Asparagus, a worthwhile long-term project

Late winter/early spring is the time of year to plant Asparagus crowns.  When do you cut the spears?  What maintenance do they need?  Should you only get male Asparagus?  Here are some of the answers.

My fern forest at the end of Year 3

Overview

First cultivated by the ancient Greeks, Asparagus is a member of the Lily family, originating from eastern Mediterranean coastal areas.  Its shoots (called spears) come in green, white or purple, but that does not mean there are three Asparagus varieties.  White Asparagus, a sought after delicacy in Europe, is simply green Asparagus grown in the dark.  Purple Asparagus, on the other hand, is a separate variety described as sweeter and softer.

Growing Asparagus is a very worthwhile long-term project that provides little return in the first few years, but that can produce a delicious crop for the two decades thereafter.

What to buy if you want to grow Asparagus?

Some people buy Asparagus seeds.  Sow the seeds in a seed tray with large individual sections, keep watered and they will come up, because Asparagus seeds easily germinate.  But in their first year they won't look like to photo below.  Keep the small seedlings in the tray for the first year or plant them out in nice tasty soil, look after them and at the end of Year 1 the foliage will die off and leave you with what most people buy, that is one year old root systems called crowns.

The advantage of buying crowns over seed is that you have gained a year, but crowns are a lot dearer than seed.  If you buy crowns, make sure that they are fresh and firm.  Plant them immediately if possible, or wrap them in slightly damps sphagnum moss until you can do so. 

Why the focus on male/female?

Asparagus plants are either male or female.  Both male and female plants flower when they are mature, but from there on female plants focus on producing seed, whereas male plants use all that energy to produce spears.  The result is that male plants have much thicker spears than female plants.

The big question for most people growing Asparagus is therefore 'how do I make sure all my plants are male?'  The answer to that question is not so easy.

The seeds all look the same.  The crowns all look the same.  Well, some suggest you buy the fattest crowns if you have the choice, but there is no guarantee.  You may also not see much difference when spears come up in the first year.  Stalks may be thin because the crown is still establishing itself.

You really only know for certain that an Asparagus plant is female when the mature plant produces seeds, that are green at first, and then turn red in Autumn, and that may be in Year 3 of the life of the plant.  By the way, these berries are poisonous.

Yep, this is a female plant

For home growers it may not matter much if some spears are a bit thinner and somewhat lower quality than others, but commercial growers literally can not afford to find at the end of Year 3 that half their plants are female.  This is why for many centuries seed-cultivators have tried to create Asparagus varieties that produce many more male than female plants, with considerable success.

High-yielding hybrids such as 'Jersey Knight' and 'Jersey Giant' produce a very high percentage of male plants.  However, it is very likely that some of the old fashioned heirloom varieties such as 'Mary Washington' have a better taste.

  

Planting Asparagus

Carefully choose where your Asparagus plants are going to be, because ideally they will be in that spot for at least the next 15 years.  You can move mature Asparagus crowns in mid-winter, but this will diminish yield for at least the following season.

Asparagus is a heavy feeder that likes a sunny position in rich non-clay well-drained deep soil, therefore a raised bed with plenty of compost is an ideal environment.  Recommended pH is 6.5 to 7.5, so that is higher than many other food garden crops. It is because Asparagus originally came from a maritime environment.

Plant asparagus plants late winter to early spring, before growth occurs from the crown. Dig a hole about 15 cm deep. Place a small mound of earth in the hole; then set the plant on the mound so that the roots hang down and are evenly spread out in the hole. 

Cover the crown with 5 cm of topsoil  and water well to get rid of air pockets.  As spears begin to form, add more and more soil until the hole is completely filled. The top of the crown should be 10 to 13 cm below the soil surface. 

Between-row spacing should be around 80 cms, in-row spacing around 40 cms.

If your aim is to produce white asparagus, start with a deeper trench (around 20 cms deep) and keep adding soil on top, making sure that all the time just the tips of spears are above soil level.

When to cut spears?

I bought one year old crowns two years ago.  We have eaten the odd spear, but I killed one plant by cutting too many spears.  My plants are at the end of Year 3.  What can I expect from here on?

Year 1: the plant grows from seed and forms a crown.  During the year you do not cut any foliage because the foliage feeds the crown and you want a strong crown to develop.  At the end of Year 1 the foliage dies, you cut it off, dig up the crown and plant it in its permanent position.

Year 2: spears will come up, get branches and fern-like foliage will form, same as in Year 1, but taller and thicker.  If you cut spears this year you decrease the growth of the crown or worse cause stress.  Yep, that happened with one of mine and it died!

Year 3: in Spring harvest one spear per plant (if you can't stop yourself) and let the rest grow.  Stalks can become 1.5 metre high (see photo above).

Year 4: is when finally a full cutting season of 6 - 10 weeks is permitted. Pick regularly to encourage and increase growth of new spears.  After the cutting season allow foliage to form, so the crown can be fed and grow.  

Year 5 - 20: look after your plants (see below) and you can cut spears for a full 6 - 10 weeks every year for many years to come.  Asparagus reaches its prime after 6 - 8 years.

It has been reported that in optimum warm conditions spear growth rates can approach 1 cm per hour.  That may not happen in Tasmania, but it is still prudent to watch spears as they progress.  It is not worth cutting a spear once its tip has opened.

Let's keep an eye on this one.  It will soon be ready for cutting!

How to cut spears?

Maintenance

• Throughout the year keep your Asparagus patch weed-free and support foliage with stakes.
• For best performance keep soil moist, but not sodden, at all times.
• Asparagus plants go into a dormancy period over winter.  At the start of this foliage goes yellow and can be cut off at ground level.
• In mid winter add compost, a complete organic fertilizer and mulch to give the crown plenty of food to produce new spears in Spring.
• Asparagus is not very prone to pests and diseases.

Be patient with your Asparagus plants and you will have a very nutritious delicious crop each year.  Asparagus is high in potassium, calcium, iron and Vitamin C. There is nothing nicer than growing your own and having it fresh from the garden.