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April 3, 2010 / Malcolm Dalebö

Growing Asparagus

Asparagus which is expensive to buy is a luxury vegetable with a relatively short harvesting period, but because it’s a perennial knowing how to grow your own delicious spears means that repeating this seasonal treat is possible for twenty years. Home produced asparagus has a unique flavour which can’t be matched by that sold in shops. Growing your own crop is an inexpensive way of adding delicate flavour to those special recipes.

This is Margaret’s’ favourite vegetable and so the decree has gone forth that we must have more asparagus. Currently asparagus takes up about half of a bed that is 19′ (3m) by 4′ (1.3m), and the plan is to remove its strawberry companions to the top allotment and reserve the whole bed for asparagus. 

Best Site and Soil Preparation for Asparagus
Asparagus will grow in a wide range of soil types and it doesn’t need to be too fertile. It pays to adhere to the following simple guidelines:
  • A well drained soil is essential, as is a deep root run.
  • Ensure all perennial weeds are eradicated during ground preparation.
  • Check the pH and lime if it is below 6. A pH of 6.5 to 7.00 is ideal.
  • Ground preparation involves digging a trench 30cm wide and 20cm deep.
  • Put well rotted manure in the bottom and cover this with 5cm of excavated soil raised in the centre to form a ridge.
We have accumulated about 10 plants over the last 3 years, both buying and inheriting the crowns. Currently we are growing Asparagus ‘Connover’s Colossal’, A. ‘Arianne’, and A. ‘Purple Pacific’. Traditional cultivars of asparagus are a mixture of both male and female. Modern all male F1 cultivars produce more spears over a longer season, but they tend to be slimmer. The variety ‘Connovers Colossal’ has thick mid-green spears of superb flavour. ‘Arianne’ and ‘Purple Pacific’ are both reliable F1 hybrids.

How to Plant Asparagus Crowns
The best time to plant seed raised one year old, or bought crowns is March/April. If you are planting inherited freebies then anytime will do!

  • Space the crowns 30-45cm apart on top of the ridge.
  • The crowns should be about 10cm deep.
  • Spread out the roots and fill in the trench to cover the crowns.
  • Keep filling in with soil as they grow leaving about 10cm of stem showing for the first few weeks then add no more soil.
However, with times being as tight as they are now, and as I am naturally mean, Margaret’s’ decree will be fulfilled by growing from seed rather than buying year old crowns. It is also more satisfying to have done it from scratch, even if it means waiting a year

How and When to Sow Asparagus Seed
Raising asparagus plants from seed to first harvest takes 3 years, but for the patient gardener it’s well worth the wait.
  • Sow under cover in large modules or 9cm pots in February.
  • Germinate the seeds in an electric propagator set at 18 degrees centigrade.
  • After germination remove the lid of the propagator and maintain a temperature of 13-16 degrees centigrade until the plants are 10-15cm tall.
  • Harden off the young plants and transfer them outside to a well drained nursery bed in June.
  • Keep weed free and watered in the first growing season.
  • Plant in them in their permanent site next April.
A bit of detective work disclosed a French variety of asparagus called ‘Precoce D’Argentuil’. Argenteuil is a traditional gourmet French Heirloom Asparagus variety developed from an 18th century asparagus variety known as Purple Dutch at Argenteuil.  This variety is the traditional French asparagus used to create the popular “white asparagus” in France through means of blanching the plants.  When un-blanched, this asparagus variety produces attractive, thick, rose-purple with an excellent flavor and tender tips.  Earlier and hardier than most asparagus varieties, seeds should ideally be sown from mid March to the end of June.
And the deciding factor is that unlike many other asparagus varieties which do not offer a decent harvest until the third year, Argenteuil will crop in the second year. So that’s it, Margaret will be harvesting the whole bed in two years time, as I will plant out the seedlings into land vacated by the strawberries after I have prepared the soil thoroughly.

With all other varieties don’t harvest any spears until three years from sowing or two years from planting one year old crowns. 

Caring for the plants
Regular plant care is fairly straight forward and not very demanding of time:
  • Keep well watered in the first year to aid establishment.
  • Keep asparagus beds weed free by hand weeding. The shallow roots are easily damaged by hoeing.
  • An annual mulch with a sandy loam or friable compost once the spears emerge is of great help in the battle to control weeds and retain moisture.
  • On windy sites the top growth can break off causing crown damage. Use canes and twine either side of the rows for support.
  • An application of general fertilizer such as ‘Growmore’ or pelleted chicken manure at a rate of 150 grammes per square metre put on as soon as growth starts in May and again at the end of harvesting is beneficial.
  • In autumn the fern (foliage) turns a lovely straw yellow. This can be appreciated for about a week then it should be cut down to 2.5cm from soil level.
The main pest to affect asparagus is the asparagus beetle. Adult asparagus beetles are up to 6mm long with yellow and black wing cases. They feed on asparagus foliage in spring. To prevent attack clear away plant debris (their hiding ground) and hand pick adult beetles and larvae.

Harvesting Asparagus Spears
Aim to cut asparagus spears when 15cm long. Resist the temptation to carry on cutting beyond the middle of the year (mid-late June), because the plants must have sufficient time to build up a store of food capable of producing a good crop next year.
  • Use a sharp knife and cut 2 to 2.5cm below soil level.
  • Discard the tough bottom end of spears which have grown much longer than 15cm, as indeed they will during hot days.
  • Special asparagus knives with serrated blades are expensive and have no impact on the ease of cutting or flavour of the crop.

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