Grower’s Corner – asparagus
The delicately flavoured young shoots of asparagus are one of the great luxuries of the vegetable plot. Much of the mystique surrounding their cultivation is unwarranted although there are some little tips and tricks that can help you succeed with this most famous of crops.
Most modern types are all-male F1 cultivars which are more vigorous than the older, open-pollinated cultivars which were of both sexes and because they are all male, they do not self-seed. Once established they should crop for up to two decades and each crown should give nine to twelve spears per cutting season.
Choosing a site is a vital stage in getting good asparagus. You must avoid frost pockets and exposed areas and ensure you don’t plant on an old asparagus bed as diseases can live in the soil Aim for a well drained soil and if it is heavy or clayey, think about creating a raised bed. As with any long-term crop, perfect soil preparation is essential so make sure you clear all perennial weeds before cultivate to a spade’s depth, mixing in well-rotted farmyard manure which also serves to warm the bed.
Asparagus can be raised from seed or crowns. Sow seeds of an all-male F1 hybrid singly into modules in February and transplant in early June but most gardeners choose to plant crowns in March or April. To plant crowns fork over the prepared area and dig a trench a foot wide and eight inches deep, then set well-rotted manure in the bottom, covering the manure with a couple of inches of the soil you dug out using more soil to make a four inch tall ridge down the centre of the trench. Set the crowns on top, spacing them a foot to eighteen inches part and spreading the roots evenly. Fill in the trench. Leave eighteen inches between rows and stagger the plants. Water in and mulch with two inches of well-rotted manure so that the buds are just showing.
Asparagus beds must be kept weed free and the work has to be done by hand as the shallow roots are damaged by hoeing. To avoid the top growth breaking off in wind and damaging the crown, use canes and twine either side of the row for support. Take care to remove any female plants (easily identifiable, they have orange berries) and any seedlings and allow the foliage to yellow in autumn before cutting it down to an inch tall.
To harvest, cut individual spears with a sharp knife about an inch below the soil. For the best flavour, cut when they are no more than eight inches tall and in warm weather remember to harvest every two to three days. Here’s the bad news: you shouldn’t harvest at all for the first two years. In the third year, you can pick from mid-April for six weeks, and in subsequent years for eight weeks.
The main pests to affect asparagus are slugs and snails, and the asparagus beetle. To control the beetle organically, burn old stems at the end of the year to destroy overwintering beetles and hand pick the beetles and larvae from plants from late spring onwards. Alternatively you can spray with a pyrethrum derivative but be sure that if the plants are in flower, spray at dusk to avoid harming visiting bees. Thin or spindly shoots after the first two years may be due to inadequate moisture, overcropping or competition from weeds. Late frosts will cause distorted growth so protect with a double layer of fleece.
Asparagus photographs by clearly ambiguous and author’s own, used under a creative commons attribution licence