reliable heritage variety
-
Mary Washington
- Plants
- Male and female
- What stands out
- Very cold hardy but lower yielding
-
Purple Passion
- Plants
- Male and female
- What stands out
- Purple spears
For the heaviest crop from the fewest plants, choose an all-male variety. Growing an early and a later variety together stretches the harvest.
Where asparagus grows best
Asparagus lives in the same spot for 15 years or more, so choose the site as carefully as you would for a fruit tree.
A bed of its own. Give it a dedicated, permanent bed, away from ground you dig every year. Don’t grow other crops among it.
Fresh ground. Never replant an old asparagus bed with new asparagus: choose fresh ground so soil-borne diseases can’t build up. Gardeners’ World also advises against ground where potatoes grew.
Shelter and frost. A warm, sheltered spot. Avoid low-lying frost pockets: a late spring frost kills spears that have come up.
Room. A mature bed is several square metres and lasts 10 to 20 years: the RHS and Gardeners’ World say up to 20, Utah State 10 to 15. RHS spaces plants 30 to 45 cm (12 to 18 in) apart in rows 45 cm (18 in) apart, staggered; US extensions use single rows 90 cm to 1.5 m (3 to 5 ft) apart.
Sun. Full sun is best: at least six hours of direct sun a day, and the University of Maryland prefers eight to ten. The RHS says asparagus tolerates dappled shade.
Mind the shade it casts. The ferns grow tall over summer, so put the bed at the north end of the plot, where they won’t shade other crops.
Too much shade shortens the harvest and cuts the crop.
- Bed life
- 10 to 20 years
- Plants per person
- 10 to 20 (Illinois)
- Yield per plant
- About 10 spears (RHS), roughly 0.35 to 0.45 kg (¾ to 1 lb) a season
- Hardiness
- Very hardy; Jersey types damaged at -34 °C (-30 °F) without snow
Soil and preparation
Asparagus needs deep, well-drained soil that doesn’t sit wet after rain. Sandy loam is ideal, but most soils work if they drain. On heavy clay, build a raised bed. Damp, poorly drained soil rots the roots.
pH. 6.5 to 7.0; it doesn’t tolerate very acid soil. Oklahoma State adds lime where soil is below pH 6.5.
Clear the weeds first. Control every perennial weed the year before planting. Once the crowns are in, you can’t dig them out without damaging the roots.
Enrich it. Dig in at least a bucketful of garden compost or well-rotted manure per square metre. Test the soil if you can: asparagus needs plenty of phosphorus to build its large root system, so add what the test recommends.
- Drainage
- Essential
- pH
- 6.5 to 7.0
- Organic matter
- A bucketful per m² before planting
Planting
Plant crowns in a trench in early spring and fill it in slowly as the shoots grow.
Order crowns early, for delivery when you are ready to plant, and plant them the day they arrive.
When to plant asparagus
Plant crowns in early spring, as soon as the soil can be worked: March or April in the UK and much of the US, early May to early June in cold regions such as Minnesota. Some all-male varieties can also be planted in autumn.
Plant on arrival. Crowns dry out quickly. If you must wait more than a few days, keep them cool and moist, refrigerated or heeled into moist soil in the shade, and never let them freeze.
From seed, sow indoors in February or outdoors in March or April, grow the plants on for a year, then move them to their final bed the following spring.
- Crowns: early spring, as soon as the soil can be worked.
- Plant them the day they arrive.
- Seed: sow in late winter or spring, plant out a year later.
How to grow asparagus from seed
Slower than crowns, but many plants for the price of a packet.
-
Sow indoors in late winter
February in the UK. Use modules or small pots of peat-free seed compost at 13 to 16 °C (55 to 61 °F), kept warm, watered and bright. Seed takes about three weeks to germinate.
-
Or sow outdoors in spring
March or April in the UK. Sow thinly, 2.5 cm (1 in) deep, in drills 30 to 45 cm (12 to 18 in) apart in a weed-free nursery bed.
