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Growing Asparagus: A Simple Guide to Planting & Harvesting

Asparagus Close-up

Important: Unpack your asparagus straight away and, if planting cannot follow immediately, place the crowns in a box or seed tray, surround the roots with moist peat. Keep somewhere cool and light.

Initial preparation

  • A well managed Asparagus bed should remain productive for up to 20 years or longer and, therefore, it pays to prepare the ground well before planting.
  • Choose an open, sunny situation but avoid very exposed positions and frost pockets. Asparagus will grow in most deep, well drained and reasonably fertile soils. A slightly alkaline soil is preferable, with a pH value of 6.5 to 7.5. This can be easily checked using a soil test kit or pH meter. Do not plant a new Asparagus bed where a crop has been grown previously.
  • Dig the soil to a spade’s depth, forking the soil layer below, and be sure to remove all traces of perennial weeds. Incorporate a good dressing of well rotted manure or garden compost into the top 25-30cm (10-12”).
  • Ideally, this initial preparation should be undertaken some time before planting so as to allow the ground to settle.

Planting Asparagus

Plant as soon as possible after receipt but not if the soil is over wet or frosted. Handle the crowns carefully to avoid damage and do not let them dry out.

There are several methods of planting asparagus:

  • In separate rows, setting individual crowns 40-45cm (15-18”) apart with 1.2m (4’) between rows. For each row dig a trench 30cm (12”) wide and 20cm (8”) deep. Replace some of the soil to form a mound or curved ridge – 10cm (4”) high at its tallest point – at the bottom of the trench. The crowns are laid carefully on the mound with the roots spread out over the ridge and then they are covered with 5cm (2”) of fine soil which should be lightly firmed. Cover the crowns quickly to prevent drying out. The trench is filled in with soil, gradually, during the season as the shoots develop. Grown by this system, when the cropping stage is reached, a 5-8cm (2-3”) layer of soil can be mounded over the crowns in the autumn after the stems have been cut down. Repeat, as necessary, in subsequent years.
  • In 3-row beds setting the crowns 30cm (1’) each way at a planting depth of 10cm (4”). Use a trowel to dig out large enough planting holes to allow the roots to be well spaced out. If more than one bed is being planted, allow a pathway of 75-90cm (2.5-3’) between each. Close spacing of crowns, such as this, give higher yields from a given area but the spears will be of a thinner diameter. After planting, apply a top dressing of a general fertiliser, such as Growmore, at 100 grammes per square metre (3oz per sq. yard). Hoe it very lightly into the soil surface, taking care not to damage or disturb the newly planted crowns. With the separate row system, the fertiliser can be lightly raked into the soil after the trench has been dug out.

Asparagus aftercare

Keep the beds free from weeds by hand weeding or shallow hoeing – but avoid disturbing the roots which can be easily damaged. Pay particular attention to watering, as necessary in dry spells, during the season of planting when the plants are establishing themselves.
Apply slug pellets to protect the developing shoots. Do not harvest any Asparagus in the year of planting, or the following year. During this period the crowns are building up in size in order to produce heavy crops thereafter.

The first crop should be taken in the third year (that is, two years after planting). Meantime, allow the foliage (the ‘fern’) to develop naturally and, in the autumn, when it turns yellow, cut it down to within 3cm (1”) of the ground. Remove any weeds. A 5-8cm (2-3”) layer of garden compost can be applied at this stage but it is not essential.

Harvesting & subsequent attention

Depending on the season, cutting can usually start in the second half of April, continuing into June. Harvest the spears when they are 12-18cm (5-7”) above the ground, cutting them 3cm (1”) or so below the soil surface with a sharp knife (a special Asparagus knife can be used).

Take care to avoid damaging other developing shoots. In the first season of harvesting, cut for no more than 6 weeks; in subsequent years, for up to 8 weeks. Thereafter, allow the fern to grow and enable food reserves to be built up in the crowns for the following year’s crop.

If fern growth is weak, it can be encouraged by an application of Growmore at 70g per sq. metre (2oz per sq. yard). In autumn cut down the fern when it has turned yellow. If the fern is liable to be blown over in the wind, provide some support with canes and twine.

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