Growing Asparagus in the Perennial Garden

Text by Brian Barth

Asparagus undergoes a dramatic metamorphosis through the course of each growing season. As soon as the ground warms in spring, green stalks pierce the crust of the soil like slender paintbrushes. This, of course, is the portion that we eat. Let the asparagus spears continue to grow, however, and the tight, pointy bundle of buds at the top of each begins to unfurl into a plant that is at once Jurassic and Zen. Asparagus is a foliage plant beyond compare, the primordial vigor of its growth habit balanced with the ethereal grace of its form.

The lacy, seemingly leafless fronds of a mature asparagus stalk in summer are worthy of any perennial border. Come fall, the red berries of female asparagus plants complete the show. Even the darkened stalks that have been browned by a hard frost add interest to the late fall and early winter garden. As one of the few perennial vegetables—it’s hardy from Saskatchewan to South Carolina—asparagus makes an important element in the edible landscape repertoire.

Design Ideas
Growing three to five feet tall, asparagus fits in the mid-ground of perennial border compositions. Use smaller brassicas, chard and other ornamental greens in the foreground. Or, combine it with low-growing ornamentals that complement its loose, airy texture, such as Carex comans ‘Bronze Curls’ and Geum x‘Marmalade’. Plant sunflowers, cardoon, indeterminate tomato vines, tree dahlias or shrubbery of a contrasting leaf color behind it.

Asparagus beds remain productive for 15 years or more, so you can consider it a long-term anchor in a cottage garden or formal border design. The plants also fit right into modernist themes—framing them in a bed of weathering steel (often referred to as Cor-Ten) or with backdrop of horizontal latticework is a nice touch.

Let the bed shape be dictated by the overall design surrounding an asparagus patch. If rectilinear raised beds of flowers and vegetables structure your garden, strategically insert a few narrow beds dedicated to asparagus throughout the design. (A single row of asparagus requires a bed width of only 18 inches.) This breaks up the annual plantings with a perennial that behaves well in all four seasons. Or, if your border is built along a meandering berm, asparagus serves as a fitting specimen for a swath of foliage following the peak of the berm. It will appreciate the deep soil and give definition and unity to the planting. Asparagus has such a soft form that massing it will never have the effect of visually dominating a planting.

Growing Asparagus
Asparagus requires full sun, or filtered light in hot climates; neutral soil pH; regular moisture; and rich, well-drained soil. It is hardy in USDA Zones 3 through 9.
In late winter or early spring, plant bare-root crowns in trenches 8 to 10 inches deep and cover them with an inch of soil; add soil as the spears grow until the trench is filled.

Asparagus has such a short window of harvest, it pays to plant more than you can eat and then pickle the remaining spears as an easy appetizer to enjoy during the rest of the year. Allow the planting to become established for two years before harvesting, and then pick all spears that are at least the diameter of a pencil in spring. You have to be vigilant to get the spears in their prime tender state, however. They grow up to six inches per day in spring; if they’re not harvested daily, you’ll miss the brief time where each spear is tall enough to pick, but not so tall that is becomes tough and chewy. Of course, you can’t pick every spear that pokes through the crust of the soil, or the plant will not photosynthesize enough to store energy for next year’s harvest. After four weeks of harvesting, let the majority of the stems spread their delicate wings and soak up the sun’s rays for the rest of the year.

Brian Barth is a landscape architect who specializes in urban farms and edible landscapes.

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