-
Thin to 15 cm (6 in)
And protect the seedlings from slugs and snails. They can’t compete with weeds, so keep the bed clean.
-
Harden off indoor plants
Accustom them gradually to outdoor conditions, then move them to the nursery bed in early summer.
-
Grow them on for a year
Mulch the nursery bed with straw in late autumn to protect the young crowns over winter.
-
Move them to the permanent bed
The following spring, before growth starts, lift each young crown with as much root as you can and plant it as for a bought crown. See planting crowns.
How to plant asparagus crowns
A trench is quicker than single holes for a whole bed, and it lets you bury the crowns gradually.
-
Dig a trench
About 30 cm (12 in) wide. Depth depends on the soil: 15 to 20 cm (6 to 8 in) in heavy clay, up to 25 to 30 cm (10 to 12 in) in very sandy soil. Keep the soil you remove beside the trench.
-
Set the crowns bud side up
Space them 30 to 45 cm (12 to 18 in) apart. The RHS spreads the roots over a 10 cm (4 in) mound; UMN calls that unnecessary and lays crowns head to toe along the trench. Either way, handle the roots gently: they break easily.
-
Cover with 5 to 8 cm (2 to 3 in) of soil
Just enough to cover the crowns. Don’t let them dry out while the trench is open.
-
Water well
To settle the soil around the roots.
-
Fill the trench as the shoots grow
Spears appear in two to three weeks. Once they are sturdy and several centimetres tall, add a few more centimetres of soil, and keep going through the summer until the trench is level. Break up dry clods first: they snap the brittle shoots.
-
Mulch
5 cm (2 in) of well-rotted manure or garden compost holds moisture and keeps weeds down.
Care
Weed by hand, feed after harvest, and let the ferns grow all summer.
The ferns feed next year’s spears: look after them after the harvest ends.
Care through the years
Year one
Cut: nothing · Water: regularly all summer · Weed: by hand
Establishment only: water, weed and let every shoot become fern. See watering.
Year two
Cut: little or nothing · Feed: in spring
The sources split: some cut lightly for two to four weeks, the RHS waits another year. See harvesting.
Year three onwards: spring
Mulch: late winter · Cut: as the spears come
Weed before the spears appear, then harvest. See harvesting.
After the harvest
Feed: after harvest · Support: stake the ferns
Stop cutting in early summer and let the ferns grow. See feeding.
Autumn and winter
Cut back: yellow ferns · Mulch: 5 cm (2 in) of compost
Cut the ferns down once they yellow, then mulch. See weeding, support and cutting back.
Watering asparagus
Water new plants regularly through their first summer, and in the first two years water deeply rather than often. Good soil moisture at planting and through the summer builds the root and fern growth that next year’s spears depend on.
Once established, asparagus is drought tolerant. The RHS waters only in long dry spells. Utah State, in a dry climate, gives 2.5 to 5 cm (1 to 2 in) every other week for the first two years, then every three weeks after the third year, wetting the soil 90 to 120 cm (3 to 4 ft) deep.
After harvest matters most: new spears for next year form in mid to late summer, and water stress then gives thin spears the following spring.
Mulch to hold the moisture in.
Feeding asparagus
Asparagus needs a fair amount of food (the University of Maryland rates it medium to high), but a bed mulched with organic matter every year often needs little more.
Before planting, dig in compost or manure and any fertiliser a soil test recommends, with extra phosphorus in the trench for root growth.
Established beds. The sources differ. The RHS says most crop reliably without extra feed if mulched; if growth is poor, give a general fertiliser in early spring before the spears appear. UMN feeds only when a soil test calls for it, in early spring or after harvest. Oklahoma State feeds in early March and may repeat after harvest. Illinois feeds in spring for the first three years, then after harvest.
Test every three years or so, and don’t pile on high-phosphorus feed or manure the test doesn’t call for: phosphorus builds up in the soil.
