Asparagus

Asparagus is one of the foods you either like or dislike.  If you like asparagus you might wonder if you could grow it in your garden.  The answer is probably, it depends on your climate, your patience level and whether you have room in the garden for a permanent resident.  Asparagus is native to Europe, North Africa and west Asia.  It has naturalized, or gone wild, in many places in America.

The plant has been cultivated and/or gathered in some places since at least 7000 B.C.  It didn’t become a common edible or garden plant in Europe though, until the 1500’s. Currently the world’s largest producer of asparagus is China.  In the US California, Michigan and Washington State produce the most asparagus.  Mexico produces and exports a lot of asparagus too, another crop you may miss in a trade war.

Asparagus is a perennial plant and you‘ll have it in the garden for a long time.  You’ll need patience because you won’t get a crop the first year you plant asparagus and only a small crop the second year.  You will also need some patience and dedication for removing weeds year after year.  Climate is important too.  Asparagus does well in planting zones 3-7.  They may grow in warmer zones but when they do not get enough cold to make them go into a dormant state they are easily killed in a winter cold snap.  They also don’t make a strong spring crop if they haven’t been in winter dormancy.

Mature asparagus plants are feathery or ferny looking, medium green plants.  There are separate male and female plants. They produce small white flowers in summer and red berries in fall if they are female plants.  Berry production takes energy so female plants don’t produce as many spears in the spring.  Male plants can be produced by division and many nurseries will sell only male crowns (divisions or small plants).

Varieties of Asparagus

‘Jersey Supreme’ and its male only cousin ‘Jersey Knight’ are commonly offered varieties.  ‘Millennium’ is a new, productive mostly male variety. ‘Martha Washington’ is an old and favorite variety.

‘Purple Passion’ and ‘Pacific Purple’ have purple spears that turn green when cooked. Purple varieties of asparagus are said to be sweeter than regular asparagus.

Planting asparagus

Choose the site for your asparagus bed carefully.  It will need to be undisturbed for many years. Asparagus beds will produce well for 15-20 years.  Asparagus does well in well drained, loose fertile soil with a pH of about 7 (neutral).  In the north beds should be in full sun, in the south partial shade or light shade will work.  Remember you will have a harvest period of about 6 weeks in a mature bed but the rest of the year the crop will become a bushy mass of ferny looking leaves about 3-4 feet high.

I highly recommend you prepare a bed for asparagus the fall before you intend to plant the crop.  Add organic matter and composted manure to the bed site and till it in.  Try to get as much grass and weeds out of the site as possible.  How big of a bed you prepare depends on how well you like asparagus.  A bed 2 feet by 20 feet will probably be fine for a family of 2-3 once the bed is mature, if you are moderate asparagus eaters.  The bed will slowly enlarge if you allow it to, so you may have more plants a few years down the road.

You can start asparagus from seeds but I highly recommend you start your patch from “crowns”, which are small dormant plants.  You’ll gain a year on the harvest and you can purchase male plants, which are more productive than females.  Crowns look like a bud on top of some long brown roots.  They are usually sold in packages of 25. That’s enough to start that 20 foot bed mentioned above. 

Here’s how to plant the crowns.  Plant them right around the time of your last frost in the spring.  In a well prepared bed of loose soil make a furrow down the center of it about 8 inches deep.  In the center of the furrow form a mound about 4 inches high.  Think of a ‘w’ where the center point is lower than the sides.

Set the plant on the center mound, bud up, and splay the roots to both sides of the mound. Space plants about a foot apart.  Then gently fill in the whole trench.  The top of the bud portion should only be 2-3 inches below the soil level.  Water the bed to settle the soil.

To start asparagus from seed sow the seeds in individual cells about 14 weeks before your expected last frost. They need warmth, about 75-80 degrees to germinate well.  Grow seedlings in strong light, a few inches beneath grow lights.  Transplant the seedlings to the garden after the last frost, planting them in a trench similar to that of the crowns as described above.

Keep the new asparagus patch well-watered the first year to get it established.  Do not cut the fronds down – let them die naturally in winter. (You can remove them when they are completely brown after a hard frost.) Each year as the ground thaws in the spring apply a slow release general purpose, vegetable garden fertilizer around the plants as the label directs.  Adding compost to the bed in fall is also a good idea.

