Hardiness: Zones 3 and warmer
Climate Zones Maps
Light: Prefers full sun, tolerates some shade
Soil: Fertile, well-drained; prefers pH 6.5 to 6.8; will tolerate slightly alkaline soils, up to 7.5
Water: Regular water, keep soil evenly moist, but not wet
Spacing: Plant crowns 1.5 to 2 feet (.45 to .61 m) apart in rows 3 to 4 feet (1 to 1.2 m) apart
Harvest: Begin harvesting after two to three seasons of growth
Asparagus tends to grow best in areas where soil freezes in the winter. Avoid low-lying areas that get heavy dew or morning fogs to reduce the possibility of rust.
Planting & Growing Guidelines
Can be grown from seed or one year-old crowns. One year-old crowns are less prone to transplant shock, but two year-old crowns have more roots, either are good.
Buy crowns with roots that are fresh and firm and healthy looking. Plant crowns immediately after you get them home, or keep them in slightly moistened sphagnum moss.
Dig a trench 8 inches (20 cm) deep in well-composted soil. Build a 2 inch (5 cm) mound of soil or compost down the center of each trench. Set the crowns in the trench 1.5 to 2 feet (.45 to .61 m) apart with their roots draped over the mound, fanning the roots in all directions.
Cover the crowns with soil to half the depth of the trench. When foliage starts to show above ground level, finish filling the trench with soil. Mulch or cultivate shallowly to keep weeds under control, and keep moist but not wet.
After you are finished harvesting, it is critical to allow the foliage to grow lush and healthy to ensure next year’s crop. Each fall, cut back the dead foliage, rake it all off, and mulch heavily with compost. Early each spring, carefully rake off all but 1 to 2 inches (2.5 to 5 cm) of the mulch to let the spears emerge.
- Helpful Articles: The Wonders of Mulch – A Complete How To Use Mulch Guide
Fertilizing Asparagus works hard and needs to be fed twice a year. In the early spring, while the crowns are still dormant, or the budding shoots are still a good two inches (5 cm) under the soil, sprinkle a good balanced fertilizer like a 5-5-5 or a 10-10-10 around the crowns.
Use 1 quart (1 l) for every five feet (1.5 m), and sprinkle the fertilizer about 6 inches (15 cm) from the crowns and in all directions. As soon as harvesting of the spears is done, weed the patch carefully, and side-dress with a 10-10-10 fertilizer at the rate of 1 quart (1 l) for every 5 feet (1.5 m).
Asparagus plants need to start storing energy back into their crowns and roots after harvest, so allow the spears to grow up and turn into leafy ferns, because that is where the food for the plant is manufactured.
Pest and Disease Prevention for Asparagus
Asparagus rust can be a serious problem in damp locations; use rust-resistant cultivars. Reduce damage from asparagus beetles by getting rid of the old asparagus foliage in the fall. Asparagus beetles like to overwinter in garden debris and emerge in the spring to feed on young asparagus spears. Keep area clean of debris and cultivate the asparagus patch shallowly before applying mulch in the fall.
Common Problems: Perennial weeds and grasses can be a problem in an asparagus patch. Make sure the area is free of weeds before planting and mulch or cultivate to keep them out.
Days to Maturity: Asparagus may be picked sparingly for 1 to 2 weeks in the second year. A mature patch, around 5 years old, may be harvested for as long as 10 weeks. The average is 1 pound (500 g) or more of asparagus for each linear foot (30 cm).
Harvest and Storage
Begin harvesting after two to three seasons of growth. Carefully cut the spears at ground level. Some people like to snap them off, but this leaves a woody stem behind that can invite insects and disease.
Harvest while the tips of the spears are still tightly closed and pick nothing smaller than the thickness of your small finger. In warm spring spells, this may require harvesting daily. Can or freeze extra spears.
Note about White Asparagus
To grow white asparagus the plants must be at least 3 years old. In the early spring, when the asparagus spears start to come out of the soil, cover them with anything that will block the sunlight from the asparagus spears.
The key behind making white asparagus is to block the sunlight. The easiest way is to put a plastic tub over the spears, mounding soil can also be done, but it is labor intensive. In the evening slightly lift up the tub so there is an air flow around the asparagus spears. It is important to have an air flow but still block the moonlight.
The tub can be wedged up by putting a piece of wood under the tub. Remove the wedge of wood every morning to continue blocking any sunlight. When the asparagus spears reach 7 to 9 inches (18 to 23 cm) tall they can be harvested. The best way to keep asparagus spears fresh is to prepare a container that can hold ice water, and as the spears are picked, place them in the container of ice water.
Special Tips: In heavy soils, plant in raised beds to improve drainage. Lay crowns at ground level rather than in trenches and mound soil over them.