Fresh asparagus is generally the first vegetable harvested in the spring and is welcome addition to any edible garden plan. Asparagus is a reliable and productive perennial vegetable crop for central Kansas gardeners and now is a great time to plan for a new planting. A properly maintained asparagus patch can produce for up to 15 years. Here are a few tips that will help you get the most out of an asparagus planting.
Select the best varieties and order crowns
Asparagus can be propagated from seed but is more often started from 1-year-old crowns. Order crowns in February or early March to ensure they arrive in time to plant.
‘Millennium‘ is a newer and very productive asparagus variety. It was developed at the University of Guelph in Ontario, Canada. It is very cold-hardy and tolerant to harsh winters – but is also has been good performer in warm harvesting seasons. It grows in a wide range of soil types and is long lived. Trials conducted in 2013 in northern Minnesota showed it produced 2,094 pounds per acre compared to 1,287 pounds for ‘Jersey Giant’ and 1,233 for ‘Jersey Knight’. Research in Michigan found plantings of ‘Millennium’ were slower to attain high yields compared to ‘Jersey’ varieties, but they later showed superior and heavy yields over a 15-year lifespan. Overall plantings showed greater vigor and survival. It is being grown in Kansas and shows very good productivity here as well.
Other good varieties to plant include Jersey Giant, Jersey King, Jersey Knight, Jersey Supreme, UC157, Ida Lea, and Purple Passion. These are hybrids that will produce three times as much as older varieties. These varieties live longer, emerge earlier in the spring, are more productive and eliminate potential volunteer plants that can reduce the productivity of a planting.
Choose the asparagus planting site carefully; pick one at the north or west side of your garden so you don’t shade your shorter vegetables and you’ll want to avoid tilling over it.
Proper soil preparation is especially important for perennial crops. Take a soil test to insure proper levels of nutrients. It is easier to adjust soil conditions before planting if that is needed. Work the soil as early in the spring as possible but do not work wet soil as clods will form. Plenty of organic matter is essential since the soil won’t be worked again. Add 2 to 3 inches of organic matter such as compost or peat moss to the surface along with any needed fertilizer and work again so the organic matter and fertilizer are blended into the soil. If no soil test is available you can use any herbicide free starter fertilizer at the rate recommended on the bag.
March 15th to April 15th is the best time to plant asparagus. Asparagus crowns should not be planted until the soil is nearing 50 degrees. It is also best not to hang on to crowns too long and risk them drying out indoors.
Dig a trench 8 to 9 inches deep and place the crowns in it approximately 18 to 20 inches apart. If you plant more than one row, keep the rows 4 feet apart. Traditionally, the crowns are then covered with 2 to 3 inches of soil. When the new asparagus shoots emerge, 2 additional inches of soil are added in the trench being careful to keep some of the new growth exposed. This process is repeated until the soil is filled to the top of the trench by the end of the first growing season. It is important not to compact the soil in the trench. Weed control is also very important during establishment. Competition with weeds results in slow establishment. A shallow hoeing should be all that is needed the first year.
Now comes the hardest part: you can’t harvest this year. Wait patiently until next year and even then, do not pick every spear from the plants. Limit harvest to 3 to 4 weeks during the second year, or until spear size rapidly decreases in diameter. During the third season, regular harvest can begin. Asparagus harvest normally begins in mid-April and the spears can be harvested for 6 to 8 weeks in the spring. If temperatures are warm, asparagus may need to be harvested every three days and if it is hot harvest may be required daily.
Harvest while the tips of the spears are still tight. Spears that become too large should be cut and discarded as this allows new spears to emerge. Cut the spears with a sharp knife or snap them off at the soil surface. Be careful to avoid damaging the new spears getting ready to emerge. A well cared for planting will yield 80 to 100 lbs of fresh asparagus from 1,000 sq ft of bed space!
Care of established plants and common problems
Check out our recently updated asparagus publication for details on care of established plantings and common problems you may see with asparagus in the garden.