Asparagus plants can remain productive for up to 20 years, so it’s worthwhile spending time on preparing the bed to give them a flying start in life. If you can, start in autumn by digging over thoroughly, mixing in plenty of well-rotted farmyard manure, and removing all perennial weeds. A week or so before planting, scatter some general fertiliser granules over the area (about 90g/ sq m is ideal) and fork in, before raking the ground level.
You will need about an hour to plant 10 crowns. Make a straight trench, 30cm wide by 20cm deep, and then pour soil down the length of the trench to make a 10cm high mound. Next, carefully take your asparagus crowns and sit them on top of the mound, spreading the roots out either side – plant crowns 30cm apart and then cover with about 5cm of soil, which has been sifted through a riddle or sieve. Cover the plants with more sifted soil as the stems grow, aiming to completely fill the trench by autumn. Subsequent rows should be spaced 30cm apart.
Water newly planted crowns thoroughly and keep damp during dry weather. Succulent spears may appear soon after
planting, but avoid the temptation to harvest them or you’ll weaken the crowns. During their first two years of growth, plants should be left to form lots of ferny foliage – cut down the stems in autumn, leaving 5cm stumps above the ground. To prevent competition, keep beds free of weeds.
Most plants are ready to be picked two years after planting, although several modern varieties have been bred for earlier cropping. To harvest spears, wait until they’re about 12cm long and remove them with a serrated knife, cutting them off 7cm beneath the soil. Stop harvesting in mid-June to allow the plant to build up its energy for next year, and give plants an extra boost by feeding with a general fertiliser.