After a long winter with no fresh homegrown vegetables many gardeners really look forward to that first spring harvest of asparagus and rhubarb, said David Graper SDSU Extension Horticulturist and Director of McCrory Gardens.
“These popular vegetables are actually perennials that come back year after year to provide a bounty of delicious and nutritious food for main meals and desserts,” Graper said. “Many asparagus fanciers take to scouring the road ditches and fence lines for these delectable spring shoots while others chose to establish a patch in their own gardens.”
Graper said 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 said 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.
Then, 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 that is usually more productive.
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.
Small, new shoots will soon begin to grow. As the new shoots develop, Graper said 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.
By the third year, he said 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.
Rhubarb is also best planted in the spring in a clean, weed free area. It needs full sun and a well-drained soil. Most people will plant using crown divisions that they purchase from a nursery but, Graper said gardeners can also get a division from a friend.
Work the soil well before planting. Incorporating some compost or well-rotted manure can also help get your plants off to a good start. Dig a large enough hole to easily accommodate the transplant covering the buds with a couple inches of soil. Rhubarb can also be planted from seed in the spring but there are more varieties with the nice red colored petioles or stalks available as transplants than from seed. Also, Graper adds that seed-grown plants tend to produce more seed stalks than the vegetatively-produced plants.
Once again, it is best to not harvest anything from your rhubarb for the first two years. In year three, you can harvest a few of the stalks but leave the rest to mature and continue to build up the plants.
When harvesting, Graper encourages gardeners to grasp the leaf stalks close to the ground and give a firm tug to harvest them from the plant. Cut off the large leaf blade and add those to the compost pile that will leave the edible petiole. If seed stalks develop, cut them off close to the base of the plant. Allowing them to develop will take some energy from the plant so it is best to remove them.
Weeds are the biggest problem with growing these perennial crops. Graper said 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.
Both asparagus and rhubarb 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.