Asparagus (Asparagus officianalis) is a hardy perennial, a member of the lily family, which will produce for over 40 years once established. The fern-like foliage grows to about 1.5m if it is not harvested as a young shoot.
This is a nutrient-rich vegetable, high in folic acid and a good source of potassium, fibre, vitamins B6, A and C and thiamine. It contains no fat, no cholesterol and is low in sodium. It tastes delicious and is often considered to be a ‘luxury’ vegetable.
It’s incredibly easy to grow in the home garden. Plenty of room and plenty of patience are the main requirements, as it takes a couple of years for an asparagus bed to become productive.
The best way to grow asparagus is by planting crowns, which are established root systems with dormant top growth. It will also grow from seed, but crowns will produce more quickly.
Because asparagus will remain productive for many years and doesn’t like to be disturbed, you must choose a position where it can be left alone. A sunny, well-drained position is essential.
Dig the soil deeply and add plenty of organic matter. Asparagus performs best when the soil pH is 6.5-7.5, so you may need to add some lime too.
Make a trench about 25cm deep, and make a little mound at the bottom of the trench. Plant the asparagus crown on this mound, spreading the roots out. Plant the crowns about 40-50cm apart, each on its own little mound. Cover the crown with 5cm of soil. Fill in the trench gradually as the shoots emerge, taking care not to cover any foliage. In a few weeks the trench will be level with the surface of the soil. Asparagus is hungry stuff, so feed it regularly during the growing season.
Now comes the hard part. For the first year, you may admire your asparagus patch, but don’t cut any spears. Ideally, you should exercise the same restraint in the second year. (If that’s impossible, take just a couple spears.) You will be rewarded with a highly productive bed thereafter. In the third year, cut the spears when they are about 15-25cm high, just below ground level, for 2-4 weeks in spring. In subsequent years, take all the finger-size spears you want for six to eight weeks. Stop cutting when the shoots become thin, and let these ones grow into ferns to feed the crowns for next year’s crop.
When the ferns start to turn yellow, cut them down and use them as mulch over winter.
The growth rate of asparagus is phenomenal. Under ideal conditions, shoots can grow 25cm in 24 hours. Once your bed is established, you will need to harvest every day.
Watch out for slugs and snails, and mulch to prevent weed growth.
If you want to grow white asparagus, then cover the shoots with something (an upturned bucket would do) to exclude sunlight.