How to Grow Asparagus in Your Garden
Guy Barter, RHS chief horticultural adviser, gives a few timely tips on how to grow asparagus.
Asparagus is
a traditional dish at Easter and although the crop is about two weeks
later than usual, British-grown spears should be on sale in Marks &
Spencer this weekend, courtesy of Wye Valley grower John Chinn.
It is extremely
easy to grow, despite the mystique that sometimes surrounds its
culture. It thrives on well-drained soil or in raised beds in a sunny
site.
Getting started
As an asparagus
bed lasts many years, it is a good idea to improve the soil with a
bucket of compost or manure every square metre. Add lime if required to
get the ideal pH of 6.5-7.5.
Choose a part
of the garden that is free of perennial weeds, and has not been cropped
with asparagus for some years. Asparagus can be grown from seed but at
this time of year it is common to plant one-year-old dormant plants,
known as crowns.
To plant, dig
out a shallow trench 30cm wide and 20cm deep. Incorporate well-rotted
manure to the base of the trench and cover the base with a 5cm layer of
excavated soil. Be sure to buy fresh crowns, as they often dry out while
on display.
Hoe a 10cm-high
ridge of soil along the centre of the trench. Place the crowns on top
of this ridge. Allow 30-45cm between each. Spread roots evenly over the
sides of the ridge, and then cover with excavated soil so that only the
tip of the crown shows.
Space rows no closer than 45cm and stagger the plants in adjacent rows. If the soil is dry, water in and mulch.
How to grow
Annual weeds
are best winkled out by hand, but can be partially prevented by covering
the beds with black plastic in winter. In late winter, mulch with
weed-free compost to discourage weeds and feed the plants.
Every spring,
apply 100g per sq m of general fertiliser such as Growmore or fish,
blood and bone, and again after harvest if growth is weak. The foliage
is essential to build up reserves for future crops. Keep it upright with
stakes and string, and free of asparagus beetle. If you allow the
foliage to yellow in autumn before cutting it down to soil level,
resources will be transferred to the roots to boost spring cropping.
Modern
cultivars are all male, as male plants produce more and better spears.
Female plants, which have berries, do arise in so-called all-male
cultivars, and account for about half the plants in non all-male
cultivars. Female plants and seedlings should be removed.
How to harvest
Don’t cut any
spears for the first two years after planting. In the third year, gather
spears from mid-April for six weeks, but in following years, if the
plants are strong, cut for eight weeks. Slice off spears with a sharp
knife just below the soil before they exceed 18cm tall. In warm weather,
this may mean cutting every few days.
Watch out for...
Slugs and
snails These browse growing tips, spoiling young spears. They are
especially active at night and after rain. Use slug control.
Asparagus
beetle Adult beetles and their larvae strip the bark and foliage. If
picking off does not resolve the problem, try a spray of natural
pyrethroid insecticide.
Frost damage
Frosts cause distorted or dead spears, often some time afterwards if the
tips are just below soil level. Cloches or fleece can hold off light
frosts.
Recommended
- 'Connover’s Colossal’ (AGM) Not all-male, but seed is cheaper.
- 'Gijnlim’ F1 AGM All-male plant, popular and reliable.
- 'Guelph Millennium’ F1 (AGM) All-male, matures later, useful in frosty gardens.
