Sweeter and crisper than any you are likely to find in a grocery store, freshly-picked asparagus (Asparagus officinalis) is a taste sensation. If you are looking for any more reasons to plant asparagus crowns in your garden, consider their nutritional value. The spears are rich in vitamin C, calcium, iron and B vitamins. Vigorous in U.S. Department of Agriculture plant hardiness zones 3 to 10, these perennial plants reach 3 to 5 feet in height and are ready to pick in two to three years.
Select a site that receives full sun; you will have stronger plants and cut down on disease. Plant crowns in the late winter or early spring, when the soil temperature is at least 50 degrees Fahrenheit.
Prepare a garden bed that is roughly 4 feet wide and tilled to a depth of 10 to 12 inches. If you have heavy clay soil, consider building raised beds to provide the drainage asparagus plants need. It is hard to overstate the importance of careful soil preparation; these beds will hold your plants for 15 to 20 years.
Dig a trench down the center of the bed that is 12 inches wide and 8 to 10 inches deep. Set the soil aside to use when filling the trench back in later.
Spread a 2-inch layer of compost in the trench. Well-composted plant materials work well, but a mixture of both plant and well-composted animal manure, such as sheep, chicken, horse or cow, is ideal.
Spray the trench with water until it is fully soaked.
Set asparagus crowns in the center of the trench, spacing them 1 to 1 ½ feet apart. Spread the roots out, with the crown's tip facing up.
Tuck a 2-inch layer of soil around the crowns, using the soil set aside after digging the trench. Thoroughly soak the area and let the crowns rest until the new shoots peek out.
Add additional soil around the shoots as they grow, always leaving the tips uncovered. Expect to add soil roughly every two weeks, and continue until the trench is filled in.
Water regularly and mulch to maintain a more even soil moisture and to control weeds. In a Mediterranean climate, stop watering in the fall, to allow the plants a necessary dormant period.
Prune the ferny stems to the ground when they turn brown at the end of the growing season. Remove all the debris to discourage any insects from overwintering in it.
Harvesting and Tending
Harvest asparagus plants in their second year of growth, and then only cut the spears that are larger than pencil thickness. The plants need time to build up a solid root mass. In a few years, harvest usually takes off.
Cut spears when they are thicker than a pencil and 5 to 8 inches tall. Use a sharp knife to slice spears at or below ground level.
Tuck new compost around the plants every spring and fall, to maintain vigorous growth.
Things You Will Need
- Garden hose
- Asparagus crowns are dormant rootstock. Buy all-male crowns like “Jersey Giant” and “Jersey Knight” for higher yields. Because they are not diverting any energy to making seeds, male spears tend to be larger and more numerous than traditional cultivars with both male and female spears. Heirloom cultivars such as “Purple Passion” will have lower yields but produce a wider variety of colors and flavors.
- In the second year of harvest, only cut spears for four to six weeks. In the third year and beyond, harvest goes on for up to 10 weeks. When the spears are less than a pencil’s diameter, it is time to stop cutting.
- Allow 10 to 20 crowns per person when planting heirloom varieties, and six to seven plants per person when planting all-male cultivars.
- If you cannot get the crowns in the ground right after you bring them home, wrap them in damp sphagnum moss until planting time.
- Rodale’s Ultimate Encyclopedia of Organic Gardening; Fern Marshall Bradley, Barbara W. Ellis and Ellen Phillips, editors
- Floridata: Asparagus officinalis
- Missouri Botanical Garden: Asparagus Officinalis
- Sunset Western Garden Book; Kathleen Norris Brenzel, editor
- Marin Master Gardeners: Growing Asparagus in Your Garden
- Grow Organic: Asparagus
- Stockbyte/Stockbyte/Getty Images