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Urban Food Garden

GROWING ASPARAGUS

Asparagus is an excellent vegetable to grow as it tastes delicious, has few pests and diseases, requires minimal work to maintain it and produces a large crop at a time of the year (early spring) when few other vegetables are ready to harvest.

Its one drawback is that it takes up to three years before it reaches its full harvest capacity.

REQUIREMENTS aND CHARACTERISTICS
  • FULL SUNLIGHT
    It can handle some shading but if it does not get at least eight hours of sunlight it tends to produce spindly shoots.
  • WELL DRAINED SOIL
  • SUITABLE FOR ALL CLIMATIC ZONES
  • REQUIRES REGULAR WATERING
  • TAKES  THREE YEARS TO REACH FULL HARVEST CAPACITY
    Up to five years if planting from seed.
  • PLANTED AS CROWNS IN WINTER
    As seeds in Spring.
PREPARING THE BED

Thoroughly weed the bed and turn it over with a fork.  Removing all the weeds is especially important if the bed has perennial invasive weeds  (such as Couch grass) as if it gets amongst the roots of the asparagus plants it is almost impossible to remove.  
Animal manure can be added at this point, but it is not necessary as the best way to fertilise young asparagus plants is to place a concentrated amount of manure directly below them when they are being planted.

Planting

Asparagus is usually planted as crowns in winter.  They can also be planted as seed in Spring, though this will lengthen the time required before harvest as seed planted asparagus will take up to five years before being able to be fully harvested.  Planting asparagus crowns is the far easier and faster way to grow asparagus.

There are two ways to plant asparagus crowns that I have used, the traditional mound method and the raised bed method.

traditional mound method
dig the trenches

Note that these are approximate sizes only.

Add manure and cover with soil

Add manure and cover
Add manure and cover
Add manure and cover

Use well-rotted cow or sheep manure. It can also be mixed with good quality compost.  Blood and bone and a small amount of rock dust can also be added.

Plant asparagus and mound

When building up the mounds make them twice as high as you want them to be, as the added soil will be loose and will settle.  The mulch is to limit weed growth while the bare mound will maximise heat absorption via the sun’s rays.  Bare soil is warmer than soil covered in mulch, that is because mulch acts as a blanket shielding the soil from the sun’s rays.  The warmer the soil in early spring the earlier the asparagus shoots will begin to grow.

Raised bed method
Digging the trenches

Raised beds are ideal for growing asparagus as they create the well drained soil that asparagus thrive in and are usually just the right width for two rows of asparagus plants.

plant and covering the asparagus crowns

As raised beds provide good drainage there is no need to create mounds as is done using the traditional mound method for planting asparagus.   Note that I normally cover my raised asparagus beds with a thick layer of mulch, but not until the young asparagus plants have established themselves.

Asparagus crowns on sale at a nursery .  They are usually available from mid-June through to early September.

Ongoing care

MANAGING WEEDS
Keep the bed weed free by regularly weeding it.   Weed suppression will be enhanced by covering the bed with a thick layer of mulch.  Mulching also reduces evaporation and adds vital organic material to the soil.   I usually add mulch when preparing the bed in mid-winter, followed by a top up mulch in mid-summer.

WATERING
Asparagus is shallow rooted, which means it can dry out quickly in warmer weather.  So, it is important to give the plants a regular water over summer.

SUPPORTING THE PLANTS
As asparagus leaves are both tall and brittle at the base they can be broken and pushed over at the slightest touch.   To avoid this I support my asparagus plants by surrounding them with stakes wrapped in twine.  I usually do this in late spring when the harvesting period is ending.   Though note that it is only necessary to support the plants if the bed is near a common thoroughfare where there is a higher risk of brushing against the leaves. 

PREPARING THE BED AT THE END OF EACH SEASON
In late Autumn the leaves will begin to turn yellow and die back, by early winter this process should be completed.  Then the bed should then be prepared for the new season.  This is done by cutting off last season’s shoots, adding fertiliser, and covering the bed with a layer of mulch.  For more information on how to do this see: PREPARING AN ASPARAGUS BED FOR SPRING.

REJUVENATING AN ASPARAGUS BED
Over time the asparagus root nodules will become increasingly denser and intertwined, to a point when it is difficult cut the asparagus shoots below the soil line.  When this happens, the bed can be rejuvenated by digging a trench through it and filling it with manure.  For information on how to do this see: REJUVENATING AN ASPARAGUS BED.

Asparagus leaves supported with stakes and twine to reduce the risk of them breaking

Harvesting asparagus

WHEN TO HARVEST
In South Eastern Australia the asparagus harvest usually begins in late winter or early spring and runs through to late Spring.  In Ballarat I begin harvesting in the first week of September.  Throughout September I harvest all the shoots, but by October I begin to let some of the thinner shoots grow on, finally finishing the season around the second week of November.  Signs that the season is coming to an end is when the bed begins to produce increased numbers of thin shoots.  It is important not to harvest shoots for too long as this will weaken the plants, which will result in a smaller harvest in the following season.

HOW TO HARVEST
Spears should be harvested when they are 12 to 18 cm high and before the tips begin to loosen (start sending out side shoots) . Once the tips loosen, the spears become tough and fibrous. To harvest spears, cut  them off about 3 to 5 cm below the ground at a slight angle.  There are specialist asparagus knives on the market, but any thin sharp knife will do the job.  Asparagus tips can also be cut or broken off at ground level, but if you harvest them this way you will miss the white section below the ground.

Harvest when 12 to 18 cm high, cut 3 to 5cm below soil level.

Pests and diseases

Asparagus is a hardy plant, there are few pests and diseases that trouble it.  The only problem I have had was caused by slugs and snails when I originally planted my first crowns.  During that first season the shoots that the young crowns produce are fewer and slower to come up. and therefore more susceptible to slug an snail attack.  Treat as you would for any slug and snail infestation.   See PEST CONTROL: Slugs & Snails Part One and PEST CONTROL: Slugs & Snails Part Two for more information on controlling slugs and snails.

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