Asparagus (Asparagus officinalis) is a member of the lily family and related to onions, leeks, and garlic. Prized by the Greeks and Romans, this perennial is believed to have originated in the temperate regions of southwestern Asia and the Mediterranean basin.
Widely cultivated in the United States, top production states include California, Washington, and Michigan, though New Jersey grows commercially and Rutgers University researchers are credited with developing many of today’s most popular varieties. Due to demand and falling acreage, imports from Mexico, Peru, and Chile augment supply.
Asparagus plants are particularly resilient and have been known to grow wild (often called ‘sparrowgrass’) along railroad tracks and roadsides in the United States.
References: Agricultural Marketing Resource Center, Rutgers Cooperative Extension, USDA.
TYPES, VARIETIES & CUTS
There are two main types of asparagus: green or white (blanched). Each refers to the color of the vegetable—white asparagus has a mild, sweet flavor while green has a more ‘woody’ taste that is slightly bitter. White asparagus was popularized in Europe.
Both types have smooth, spear-like stalks with firm, crunchy flesh. The greener or whiter the asparagus, the more tender the spears. Purple asparagus, of mostly French and Italian varieties, is less common. These cultivars are more tender and sweet than their green asparagus siblings.
Varieties of asparagus have shifted in recent years with the older standards such as Mary Washington, Martha Washington, and Waltham Washington losing ground to newer all-male flowering plants (which produce more spears) such as Jersey Giant, Jersey Knight, Jersey Prince, Jersey Supreme, Apollo, Purple Passion, and Viking KBC. Advantages of the newer hybrids include higher yields, better cold tolerance, and resistance to fungal diseases, such as Fusarium rots, and rust.
References: Michigan Asparagus Advisory Board, Ohio State University, Rutgers Cooperative Extension, University of California Cooperative Extension, University of Illinois Extension.
PESTS & DISEASE
Asparagus beetles often overwinter in plant debris and lay eggs on spears in early spring. The resulting grey larvae feed for 2 to 3 weeks before burrowing into the soil to pupate. The larvae will typically feed on spears causing abnormal growth and a crooked appearance. Other beetles, including Japanese beetles can have an impact as well.
Aphids are tiny, bluish-green insects that can seriously affect yields. They feed on ferns causing a distinctive ‘witch’s broom’ appearance. Asparagus is also vulnerable to both white and dark-sided cutworms, grasshoppers, miners, and tarnished plant bugs.
Rust manifests differently based on spore type and season. Oval, green lesions form in spring, then turn orange and sunken. By late summer, new red blister-like lesions appear, and in fall the lesions become blackened. The four different spore types are all spread by wind or rain and often overwinter in plant debris. Planting spacious rows and preventing soil wetness may help reduce the incidence of asparagus rust.
Purple spot is a fungus that causes lesions on the fern and spears, leading to defoliation. It can affect up to 90% of a field, and, when infected plant debris is left in a field, its spores can be spread through wind or rain. The other most common diseases that affect asparagus include crown and root rot from Fusarium fungal infections, phytophthora rot, bacterial soft rot, various types of blight, and spear rot.
References: Cornell University Extension, Michigan State Extension, North Carolina State Extension, University of Illinois Extension.