Britney would love these spears

Asparagus is one of a very few vegetables that needs to be planted only once. Believe it or not, this plant will produce delectable spring shoots for 100 years if left perfectly alone.

Virtually unique as a perennial vegetable, harvests of the tasty spears return year after year. And in my opinion, the only guaranteed way to really get the tastiest, young and tender spears is to raise your own.

The edible part is the young shoot, harvested before it matures into a leafy, fern-like stem. It does best in full sun. Because it shades out other plants and doesn’t need seasonal replanting, it should be grown apart from the rest of the veggie garden. This is why the specific part of the garden set aside for this plant is called the asparagus patch.

A well-established and productive asparagus bed needs to be thinned as it matures. In fact it can often be found growing in the wild where a gardener or farmer might have planted it generations ago. But dividing and transplanting will increase the number of asparagus plants, and thus the yield. So go ahead and expand your patch or gift some of it to friends and neighbors.

Now is the time to start or expand your asparagus plot. Move it to a sunnier spot or beg some roots from your neighbor. The next few weeks are the time to buy year-old crowns and get them planted. And yes, asparagus is related to our houseplant, the asparagus fern—which is not a fern at all, but a true asparagus that also thrives in full sun, not the shade of your darkest corner.

Asparagus crowns are sold in garden centers, online and by mail order. Crowns are spider-like clusters of roots measuring perhaps 8 inches in diameter. These are purchased as bare root plants, not in pots or soil, but simply bundled with exposed roots in units of one or two dozen. Each crown, distinguished by a cluster of pale green or white knobs that later become shoots, can go into a separate planting hole. As the plant grows, it spawns new crowns. Eventually, it becomes a whole mass of root clusters, overlapping each other under the soil surface.

Above the soil, the plant gets larger and fuller over the years and the harvest of green shoots in May or June gradually grows from a half-dozen spears per plant to more than two dozen. Approximately two dozen crowns will be enough to feed two people, so plan accordingly. Also keep in mind that you should consider buying all male plants, as they are more productive than their female counterparts, which expend part of their energy reserves on producing flowers.

Avoid the temptation to cut the stalks the first year, as letting them grow and mature the first season without being disturbed is critical in establishing a vigorous patch. Getting to the stage of two dozen spears per plant will generally take between three and eight years, depending on the variety of asparagus, the quality of the soil and other environmental conditions. But, always, your first harvest should be stalled until the second season after planting. The best crowns will come from plants that have been in the ground at least three years.

To begin the dividing process, first cut back the fern-like foliage to about 6 inches. This will make the plants easier to handle. Don’t worry, the foliage is dying back anyway this time of the year. Next, with a garden fork or sharp spade, define a crisp vertical trench around the plant, leaving a soil area of about 4 inches between plant and trench border. Then, dig the plant gently with the fork. Some roots will get nicked off in the process, but this will not harm the plant. Once the entire asparagus plant is loose, lift it out of the ground and gently dislodge as much soil from the roots as possible.

The real work begins as you untangle the interlocking crowns and roots. Work carefully to minimize trauma to roots. Divisions can contain perhaps three to four crowns, which saves you the trouble of separating each crown, but the trade-off will be in fewer new plants. Whether you settle for crown clusters or individual crowns, discard the smallest crowns or combine them with larger ones in the new location.

The planting techniques are the same for expanding old plots or establishing new ones. The new soil should be loamy, well drained, high in organic material and deeply dug. I’ve never met a new asparagus bed that didn’t thrive when the original planting was done with tons of well-rotted (aged) manure.

The soil should be cultivated all around the new plant to a depth of at least 8 inches. The plants can go in individual holes, or better yet, dig a long trench. But make sure that each planting has at least 12 inches of space to itself.

Cover new plantings with soil and compost and tamp down firmly before you water. Water gently. The initial watering can contain a biostimulant, but no fertilizer. Or you can schedule the project just before rain is expected, then add the biostimulant and cover the whole thing—cropped foliage and all—with a thick mulch of shredded leaves or more well-rotted manure.

Asparagus beetles are the only potential problem. But if they are controlled early with neem oil or insecticidal soap, they can be quickly eliminated. If allowed to hang around, though, they can be a perennial problem year after year.

Fall care for established asparagus includes intense weeding to remove persistent perennial weeds from the bed. This is topped by a dressing of compost, well-rotted horse manure (disinfectant free if you are going to get some locally), leaf mold or ready-made compost—all of which are excellent. Topping should be about 4 inches thick, covering the whole bed. Mulch through the winter with leaves, preferably shredded, and you’ll have excellent spears next spring.

Cutting back foliage from mature asparagus is largely a matter of preference. If you are trimming back, leave a few inches of growth above the mulch line so that you will know where the plants are next spring.

Need more information? Curious about white and purple asparagus? Point your browser to the website asparagus.org and click the link on the left titled “Asparagus in the home garden.” And of course, keep growing.

Andrew Messinger has been a professional horticulturist for more than 30 years. He divides his time between homes and gardens in Southampton, Westchester and the Catskills. E-mail him at: Andrew@hamptongardener.com. The Hampton Gardener is a registered trademark.