Tender, tasty asparagus spears are a spring-time treat, but you’ve got to start early if you want to serve these nutritious vegetables—a year or two in advance, in fact. That’s because you’ll get better results if you harvest conservatively for the first few years after the crowns are planted. Eventually, with the proper care, you’ll have an asparagus bed that may produce for 15 years or more.
Start by preparing a bed for your plants in autumn. In warm climates, asparagus can be planted in the fall; in cooler regions, plant in early spring, about a month before the last expected frost.
Purchase one-year crowns, which are the root systems of the plants. (You can plant asparagus from seeds, too, but sowing the seeds and transplanting the seedlings takes extra time and effort.)
Make the bed by digging a trench and clearing it of all weeds and grass. Asparagus grows best in slightly acidic soil that drains easily, in USDA hardiness zones 4 to 9. Give the plants part sun.
'Jersey Knight' is a hardy, vigorous asparagus that produces large but tender spears. It is disease resistant and performs well in many soil types.
Gardeners were once told to dig trenches up to 18” deep to plant asparagus, but new varieties like ‘Jersey Supreme’, ‘Purple Passion’, ‘Jersey Giant’ and ‘Jersey Knight’ can be planted in trenches dug from 6” to 12” deep and about 12” wide.
Because these new varieties are all-male cultivars, they don’t expend a lot of energy producing seeds, and produce high yields and earlier harvests. They also show good resistance to fusarium rot and asparagus rust, two problems growers often encounter.
Before planting your asparagus, work in a 2” to 4” layer of compost and well-rotted manure. Mix the amendments with the native soil to make a mound. Place the crowns on top of the mound, draping the roots over the sides. The crowns should be about 6” below the surface of the soil. Now back fill the trench right up to the crowns, and water in thoroughly.
As the soil settles over time, keep adding more soil until the trench is filled. Eventually, it should be level with the soil around it.
Asparagus can’t compete with weeds or grass, so be vigilant about keeping the bed clear. But be careful not to disturb or damage the shallow roots. Mulch generously with shredded leaves or weed-free straw. Water regularly and consistently.
Now you need patience. Don’t pick the spears from your plants the first year, to give the foliage time to channel energy into the roots. Meanwhile, side-dress the plants in spring and fall with compost.
The second year after planting, harvest lightly, or over a period of about three weeks. The following year, harvest over a 4 to 6 week period. Showing restraint allows time for good roots to form. Keep mulch on the beds.
The spears will be ready to harvest in late spring or early summer, when they are about as big around as your finger. Cut or snap them off before the tips, or the scales at the top, start to open.
Damaged spears in the spring, or damaged leaves in the summer, often signal the presence of asparagus beetles. Hand pick them when possible, or spray with insecticidal soap. Destroy stalks or leaves that have tunnels on them; these are made by asparagus miners.
With a little maintenance, you’ll be picking asparagus for many years to come.