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Asparagus Growing Guide

Asparagus Growing Guide

Ready to be seduced by the culinary crown-holder of the veg patch? Then now’s the time to plant some asparagus for many years of tender spears to come.

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Asparagus quick links

How to grow Asparagus

If there’s one vegetable that’s got the last word in culinary perfection, it’s asparagus. Smooth, flavoursome spears (shoots) of unrivalled succulence are the name of the game here, making this the kitchen garden ingredient of any chef’s preference.

Its brief season of availability has given asparagus an almost legendary status. Like the first sweet strawberries of summer, the moment that asparagus hits the shelves is eagerly anticipated. It seems that as soon as those tender spears appear, the season is almost over. 

Maybe it’s this fleeting presence of awesome taste that has given asparagus cultivation something of an air of mystery. Yet with the correct ground preparation and the completion of a few simple annual tasks, an enviable crop of spears will be yours every spring. 

Asparagus is one of a handful of perennial vegetables, sitting in the same ground for at least 10 years and often up to 20. It may seem expensive and time-consuming to begin with, but once plants are established, you can expect a cut of 10 to 20 spears per plant. Work that out over its 20-year lifespan, and you’ve got an awful lot of culinary ecstasy for the minimum of financial outlay and annual effort!

Modern, all-male F1 hybrids have done a lot to advance the attraction of asparagus to the home-grower. These vigorous varieties give a solid performance, often cropping earlier and giving bigger yields over the season. Grow them in a bed of their own where they won’t be disturbed by the comings and goings of short-lived vegetables around them. If space is at a premium, set them in among the decorative border where the post-harvest feathery foliage will form the perfect backdrop to flowering ornamentals.

Preparing the Ground for Asparagus

Meticulous ground preparation is essential if asparagus is to thrive. Unfortunately, you can’t grow asparagus in containers very successfully. If you’re wondering ‘can I grow asparagus in pots’, or ‘can I grow asparagus indoors’, it’s best not to. 

Remember that you are effectively laying the groundwork for two decades of growth, so time spent now will be repaid many times over in the years to come. There is little point rushing this job!

Asparagus prefers a free-draining but nutrient-rich soil that’s not too acidic. Aim for a pH of around 6.5-7.5, adding lime to the soil if yours is below this. Pick a position in full sun, free of frost pockets, where the plants can grow undisturbed and protected from strong winds. Some shade is tolerable, but you will get a better performance when plants can draw on good, steady sunlight. 

Bear in mind that young trees and shrubs nearby may grow larger to eventually cast shade over your asparagus crop. Plants may be grown in any plot that satisfies the above requirements, but heavy clay that hasn’t been improved in the past may prove a challenge. Consider dedicating an entire raised bed to asparagus in these circumstances, when the extra depth of soil will make all the difference.

Prepare the ground the autumn or winter before planting by digging in ample well-rotted manure or garden compost – at least a bucketful per square metre. About a week prior to planting, rake in a general-purpose organic fertiliser, such as bonemeal to give the soil a final boost for your new introductions.

How to Grow Asparagus Crowns

You can grow asparagus from seed, or by planting rootstocks (usually one year old) called ‘crowns’. It’s best not to try growing asparagus from scraps, or growing asparagus from cuttings, as you’re not guaranteed success. 

Growing from seed is cheaper than starting from crowns, but you’ll have to wait another year before you can begin harvesting. Considering a bunch of supermarket asparagus costs as much as two ready-to-plant crowns, in most circumstances the latter option is well worth the investment. Ten crowns costing about £15 should supply more than enough spears for the average family. 

A certain type of asparagus does grow wild: it’s a coastal plant that you might find in Dorset, Cornwall and Wales. Finding wild asparagus is quite rare, and it is very different to garden asparagus.

Crowns are generally planted in late March or April into prepared ground, though you can establish them in the autumn, too. Whether growing in raised beds or open ground, begin by digging out a trench 20cm deep and about 30cm wide. If your soil hasn’t been cultivated much in the past, an additional layer of compost or manure may be placed into the bottom of the trench. Cover this with a similar depth of soil to add more nutrients for the roots to grow into. 

Now add a line of compost along the bottom of your trench to create a raised mound. This will lift the buds of the crowns above the roots and help excess moisture to drain away from the delicate buds. Make sure that the roots are completely hydrated by soaking them in a bucket of water while you prepare the trench.

