As one of the longest lived perennial vegetables, asparagus needs careful attention when planted. The tasty spears and 3-8 ft. high ferny growth will be a significant part of the food garden for 15 years or longer. A dedicated bed in full sun will produce a bountiful supply, enlarging slightly each year.
Soil Preparation and Planting
- Purchase 2-year old crowns (roots, rhizomes, on a budded base) in late winter to early spring.
- Add ample aged manure or compost to beds to improve aeration and drainage, digging in amendments at least 1 ft. deep. Or apply a combination of wood ashes, bone or blood meal, and plenty of leaf mold.
- Dig a long trench into amended soil 12-18 in. wide and 12 in. deep for each row to be planted, reserving removed soil. Loosen another 6-12 in. of soil in bottom of trench. Allow 3 ft. or more between rows.
- Place 2 in. of improved, reserved soil in trench; set crowns 12 in. apart at the bottom of each trench, spreading roots out as far as possible.
- Cover crowns with 2-3 in. of reserved soil; irrigate in the absence of rain.
- Continue to fill each trench with reserved soil as shoots emerge in the first growing season.
- Spread compost or organic mulch 2-4 in. deep between rows once spears have reached the surface to provide nutrients, preserve moisture, and control weeds.
- Avoid excess watering by checking soil moisture 4-6 in. deep before irrigating.
- Supplement with a balanced fertilizer each spring, following package directions.
- Remove dead foliage in late winter and spread 2-4 in. of composted material over bed.
- Allow plants to develop strong roots by refraining from harvest until the 2nd, or preferably, 3rd year if crowns were only 1-yr. old at planting time. Allow an extra year for a seed-planted crop.
- Select only a few 6-8 in. spears for the 1st harvest over a 2-3 week period, leaving the rest to develop into foliage.
- Increase harvest each year, taking care to cut just at the soil surface, continuing for 4-8 weeks every day or every other day while buds at the top of spears are tight and smooth.
- Discontinue harvesting when new spears are less than ½ in. in diameter. Allow all remaining spears to elongate and develop ferny foliage that will restore food and energy to the roots.
- Alternatively, after the 4th year, harvest only half the crop in early spring. In July or August, cut the remaining half, which now has tall ferny foliage, to the ground. Then harvest new spears that emerge.
- Stake tall foliage in high-wind areas. Do not remove ferny, green growth needed to nourish roots and the expanding rhizomes for the next harvest.
- Sonoma County Master Gardener Vegetable Planting Summary.