Asparagus is a perennial vegetable that is started in the home garden by setting out seedling transplants, or more commonly by planting “crowns” in winter. Crowns are actually roots collected from one year old plants and are available for purchase at local nurseries. Gardens established with crown plantings are ready to harvest edible spears one year earlier than if the asparagus garden was started with seeds. Even with crowns, however, it will take a few years to develop a strong bed of asparagus plants that can support a weekly harvest for eight to 10 weeks in early spring. The good news is that once established, an asparagus garden can last more than 10 years.
Plant asparagus in areas that receive full sun. In order to grow an asparagus bed that requires minimal care over the years, it is important to select a weed-free area in the yard. Stay away from areas with nutsedge, bermudagrass and other perennial weed problems like johnsongrass or field bindweed. Take the time to properly prepare the soil. Start by working the soil a foot deep, mixing in large amounts of compost, steer manure, peat moss or a similar organic material. At this time, also mix in some 12-12-12 or 16-16-16 fertilizer. Or, if you prefer, you may use an organic fertilizer.
Asparagus roots spread widely, so plant them in rows about 4 feet apart. Dig a trench 9-10 inches deep and place large crowns about one foot apart. Make sure that the crowns do not directly touch fertilizer. Cover the crowns with two inches of soil, water, and then let the crowns settle and grow. As new shoots emerge, gradually fill in the trench with additional soil. Eventually, you will develop a slightly raised bed of soil-covered asparagus plants.
We advise you plant varieties that have disease resistance, especially to fungus like fusarium wilt. Plant about 10 crowns per person.
Asparagus should be well-irrigated throughout the first year. In following years, asparagus should be watered mostly during the fern season in the summer, not the harvest season in the spring. Remember not to harvest the first year and only harvest for a few weeks in the second year. By year three, the bed of asparagus plants should sustain a 10-week harvest schedule.
Edible asparagus spears are young shoots that are cut about 8 inches long at the ground surface. If left to grow, they develop into fernlike leaves. The plant continues to push new shoots until the weather turns hot.
Spears can grow at a rate of 3 to 6 inches a day, depending on the spring weather. When spears reach approximately 9 to 10 inches tall, they are hand-cut at ground level with a knife. Harvest spears every two to three days and immediately store them unwashed in the refrigerator within a vegetable crisper. To prevent the spears from drying out too rapidly, place the butt ends on a wet pad. If rapidly cooled and held at 36 degrees, asparagus may be kept for two to three weeks. Commercially, spear sizes range from colossal (one inch diameter), down to small (about one quarter inch diameter). The standard size is five sixteenths (5/16) of an inch diameter. Spear toughness is more related to postharvest handling and not spear size.
Water and fertilize the plants during the summer fern season, so plants can manufacture food to be stored by crown roots for next year’s shoot growth. To apply fertilizer in a band, dig a furrow several inches deep along the side of the planting row, sprinkle the fertilizer evenly along the furrow, cover it with soil and then water it in.
Ferns will turn brown in the fall, indicating that carbohydrates (future food reserves and energy) have been transferred to the roots. At this time, cut ferns back and allow plants to enter winter dormancy. In spring, new shoots will appear, starting the cycle again.
Armyworms, aphids, thrips, and garden symphylans are occasional pests in asparagus, but rarely a big problem. Pest management information is available from the UC IPM web site under home gardens and landscapes, ipm.ucanr.edu/home-and-landscape/asparagus/index.html.
Whether you grow your own asparagus or not, be sure to eat your veggies!
The Master Gardeners will be live to answer your questions on Saturday, March 5, 8 to 11 a.m. at the Visalia Farmers’ Market in the southwest parking lot of Sequoia Mall in Visalia; and at Ace Hardware in Visalia from 10 a.m. to 1 p.m. You can also contact them at 559-684-3325, or visit their web site at ucanr.edu/sites/UC_Master_Gardeners.