Many people are growing asparagus in high tunnels and hoops now to produce earlier crops.  Early asparagus could be a money maker in farmers markets.

Problems of asparagus

The biggest problem people have with an asparagus bed, (and you can ask any horticulturist who deals with the public what question he or she most often gets about asparagus), is keeping weeds out of the bed.  You must start early and be vigilant with weeds the entire year.  Use some good mulch such as shredded leaves, chopped straw, or shredded bark around the plants to help smother weeds. 

Once an asparagus patch gets overgrown with grass and weeds it’s almost impossible to get it clean again.  Asparagus competing with grass and weeds won’t give you as big a harvest and is more prone to disease and insects.  It also looks like a mess. Therefore keep the weeds out! 

You will undoubtedly be told at one point or another that you can use salt around the asparagus and it will kill the weeds without affecting the asparagus plants.  That’s not true.  Asparagus is somewhat salt resistant.  The first year you try adding salt to the bed it may seem like it works to some degree, but weeds will be back the next year, maybe more tolerant to salt themselves.  You will probably treat with salt again and then you will start having problems.  Salt only moves through soil out of the range of plant roots slowly, especially in clay soils.  Eventually it starts affecting the growth of the asparagus plants and it’s ruining the soil for many other plants should you decide to rip out the asparagus patch.  Don’t use salt to kill weeds in asparagus patches.

There are no really safe herbicides, (chemicals), that will remove weeds and grass from an asparagus patch.  Hand weeding and mulch are your answers.   If the patch gets really overgrown you should consider starting over in a new area.  You can dig your current patch up in the fall after it goes dormant, separate crowns from weed roots and plant over in a clean spot.  Or you can buy new crowns and kill the old patch by constant mowing or using a herbicide.

Other problems that asparagus patches may have are asparagus beetles and rust.  Asparagus beetles eat the fronds and weaken the plants.  Since they appear after harvest you can spray with a pesticide.  Or you can hand pick the little buggers, or just hope the plants survive.  Rust is a fungal disease. It doesn’t generally kill but weakens plants.  There are rust resistant varieties you can buy. You can use a preventative fungicide on plants if you generally have problems with rust.  Thin out the patch to increase airflow, good airflow helps prevent fungal disease.

Harvesting asparagus

You eat the stems of asparagus in early spring as they emerge before they unfold their leaves.  If you cut and eat all of the “spears”, as the stems are called, the plants will be greatly weakened or may die.  They need the leaves to provide food for the root system.  New plants generally have only one spear emerge and if you cut that it is very energy intensive for them to replace that.  They may not be able to recover.

So here’s part of that patience you need to grow asparagus.  The first spring when you plant crowns or seedlings you should not cut and eat the spears.  In the second year after planting crowns you may cut about a third of the spears that appear one time.  Do not cut the spears of seedling planted asparagus the second year.  In the third year you can take more spears from the crown planted crop, about half, and for 2-3 weeks and in the seedling planted crop about a third of the crowns one time.  In the fourth and following years you can get a normal harvest for crown planted beds and a half harvest for seedling beds that year, full harvest after the next year.

A normal mature bed harvest means cutting spears for about 6 weeks in the spring, and you can cut most of the spears you need.  To harvest asparagus let the spears get 6-8 inches long and about the size of a pencil, then snap or cut off the spears at ground level or slightly below. After 6 weeks you should stop cutting and let the spears mature into leaves. 

Asparagus spears have the best flavor if cooked right after harvest.  If you need to store them place a little water in a pan, bowl or jar and stand the spears upright, tip up, in it.  You may have to tie them in a bundle.  Refrigerate. Asparagus can be canned, pickled, or frozen to preserve the harvest.

Asparagus is considered to be a healthy food, low in calories, rich in vitamins and minerals and fiber.  It is a diuretic however and when that urine leaves the body it has a very distinctive strong odor. This can happen 15 minutes after consuming the plant.  Interestingly while most people produce the smell after eating asparagus, some people can’t distinguish the odor.  In 2010 this was found to be caused by a genetic variation in olfactory genes.