How to grow asparagus

After a long winter with no fresh home-grown vegetables many gardeners really look forward to that first spring harvest of asparagus, says David Graper, South Dakota State University (SDSU) Extension horticulturist.

He says the best way to start an asparagus bed is to begin preparation in the fall before the spring you want to plant.

First, kill off all of the weeds with repeated cultivation or an application of glyphosate herbicide. He says this can also be done in the spring, but it won't be as easy to get the tough perennial weeds controlled.

"Weeds are the biggest problems for asparagus growers so get them taken care of before you begin," he said.

Order seedlings in early spring

Order fresh 1-year old seedling crowns of the variety you want to plant. It is best to always buy seedling crowns rather than to try to dig up plants from a friend or a ditch, they transplant better and you can select an all-male variety which is usually more productive.

Dig a trench

Plant by first digging a trench about a foot deep and 8- to 10-inches wide. Place the crowns in the center of the trench - about 18-inches apart and cover with about 3-inches of soil.

New shoots will soon begin to grow

As the new shoots develop, Graper says gardeners can gradually fill in the trench, adding another inch or two of soil every few weeks, until you have the trench completely filled up. Allow the new shoots to grow all season without harvesting for the first two years.

Only cut them back to the ground after they have been killed by a hard freeze in the fall. It's a good idea to cover the row with a good 3- to 4-inch layer of organic mulch each fall. Shredded leaves and grass clippings work well.

"The mulch will also help reduce weed growth in the patch," Graper said.

Don't pick for three years

By the third year, he says the asparagus should be getting pretty well established and should be healthy enough to take a couple harvests of the shoots, but then let them grow up and remain until the end of the season again.

In the fourth year, gardeners should be able to harvest for about six weeks. But, stop harvesting if you notice that the size of the shoots is getting smaller, down to the size of a pencil.

Weed control

Weeds are the biggest problem with growing perennial crops. Graper says gardeners can hoe or till right over an established asparagus patch in the spring before the new shoots start to grow. Or, one can carefully apply glyphosate herbicide to perennial weeds before new shoots emerge in the spring too.

"But do not get the spray on any asparagus shoots as this can severely damage the plants," he said.

A good layer of mulch and keeping a clean border around the plants is the best way to avoid weed problems. Do not use salt to kill weeds. While this may kill the weeds it is also damaging to the asparagus.

Fertilize every year

Asparagus will benefit from a yearly application of fertilizer after harvest is complete. Gardeners can use a typical garden fertilizer like 10-10-10 applying about a cup per 10-foot of row and scratching this into the soil or you can use compost or well-rotted manure, applying it an inch or two thick over and around the plants. But be aware that you might be introducing weed seeds to your patch which will mean more weeding later.

To learn more, visit iGrow.org/Gardens.