Asparagus is a perennial vegetable with three primary parts: the fluffy top is called the fern; the crown is the part just beneath the soil and the roots extend down from the crown. Each spring new edible spears (stems) emerge from the crown. To promote growth this season, last year’s stems and ferns needs to be removed now.
Old spears and ferns can be removed by hand or by gently tilling or mowing, using caution not to damage the crowns. Burning is another option if it is safe and legal to do so.
Asparagus spears emerge from early to mid-April in Manhattan but earlier in southern Kansas and later in northern Kansas.
Fertilize asparagus after the harvest, as needed, based upon a soil test. General recommendations are to apply 1 to 2 pounds of 10-20-10 or 11-15-11 fertilizer per 20 feet of row. If only nitrogen is needed, apply 1 pound of 16-0-0 or ½ pound of 30-4-5, 27-3-3 or similar fertilizer per 20 feet of row. Most of these high nitrogen fertilizers are lawn fertilizers but can be used for this crop as long as they don’t contain a weed preventer or killer. Water in the fertilizer application with ¼ inch of water. (Cynthia Domenghini)
Controlling Weeds in Home Garden Asparagus Beds
The best time to control weeds in asparagus is early spring before the asparagus emerges. A light tilling (or hoeing) that is shallow enough to avoid the crowns will eliminate existing weeds. Many gardeners like to mix in organic matter during the same operation.
Herbicides can be used before asparagus emerges as well. Glyphosate (Roundup, Killzall) will kill weeds that are actively growing, and the preemergence herbicide trifluralin can be used to kill weed seeds as they germinate. Trifluralin is found in several products, but not all of them list asparagus on the label. Those that do have asparagus on the label include Miracle-Gro Weed Preventer Granules and Monterey Vegetable and Ornamental Weeder. Mulch can also be used to keep weeds from invading.
No herbicides can be used during harvest. The end of harvest presents another opportunity. Remove all fern and spears and apply glyphosate (Roundup) to control virtually all of the weeds present. After the harvest season is past and the asparagus starts to regrow, options are limited. Products that contain sethoxydim can be applied to asparagus to kill annual grassy weeds such as crabgrass. Sethoxydim has no effect on broadleaves including asparagus. Two sethoxydim products available to homeowners and labeled for asparagus are Monterey Grass Getter and Hi-Yield Grass Killer. With broadleaves, the only option is to pull them and look forward to next year.
Ward Upham, Extension Agent