How to Grow Asparagus

Asparagus (Latin name Asparagus officinalis) is a hardy perennial with all parts being edible. We eat the stalks which are know as spears. When sown from seed they take 3 years to produce a crop, two years when grown from a 1 year old crown. Each plant will produce approximately 25 spears each year. Asparagus plants will continue to crop for around 20 to 25 years. If you want to know some interesting facts about asparagus click here.

Cultivation of asparagus is relatively simple if you follow some basic rules. Do that and you will have a delicious annual crop of spears which may well outlive you!
 

How to Grow Asparagus - Site and Soil

They need a well drained soil that still holds water and they do not like heavy clay or acidic soils. The best soils will have a pH of 6.5 to 7.5. A late frost can damage the crop severely so avoid planting in frost pockets. Asparagus can be grown in partial shade with success but the best results are achieved when they are grown in full sun.

Seed or Crowns?

Asparagus crown

Asparagus can be grown from seed or one year old plants (known as crowns) can be bought from your local garden centre or nursery. Growing from seed is the cheapest method but it is more time-consuming and it will take you an extra year to get a crop. On the other hand, asparagus grown form seed will transplant better with an almost zero failure rate. With crowns you can expect around a 10% failure rate.

Asparagus can be grown from seed or one year old plants (known as crowns) can be bought from your local garden centre or nursery. Growing from seed is the cheapest method but it is more time-consuming and it will take you an extra year to get a crop.

This article assumes you have one year old crowns either bought or grown from seed. If you wish to grow asparagus from seed click here and then return to this point.
 

How to Grow Asparagus - Planting

Prepare the planting area well in advance, autumn is a good time. Dig over the entire area to a spade's depth removing all traces of weeds. If the soil is not well-drained then add some grit or lots of compost.

The crowns should be planted in mid-April. The diagram below shows the best way to plant an asparagus bed. Any planting plan will be OK though as long as the plants are 45cm (1ft 6in) apart.

For each row dig out a trench 25cm (10in) deep by 30cm (1ft) wide. Fill the bottom 8cm (3in) with well-rotted compost then cover with the soil forming a ridge. The picture on the left shows a lengthways view of the trench with the ridge.

Place crown on the top of the ridge and drape the roots either side. Cover with crumbly soil so that the crown top is 8cm (3in) below the surface. Asparagus roots spread a long way so leave free an area of 75cm (2ft 6in) around the edge of planted bed. Click the picture on the right (planting asparagus) to enlarge it.

How to Grow Asparagus - General Care

Feed with a general purpose fertiliser in mid-March and then again mid autumn. The asparagus bed should be kept weed free and because they are shallow rooted it's best not to use a hoe. Hand weeding is best. With this in mind it may be best to mulch the area to stop weeds.

As they grow, the plants will need some form of support to avoid wind damage. Stakes along the rows of plants with two tiers of string will be fine.

In autumn when the foliage turns yellow or brown cut the plant down to 5cm (2in) above ground level.

Harvest Asparagus

Don't harvest asparagus for the first two years after the crowns are planted. This will allow a good root system to develop. Opinions vary but normally asparagus is harvested when it is about 15cm (6in) tall. Any taller than this and the skin will start to thicken and it will need to be peeled before eating.
 

Cut off the shoots with a sharp knife about 2cm (1in) below the soil surface. You'll need to harvest every 3 days or so because asparagus can grow very, very quickly. In warm and moist soil they can grow 15cm (6in) in a day, so daily harvesting may be required when the growing conditions are ideal. Harvest for 8 weeks and then stop. The remaining shoots will enable the asparagus plant to build up the roots.

Eat as soon as possible after harvesting . Asparagus freeze very well.
 

Asparagus Pests and Diseases

Slugs can be a problem when they eat the young asparagus shoots. For more details on how to control slugs click here.

The other pest that sometimes attacks the foliage is the Asparagus Beetle. The little bugs are about 8mm long, and are black with yellow spots on them. They can be picked off individually in most cases, but if they become too numerous, spray at weekly intervals with derris. These pests over-winter in the soil and debris around the plants so burn any foliage which is cut down in autumn.

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