Never use a weed-and-feed product: its herbicide can kill vegetables.
- Appetite
- Medium to high
- When
- Early spring and/or after harvest
- Every year
- A compost or manure mulch
Weeding, support and cutting back
Weeding is the job that makes or breaks a bed. Weeds compete for light, water and food, and digging them out tears the shallow roots. Pull weeds by hand rather than hoeing, weed before the spears come up in spring, and mulch to stop new ones.
Support. The ferns grow tall, and stems that snap in the wind can damage the crown. Put stakes along both sides of the row early in the season and run twine or netting between them.
Cutting back. Leave the ferns all summer: they make the food stored for next year’s spears. Cut them down once they turn yellow in autumn, to a short stub, and before any berries drop. Burning or removing old stems destroys overwintering asparagus beetles.
Female plants. Weed out the seedlings they drop, which compete with the crowns.
Asparagus in containers
It grows far better in the ground, but you can grow asparagus in a large pot if you are short of space.
Pot. At least 30 cm (1 ft) wide and deep, one crown in the centre, in good peat-free compost.
Care. Water regularly, stake it against toppling, give a balanced liquid feed through the growing season and top-dress each spring.
Expect less. A potted plant lives far shorter and crops lighter than one in a bed.
Problems
Asparagus is generally trouble free. Watch for asparagus beetle, slugs, late frost and wet soil.
Common asparagus problems
These are growing problems, not pests or diseases.
Thin, spindly spears
- Over-cutting
- Stress last summer
The crown is running out of stored food. Causes: cutting too soon or for too long, and drought, weeds, crowding or shade last summer. See harvesting for when to stop.
Spears blackened or killed in spring
- Late frost
A late frost kills spears that are already up. Avoid frost pockets when you choose the site.
Spears getting smaller through the season
- Normal
Spear size falls naturally as the harvest goes on, and tells you when to stop. See harvesting.
Roots rotting
- Wet soil
Damp, poorly drained soil rots the roots. On heavy soil, grow in a raised bed. See soil and preparation.
Weedy asparagus seedlings
- Female plants
Seed from female plants comes up in the bed. Pull the seedlings, or grow an all-male variety.
More problems with asparagus
Common pests
Asparagus beetle
Black-and-orange beetles with spotted wing covers. Adults eat the spears in spring; adults and larvae strip the ferns in summer, which weakens the plants. Pick off beetles and larvae whenever you see them, and clear old stems in autumn so they can’t overwinter.
Slugs and snails
They graze young spears and seedlings. Seedlings are most at risk, so protect them in the nursery bed.
Aphids
Green sap-suckers that stunt the ferns and cut yield and vigour. They also spread viruses, so keep them in check, especially in the establishment years.
Common diseases
Correct diagnosis matters before you act. Stressed plants suffer most, so good drainage, sensible harvesting and weed control are the best prevention.
Violet root rot
A soil-borne disease that rots the crowns. There is no cure: dig up and destroy affected plants and start a new bed on fresh ground.
Asparagus rust
More of a problem in cool, wet weather. Older varieties such as Mary Washington have limited resistance; the University of Maryland recommends all-male hybrids as more disease-resistant overall.
Fungal crown and root rots
Fern tips yellow, growing points die, and whole stems and eventually plants die, leaving thin spears. Reduce stress: over-watering, drought, over-cutting, insects and weeds all make it worse.
Viruses
Plants decline and yields fall. Aphids spread them: control aphids to prevent them.
Harvest & Use
Cut spears when they are finger-thick and a hand’s length tall, and stop in early summer.
Harvesting asparagus
When to start. Never in the year you plant. The sources differ on year two: the RHS and Gardeners’ World cut nothing until the third spring; the University of Maryland cuts lightly for three to four weeks, Illinois for up to two. From seed, add a year.
