Few crops reward patience quite like asparagus. Plant it once and, after a couple of years of holding back, you can look forward to fresh spears every spring for up to 20 years. It is a genuine perennial: slow to get going, but wonderfully generous for decades once it has settled in.
This guide walks you through how to grow asparagus from start to finish, whether you are sowing seed under cover in the greenhouse or planting crowns out in a raised bed. We will cover sowing, planting, harvesting, the pests to watch for, and a few recipes to put your spears to good use.
One quick word on timing first. The UK asparagus season is short and precious, running from around mid-April to late June. You will not harvest anything in the first year or two, but everything you do early on sets up those reliable spring harvests for years to come.
Starting asparagus in the greenhouse
A greenhouse gives asparagus a gentle, controlled start in life. Sowing under cover in late winter lets you raise strong young plants well before the soil outside has warmed up, and it keeps tender seedlings safe from late frosts and hungry slugs. Think of the greenhouse as a nursery: you raise the plants here, then move them outside to their permanent home. If you are tight on space, even a compact patio greenhouse is enough to get a batch of seedlings going.
Growing asparagus from seed
Growing asparagus from seed is the cheaper route, and a single packet can give you a whole bed of plants. The trade-off is time: you will wait three years before your first proper harvest, rather than two from crowns.
Sow seeds in February at a temperature of around 13 to 16°C (55 to 61°F). Fill seed trays or small pots with moist, peat-free seed compost and sow one seed into each, roughly 1cm deep (or a finger tip).
Top tip: Soaking the seed in water for a day or two beforehand helps soften the coat and speed things along. Germination is naturally slow and can take three to four weeks. A heated propagator makes this far more reliable in a cold greenhouse.
Keep the pots somewhere bright, warm and well watered. Greenhouse shelving or a seedrack lifts your trays off a cold floor and keeps them close to the light, which young asparagus seedlings need plenty of. Keep the compost just moist and never waterlogged, since asparagus hates sitting wet.
When to plant out
Harden the young plants off gradually so they get used to outdoor conditions. Plant them into their final bed in early June, let them grow on for their first year, then lift and replant them at their final spacing the following March.
Growing asparagus outside or in raised beds (from seed and crowns)
If there is one crop that loves a raised bed, it is asparagus. Raised beds give the sharp drainage asparagus depends on, which matters enormously on heavy or clay soil where wet roots quickly rot. They also make it easy to give this permanent crop its own dedicated space, free from competition, and to keep the bed weed-free. A metal raised bed will not rot or harbour pests the way timber can, which suits a crop that stays put for two decades.
When to sow and plant
You can establish a raised bed of asparagus from either seed or crowns. Sow seed outdoors in March or April once the soil is workable, or start it earlier under cover (see above). Plant dormant crowns in March or April, as soon as they arrive. Germination outdoors is slow, often three to four weeks, so do not panic if nothing shows for a while. Our monthly seed sowing guide is handy for keeping the rest of your veg patch on track at the same time.
Which asparagus variety is best?
Where to position your bed
Pick a warm, sheltered, sunny spot. Asparagus does best in full sun but will tolerate light, dappled shade. Avoid frost pockets, since late frosts can damage emerging spears, and steer clear of very windy sites that could snap the tall summer ferns.
Watering, soil, spacing and seed arrangement
Soil: asparagus wants rich, free-draining soil with plenty of organic matter. Before planting, weed the bed thoroughly and dig in a generous bucketful of well-rotted manure or compost per square metre. Do not start a new bed where asparagus has grown before, to avoid any build-up of soil-borne disease.
Spacing and arrangement: when sowing seed, sow thinly in a drill 2.5cm deep with rows 30 to 45cm apart, then thin the seedlings to 15cm apart and grow them on for a year before moving them to their final positions.
Growing Asparagus Crowns
Watering: water regularly through the first year, then only in dry spells once plants are established. Mulch the bed with a 5cm layer of well-rotted compost each late winter to lock in moisture and suppress weeds, and weed by hand rather than with a hoe to protect the shallow roots. Our month-by-month raised bed guide sets out the seasonal jobs in more detail.
Asparagus companion plants
A little companion planting helps an asparagus bed thrive. The classic partner is the tomato: tomatoes are thought to deter asparagus beetle, while asparagus helps repel the root nematodes that attack tomatoes.
Basil and parsley make excellent neighbours too, alongside dill, coriander and marigolds, which all draw in beneficial insects or distract pests. Strawberries work nicely as low ground cover at the edge of the bed.
Just as useful is knowing what to keep away.
Top Tip: Avoid planting onions, garlic, leeks and other alliums near asparagus, as they compete hard for the same nutrients and can stunt your spears. Keep potatoes and carrots out of the bed as well, since their roots jostle with the asparagus crowns, and skip fennel, which sits poorly with most vegetables.
Growing asparagus in a 6x4 raised bed
When and how to harvest
Harvesting from a raised bed is exactly the same as harvesting from open ground. Wait two years after planting crowns (three from seed), then from the third year cut spears from mid-April for six weeks, building up to eight weeks in later years. Slice each spear with a sharp knife 2.5cm below the surface when it is finger-thick and no more than 18cm tall, harvesting every couple of days in warm weather. Stop around late June, then let the ferns grow up to feed the crowns for next year. Supporting the ferns with stakes and twine stops them snapping in summer winds.
Cooking with asparagus
Asparagus is at its best eaten within a day or two of cutting, when it is sweet and tender, and a quick sizzle in butter with a little salt is hard to beat. For something more adventurous, chef Gill Meller has shared several spring recipes on the Rhino blog that make the most of a fresh harvest:
If you do need to keep spears for a few days, trim the ends and stand them upright in about 2cm of water in the fridge, changing the water daily, just as you would a bunch of flowers.