How to Grow Asparagus: Plant Once, Harvest for Forever!

There’s a gourmet vegetable you can plant once, then harvest for 20 years or more; that’s among the very first vegetables of spring; and is an absolute luxury. If there’s one vegetable that rewards patience - and then keeps on rewarding you - it’s got to be asparagus!

Preparing an Asparagus Bed

Asparagus is very easy to grow, but absolutely insists on one thing, and that’s a weed-free start. These are delicate, dainty plants, at least early on in their life, so the last thing they need is to be swamped by unruly weeds.

Perennial weeds especially are the real enemy here – things like couch grass or bindweed that creep underground. Asparagus will be in the ground for potentially two decades or more, so it pays to take the time sift through and fish out any perennial weed roots you can because once asparagus is established, digging out weeds becomes a much trickier task. Use a fork to lever out as much root as you possibly can.

While asparagus can tolerate a little shade for part of the day, full, glorious sunshine will produce the best spears, more of them, and an earlier harvest.

Asparagus loves good drainage, and it’s often grown commercially in areas with naturally sandy soil. If your garden has sandy soil and you often have the problem of it drying out too quickly for some crops, it might just be perfect for asparagus! Asparagus farms often grow them raised up on mounds with trenches either side to help maximise drainage and get the very best results.

My soil can get pretty soggy in winter, which could risk rotting the crowns (where the roots come from), so I’m growing my asparagus in a raised bed to improve drainage. I’ve filled my beds with a mix of all-purpose potting mix and a sandier blend of bagged topsoil to help with that. The raised bed also encourages the soil to warm up earlier in spring, meaning spears are produced just that little bit sooner.

Add plenty of well-rotted compost to the bed before planting to improve fertility. Adding plenty of organic matter and treating the soil now is one those cases of where a little extra effort early on should pay dividends for years.

How to Plant Asparagus

The quickest route to harvest is planting roots or ‘crowns’. These are usually one year old, which gives a head start of at least one year over sowing seeds (though we’ll also be doing that shortly in case you’d prefer to start them off that way, as it is much cheaper).

Crowns can be planted anytime the soil is workable in winter or spring. Dig out a shallow planting hole for each crown, roughly 4-6in (10-15cm) deep. Each hole needs to be wide enough to easily accommodates the roots – we don’t want them bending back on themselves. These guys need to stretch their legs and get comfy!

Space each plant at least 18in (45cm) apart. In a small space you can plant them evenly spaced in both directions, but if you want to grow longer rows of asparagus you might find it easier to space the rows slightly further apart, say 2-3ft (60-90cm), but then setting the crowns a bit closer within the row, about 12in (30cm) apart. That wider spacing would then allow you to get in between plants more easily for weeding and harvesting.

Make sure the bottom of each planting hole is nice and level, and then create a small mound in the middle to help the plant shed water. Lay the crown on top and spread the roots out carefully, a bit like the spokes of a wheel, making sure they don’t curl back on themselves. Cover the crown back over with your prepared soil.

If you’re planting in winter you might want to mark the position of each crown with a bamboo cane or similar, just so you don’t forget where they are and accidently dig them up or – worse still – hoe them off just as they’re pushing through!

Water plants in to settle the soil around the roots. Asparagus is pretty self-reliant once established, but keep them watered in dry weather while they’re settling in. Once the young shoots push though, mulch the plants with organic matter such as compost or a few layers of dried grass clippings to provide extra nourishment, moisture retention and weed suppression, all in one.

Best Asparagus Varieties Grow

Because asparagus stays put for so many years, choosing the right variety now really matters. For me that means picking a hybrid variety that’s been bred to give thicker spears, and plenty of them! I’ve chosen a variety called ‘Gijnlim’, which is an all-male variety. Other all-male hybrid varieties include Backlim, Guelph Millennium, Jersey Knight, Mondo, or Walker Deluxe.

All-male varieties have the advantage of being generally more vigorous. Because they don’t need produce berries, all of the plant’s energy will go into recharging the crown each season – which means stronger plants and the best possible harvest, spring after spring.

That said, the bright red berries are very attractive, so if you’re looking for something that adds a little colour in autumn, a traditional variety may work for you.

While the asparagus plants are small in their first year you can make the most of the unused space around them by planting crops that won’t compete for space, such as spinach.

Growing Asparagus from Seed

Growing asparagus from seed takes longer, but it is wonderfully economical and deeply satisfying! It’s a great way to start off a much bigger asparagus patch without breaking the budget. And for such a frothy, delicate-looking plant, they’re very easy to sow and grow.