How long. The sources give different numbers of weeks. For the first cutting year: about four weeks (Utah State, Gardeners’ World) or six (RHS). For established beds: six to eight weeks (RHS, Utah State) up to eight to twelve (Oklahoma State). The rule they share: stop when most new spears are thinner than a pencil, about 1 cm (⅜ in), and in any case by early summer, so the ferns can grow.
When a spear is ready. 13 to 18 cm (5 to 7 in) tall and about finger thick. Cut every two to three days in warm weather: spears grow fast, and tall ones turn woody at the base.
How to cut. With a sharp knife, 2.5 cm (1 in) below the soil, taking care not to damage spears still underground. Or snap the spear by bending it over near the base: it breaks where the tender part ends.
White asparagus. Mound soil or straw over the bed, or cover it to keep out light, and cut each spear as it breaks the surface.
- Year one: nothing. Year two: little or nothing. Year three: a short harvest.
- Cut at 13 to 18 cm (5 to 7 in), every two to three days.
- Stop when most spears are pencil-thin.
Storing and using asparagus
Asparagus is best eaten the day you cut it. Left at room temperature it turns fibrous and loses nutrients, so refrigerate it as soon as possible, in a mesh or plastic bag.
In the fridge, spears keep three to five days at around 2 °C (35 °F) with high humidity.
Freezing. Asparagus freezes well for later in the year.
Propagation
Divide established crowns to fill gaps, or raise new plants from seed.
Propagating asparagus
Dividing crowns fills gaps or extends a bed. Do it in late winter or early spring, and no more than every three years: divided plants are slow to settle back in.
- Dig up an established crown carefully.
- Prise it apart into sections, each with several growing points. Take the strongest pieces from the edge; cut roots only where they won’t pull apart.
- Discard old, woody parts.
- Replant the sections straight away with the buds at the soil surface, as for new crowns.
From seed, see growing from seed. Open-pollinated varieties such as Mary Washington set seed; all-male hybrids set none.
More to Explore
Quick answers, guides that pair well with asparagus, and the sources behind this one.
Frequently asked questions
How long does asparagus take to grow?
From crowns, the first proper harvest comes in the third spring, with at most a light cut in the second. From seed, add a year or more.
How long does an asparagus bed last?
10 to 20 years, depending on the source, if it is well drained and kept weeded. See where it grows best.
How many asparagus plants do I need?
Illinois suggests 10 to 20 plants per person. An established plant gives about 10 spears a season.
When should I stop cutting asparagus?
When most new spears are thinner than a pencil, and by early summer. See harvesting.
Should I cut down asparagus ferns?
Only once they turn yellow in autumn. See weeding, support and cutting back.
How deep do you plant asparagus crowns?
In a trench 15 to 30 cm (6 to 12 in) deep depending on soil, covered with 5 to 8 cm (2 to 3 in) of soil at first and filled in as the shoots grow.
Can you grow asparagus in a pot?
Yes, one crown to a large pot, but it lives shorter and crops lighter than in a bed. See asparagus in containers.
Why are my asparagus spears so thin?
Usually over-cutting, or stress last summer from drought, weeds or crowding. See common problems.
Are male or female asparagus plants better?
Male: they give more spears, live longer and don’t seed into the bed. Most modern varieties are all-male.
How do you get white asparagus?
It is ordinary asparagus grown in the dark. See harvesting.
Related guides
Sources
- How to grow asparagus (opens in a new tab) Royal Horticultural Society
- Growing asparagus in home gardens (opens in a new tab) University of Minnesota Extension
- Growing asparagus in a home garden (opens in a new tab) University of Maryland Extension
- How to successfully grow asparagus in your garden (opens in a new tab) University of Illinois Extension
- Asparagus culture in the home garden (opens in a new tab) Oklahoma State University Extension
- How to grow asparagus in your garden (opens in a new tab) Utah State University Extension
- How to grow asparagus (opens in a new tab) BBC Gardeners’ World