How to Grow Asparagus

Asparagus officinalis · Also called: Garden asparagus, Sparrow grass, Espárrago, Spargel, Asperge, Shatavari plant, Aspargo, Asparago

A single asparagus spear with a tight purple-green tip pushing up through cracked bare soil, surrounded by the pale dry stubs of the previous season's ferns.

Photo: Vmenkov, CC BY-SA 3.0 (Wikimedia Commons)

Asparagus is one of very few vegetables that is planted once and cut for fifteen or twenty years. That is its whole attraction and its whole difficulty: it costs two years of patience before it pays anything, and then it pays every spring for a very long time. China grows most of the world's crop, Peru is the largest exporter and built a serious export industry on it, and Mexico, Germany, Spain, Italy, the United States and Japan all produce. It sells at a high price into city and export markets, it tolerates salty ground better than most vegetables, and once established it asks less of a grower each year than almost any other high-value crop.

Growing Asparagus, Stage by Stage

1. Get the land ready — Choose deep well-drained ground, clear every perennial weed, and dig a proper trench.
2. Choose your crowns or planting material — Buy one-year-old crowns of an all-male kind from a clean nursery.
3. Plant the crowns — Spread the roots over a low ridge in the bottom of the trench and fill the trench in slowly over the season.
4. Water — Water steadily in the first two years, then during the cutting season and while the ferns are growing.
5. Weeds and feeding — Keep weeds out by hand and by mulch, and feed the bed after cutting stops rather than before.
6. The fern year and the rest period — After cutting stops, let the ferns grow all season untouched, because they are next year's crop.
7. Watch for trouble — Crown rot ends a bed, rust ends a fern season, and the beetle eats the ferns that feed next year.
8. Harvest the spears — Cut spears daily while the tips are still tight, and stop after six to eight weeks whatever the bed is doing.
9. Keep, store and sell — Cool the spears at once, stand them upright in a little water, and sell within two or three days.

Common Problems & Troubleshooting

If you see: A bed that yielded well for a few years and now sends up thin, few and weak spears every spring.

It likely means: It was cut for too many weeks. Every spear cut is food the crown does not get, and a bed cut past its season starves a little more each year until it stops.

Do this: Stop cutting after six to eight weeks, and after two weeks in the second year, whatever is still coming.

If you see: Patches of the bed where spears come up few, thin and yellowish, ferns yellow early, and a dug-up crown shows reddish-brown streaks and rotted roots.

It likely means: Crown and root rot, the disease that ends asparagus beds. It lives in the soil and is worse in wet ground and in beds that have been dug or damaged.

Do this: Never plant asparagus where asparagus has grown before, since the fungus stays in that soil.

If you see: Spears whose tips have opened out into little branches before you got to them, with the stem starting to go woody.

It likely means: They were left too long. In warm weather a spear grows several centimetres a day and passes from perfect to unsaleable within a day or two.

Do this: Cut the bed every day in warm weather, and twice a day at the peak.

If you see: A bed three or four years old so full of grass and perennial weeds that you can barely see the rows, with yields falling.

It likely means: Weeds were not cleared before planting, or were allowed in afterwards. A perennial bed cannot be dug over, so weeds that establish are very hard to remove.

Do this: Clear every perennial weed and grass root before planting, which is the only easy time.

If you see: Orange-brown powdery spots appearing along the fern stems in the middle of the season, turning dark brown or black later, with the ferns yellowing early.

It likely means: Asparagus rust. It attacks the ferns, which means it attacks next year's crop rather than this year's.

Do this: Cut and carry away all dead fern material at the end of every season, since the fungus survives on it.

If you see: Small dark beetles with pale square markings on the ferns, grey soft grubs beside them, and stems chewed bare in patches.

It likely means: Asparagus beetle. It eats the ferns, and ferns are what feed the crown for next year.

Do this: Pick beetles and grubs off by hand in the morning when they are slow, which is usually enough on a small bed.

If you see: Spears arriving at market curved upward at the tip and no longer straight, although they were cut straight.

It likely means: They were laid flat after cutting. A cut asparagus spear is still alive and still trying to grow upward, and it bends within hours.

Do this: Stand cut spears upright with their ends in a little clean water immediately.

Yield & Market Value

Growing the crop is only part of the job. The last part is knowing what a normal harvest looks like where you are, and knowing what your spears are worth before you agree a price with anybody.

Remember It This Way

If you forget every other page of this guide, keep these lines. They are the whole crop, in order, short enough to carry in your head.

One planting, twenty years. Choose the ground like an orchard.
Clear every perennial weed first. You never dig this bed again.
All-male crowns. Female plants waste themselves on berries.
Trench, ridge, roots spread, cover a little and fill in slowly.
Cut nothing the first year. Two weeks the second.
Then six to eight weeks a year, and stop on the date.
Thin spears mean stop sooner. The crown is telling you.
Cut daily. A tight tip becomes an open one overnight.
The ferns are next year's crop. Never touch them while green.
Cool at once and stand them upright, or they bend.

Test Yourself: Identification

What does a spear look like when it is ready to cut?

The tip has opened out into little branches. Can I still cut it?

Why is the whole field allowed to grow into tall feathery bushes?

Honest Limits of This Guide

Timings are given as a season and in weeks from the start of cutting rather than in named months, because asparagus is a spring crop in temperate countries and a cool-season crop where it is grown in the subtropics. Count from when your own bed first pushes spears.
Yield figures depend heavily on the age of the bed, and a second-year bed and a fifth-year bed differ by several times. Any figure quoted without the bed's age attached is not comparable to another.
White asparagus is mentioned here but not taught in full. It is the same plant grown under ridged soil or plastic and cut before it sees daylight, and it is worth doing only where a buyer genuinely pays more for it, which is true in some markets and not in others.
This guide names no chemical treatments. The two things that really end asparagus beds, crown rot and weeds, are decided by site choice, drainage and the work done before planting rather than by anything applied afterwards.

Sources

GBIF Backbone Taxonomy species-match record for Asparagus officinalis L. — Global Biodiversity Information Facility (GBIF), Copenhagen (source)
EPPO Global Database — Asparagus officinalis (EPPO code ASPOF) — European and Mediterranean Plant Protection Organization (EPPO), Paris (source)
FAOSTAT crops and livestock products — production and trade data for asparagus — Food and Agriculture Organization of the United Nations (FAO), Rome (source)
Asparagus officinalis (asparagus) — CABI Compendium datasheet — CABI, Wallingford (source)

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