Sow anytime from the very end of winter and on into spring. I like to sow into plug trays, but you could use small pots. Fill them with all-purpose potting mix, and sow one seed per plug or pot, then cover them over.

Asparagus seeds can be a bit slow to germinate – up to a couple of weeks – but you can speed them along by bringing trays inside to germinate, avoiding the drop in temperature at night.

Once seedlings appear, take them back outside or into a greenhouse or cold frame. Once the roots fill their plugs, carefully remove the little seedlings and pot them on into larger pots to give them room to grow. And once they’ve filled those pots, they can be planted outside, usually in early summer, setting plants at exactly the same spacings as for one-year-old crowns.

However you decide to start them, you’ll be creating a patch that could feed you for decades, and at a time of year when there’s little else to eat from the garden – a real plant once, harvest forever crop!

Growing Asparagus

In spring, you’ll see the first asparagus spears starting to push through – a thrilling portent of things to come! These spears are actually the new shoots of the season. Left alone, they’ll grow into tall, airy, fern-like foliage, which is not just rather pretty, but incredibly important. They act like solar panels, catching the sun’s energy and feeding it back into the crown underground.

So patience really matters the first few years after planting, because we want the crown beneath the soil surface to get bigger and bulk out. Think of it as investment gradually accruing interest – if we allow it to keep soaking up all that solar energy now, we’ll get bigger, better harvests later down the line.

So in the first two full years after planting we won’t be taking any harvests. We’re building strength underground. Then in the third year we can start to cut and enjoy a few spears, but only over a four-week period so we’re not exhausting the still relatively young plants. But then, from year four, that harvest window blows wide open to two full months, usually starting sometime in spring and finishing by around the summer solstice.

I know it sounds like a painfully long wait, but once harvests begin, they will keep coming back every single year – so it’s well worth it.

Once asparagus is established, it’s astonishingly low-maintenance. Because the foliage is airy rather than lush, it doesn’t need huge amounts of watering – just water during very dry spells and, of course, while plants are getting established. The main job is to keep on top of weeds. A mulch of compost every spring will help to feed plants beautifully – they shouldn’t need any other fertiliser.

The only real pest of asparagus is the aptly named asparagus beetle, which can nibble leaves and spears, while laying little rows of eggs. But honestly, damage is usually more cosmetic than serious, and asparagus beetles have plenty of natural predators including ladybirds and lacewings, which love eating their eggs (and who doesn’t love eggs for breakfast!). But if you do happen to see any of the beetles, perhaps just pick them off by hand and drop them into a bucket of soapy water to keep problems at a minimum.

How to Harvest Asparagus

Asparagus harvesting time really does feel special. Cut or simply snap off spears when they’re about finger thickness, and while the tips are still tightly closed. During warm weather you may need to harvest every day because new spears appear quickly – a delicious problem to have, right?! Gluts can always be blanched then frozen, pickled or even turned into a delicious luxury stock.

Don’t be tempted to push it too far. Stop harvesting once your harvest window’s closed (that’s two months of picking for established beds) then let the remaining spears grow on to produce those stunning feathery ferns. It’s a beautiful rhythm… not so much eat, sleep, rave, repeat, as eat, rest, recharge, repeat – year after year.

The tall, feathery, flamboyant fronds make asparagus fab as a temporary seasonal screen. They can flop over, however especially after rain, so to stop them getting in the way of paths or other crops you could drive in a stake at each end of the row and run string either side to keep the fronds contained between the strands.

By mid-autumn the ferns naturally yellow and start dying back. Leave them till they’ve fully died off so they have as much time as possible to recharge the crown for next year’s crop, then cut stems down close to ground level. Remove any weeds then, at any point over winter or early spring, add that top-up layer of mulch to nourish the soil. And that’s pretty much all the work required for the year.

Fresh asparagus is in a league of its own, it really is! Steam it, lightly grill it, toss it into pasta, or simply drizzle with a good, extra virgin olive oil and a pinch of sea salt. Picked minutes before cooking, it’s sweet, delicate, and completely unlike anything from the supermarket. And knowing those spears will return every spring with barely any effort? That’s gardening at its very best!

Are you starting an asparagus bed this year, or maybe you’re already enjoying those first spring spears? Let me know in the comments below!

Spring’s only getting started, so if you haven’t yet planned out your garden for this season, there’s still time. Why not take advantage of a free, 7 day trial of our Garden Planner to make it happen?

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