This perennial crop takes two years to establish and has only a short cropping season, but it is well worth growing for its delicious shoots (spears)
The spears are low in calories and high in vitamin A.
The foliage can grow to 1.5 metres high with a similar spread.
For this reason you will require lots of space so great consideration should be given to where the bed is located.
One must remember that it can be / will be in this position for twenty years or more.
The key to a good crop is in the soil preparation.
Asparagus prefers a well-drained, neutral to alkaline soil, and a sunny spot.
The best crops are produced on light, sandy soils, if the soil is decidedly heavy, work in plenty of well-rotted manure.
If you have heavy soils that tends to get waterlogged, you should consider growing in a raised bed.
Asparagus is not a suitable vegetable for growing in containers.
Prior to planting out, fork out all perennial weeds (they are difficult to remove once the crop establishes), and dig in plenty of organic matter.
Apply a base dressing of a general fertiliser prior to planting.
With established plants apply a top dressing before they start into new growth and after harvest.
Once established, a bed will continue to produce crops for twenty years or more, and the size and quality of the shoots improve each year.
Plants can be raised from seed but can take three or four years to reach cropping size.
The most common method of growing asparagus is to purchase one-year-old male crowns.
Purchase all male varieties as these produce larger spears because they don’t have to expend energy producing seeds.
Asparagus seed can be sown into individual 90mm (3½”) pots and germinated at a temperature of at 13-16°C (55-60°F).
Emerging seedlings should be hardened off before being planted out.
Alternatively, purchase crowns (one-year-old plants), plant as soon as possible after delivery to prevent the fleshy roots from drying out.
New bed culture
Week 40 (the previous year) to Week 15:
Select a site protected from north easterly winds.
Prepare a 1200mm (4ft) wide bed by digging in well rotted farmyard manure or homemade compost into the topsoil.
A week or so before planting,rake in a general fertiliser at a rate of 90g/sq m (3oz) over the area.
Plant out crowns.
Asparagus plants can be either all-male F1 hybrids or a mix of male and female plants.
Hybrids are more vigorous and are generally higher-yielding.
Dig a trench 300mm (12”) wide and 250mm (10”) deep.
Form a 100mm (4”) high ridge of good soil along the base of the trench, and plant one year-old crowns, 300mm (12”) apart, spreading the roots evenly on either side of the ridge.
Cover the crowns with 50mm (2”) of soil and gently firm and water them in.
During the growing season, continue to cover the crowns until the natural soil level is reached and ensure plants are kept well watered.
Plant out Asparagus that has been raised from seed 50mm (2") deep.
The first asparagus spears can be cut two years after planting.
In the first year, only crop for a maximum of six weeks but in subsequent years this can be extended to eight weeks.
Established bed culture
Week 16 to 18:
To ensure long-stemmed blanched spears ridge up the rows with a draw hoe, and top-dress with a general fertiliser at the rate of 60gms (2oz.) per sq metre.
Cropping can usually begin in the second year after planting.
Cut the shoots when they are 100-150mm (4”-6”) tall.
Make the cuts approximately 50mm (2") below ground level, taking care not to damage any other stems.
Asparagus Spears (shoots)
With relatively new plants, restrict cutting to about four spears per plant until the bed is firmly established (usually three years or more from planting)
However, with long established plants. harvest all the spears, including thin and bent shoots, as this will help to promote new growth.
If they cannot be used immediately, stand them in jars of fresh water to prevent their rapid deterioration.
After mid-June leave any further stems to develop until autumn.
Keep beds free from weeds.
Summer hoeing will help to suppress annual weeds, and also prevents surface compaction of the soil.
Water beds liberally throughout summer.
Watch for signs of the orange and black asparagus beetle and their grubs otherwise they may strip the fern / foliage.
Apply a nitrogen fertilizer such as nitro-chalk at a rate of 30 gm (1 oz) per sq m.
Apply a 50-70mm (2"-3") layer of well-rotted manure, which will also suppress weeds.
Remove unripe berries to prevent a mass of unwanted seedlings next year.
Berry formation also diverts energy from growth.
Tie the fern into canes with soft twine or twist ties if the plants are exposed to strong winds.
Week 36 onwards:
When the ferny foliage begins to change colour, it should be cut back to within 25mm (1”) of the ground, and burned, again to prevent berries of female plants producing inferior seedlings.
Crowns may be forced to extend the season or for exhibition purposes by lifting four-year-old or older crowns and placing them under the greenhouse staging.
Cover the crowns with 50mm (2”) of potting compost.
Keep the crowns at a temperature of 16C (60 F), and in moist soil.
After forcing, crowns should be discarded, but may be replanted in the permanent bed after harvesting.
They generally take a year or two to recover and produce worthwhile crops again.