Set your crowns into the trench at least 30cm apart, straddling the roots either side of the raised mound. Then, fill back the soil so that the buds sit just beneath the surface. The trench can be filled in gradually during the growing season, so that by autumn, the level of soil in the trench will match that of the surrounding ground. If you intend to grow more than one trench then set these 45cm apart to give each row plenty of space.

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Growing Asparagus month-by-month

January

Check out the new-season catalogues. For trouble-free, vigorous plants pick a modern, all-male F1 hybrid asparagus such as 'Gijnlim' F1.

February

Finish preparing the ground this month to allow it enough time to settle back down before asparagus planting time in late March or April.

March

Watch out for the first delicate shoots of established plants. Keep them protected from frosts using horticultural fleece when growing asparagus in the UK.

April

Now's the time to dig an asparagus trench and set your crowns into position. Established plants will be leaping into growth.

May

This is the main cropping period for asparagus. Cut spears carefully using a sharp serrated knife, taking care not to damage surrounding shoots.

Must do this month!
June

Finish cutting spears by the end of June to enable the plant to recover for next year. Keep new plants well watered and weed-free.

July

Apply a general-purpose organic fertiliser around the base of existing plants in early July to encourage the asparagus fern foliage to grow.

August

Prop up tall asparagus foliage with a perimeter of string supported by canes. This will keep it safe from wind damage.

September

Inspect spring-planted asparagus crowns for weeds. Hand-weed to keep them clean and free from competition at this early stage.

October

Once the foliage has turned completely yellow it is time to cut it back. Leave stumps about 5cm high and then mulch around the asparagus crowns.

November

Prepare the ground for new asparagus introductions the following spring. Dig deep, incorporating plenty of organic matter, and remove all weeds.

December

Continue preparing new trenches. You can grow asparagus in raised beds in the UK: they're an excellent option in heavy soils, or to separate asparagus from other vegetables.

Caring for your Asparagus plants + problems

Each spring, just before the crowns launch intro growth, apply a generous handful of organic fertilizer around the base of each plant to give it a boost. A further feed later on in the season may be applied after the cropping period to recharge the exhausted soil. Early shoots will need some protection from late freezes to keep them in good condition – be on hand with fleece if a frost threatens.

The spear-cutting period runs from about early April to mid-June. After this, the spears should be left to grow on to unfurl into the beautiful fern-like foliage. As this continues to grow you may need to protect it from wind damage. A simple perimeter of canes and string will keep the foliage propped up and safe from snapping. 

Although the mature foliage may seem of little consequence to the food grower, it has a vital role. It traps the sun’s energy and channelling it back down to the crowns for next year’s crop. Protecting this foliage will safeguard future harvests.

How to harvest Asparagus

If you simply can’t wait to make a harvest then a few spears may be taken in the second year following planting. Cut just one or two per crown and stop here. 

It may seem like a waste to allow the remaining shoots to go uncut, but the first few years are about establishing a healthy root system. This will secure the plants for the future. Patience really will be rewarded, so bear with this establishment phase.

Of course, from the third year you can begin cutting in earnest. The first spears nudge through the ground from about early- to mid-April. Allow a cutting period of eight weeks from this point, taking the last cut in about mid-June to let the foliage develop and recharge plants. Spears may be cut once they reach about 10-15cm high – leave them to grow longer and the outer skin becomes tough and will need peeling. 

To cut, insert a knife next to the spear and cut it off 5cm below ground level so you get some pure white stem with the spear. Any sharp, serrated blade will do the job, but special asparagus knives will help. These are purpose-designed for the task, giving a good angle for a clean edge. Cut all the spears – thick and thin – because it is this harvest that stimulates new shoots to appear.

Of course, asparagus is best enjoyed as fresh as possible, and will be bursting with flavour and nutrients at the point of harvest. If you want a bigger batch of spears then a previous cut may be kept in the fridge for up to a week while more are gathered. Stand the spears upright in 2cm of cold water before placing the whole container into the fridge. 

They will also freeze very well after being cut into sections and blanched in boiling water for a couple of minutes beforehand. This gives a great excuse for growing more crowns than might otherwise be enjoyed in the short cropping season – and who could ever tire of this decadent vegetable?

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