Because you are planting asparagus for the long-haul, it makes sense to give a little extra thought choosing the planting location and preparing the bed. You will want to locate the bed in full sun and in a separate plot from your other vegetables as asparagus foliage will shade adjacent vegetables. A new plot that has never been cultivated before is ideal to minimize soil-borne diseases that can attack the plants.
The location should have good drainage, meaning that water should drain off the surface and soak into the soil within a few hours after a good rain. As for soil type, asparagus does best in a fertile, sandy loam or loam soil high in organic matter. This means lots of humus in the soil. Optimum soil pH is 6.5 to 7.0. We do not recommend adding ashes or salt to the soil as a fertilizer or for weed control. All perennial weeds such as quackgrass, Canada thistle, bromegrass and other weeds must be killed, either by cultivation or with an herbicide. If using a chemical herbicide, it must be used prior to setting out the roots.
Upon receiving the asparagus crowns, if you cannot plant immediately sprinkle them with water and cover with slightly damp sphagnum moss or newspaper and keep them in a cool, dark location. Plant as soon as possible. Do not expose the asparagus roots to drying winds or sun.
Before setting the roots, mix well-rotted manure into the top 8 inches of soil. A moderate amount would be 10 to 15 bushels in a row 100 feet long and 2 feet wide. Compost or peat moss can also be used. In addition, the soil should be fortified with plant food by adding a complete fertilizer such as 10-10-10 or a similar analysis. We suggest 10 to 15 lbs. per 100 feet of row. Mix it into the soil thoroughly. Never allow the asparagus roots to come in direct contact with the fertilizer as it can burn them.
Transplanting Asparagus Plants
Set the asparagus roots in a trench or furrow 8 to 10 inches deep with each plant spaced 12 to 15 inches apart. Be sure the buds on each crown are right side up and spread the roots out well. Rows can be 3 to 4 feet apart, or as needed for your preferred cultivation method. Cover the roots and crown with 2 to 3 inches of soil. Water to help settle the soil and give the plants a good start. After the fern-like tops begin to develop, the trench can be filled in gradually. Avoid covering the growing tip. By fall, the trench should be filled in and slightly higher than ground level to encourage good drainage. Keep the bed free of weeds and water the soil to keep it moist. A mulch of hay, straw or leaves can be applied in midsummer to aid in moisture retention and to suppress weeds. Do not remove the fern-like top growth until it dies back naturally in the fall. After the asparagus has turned yellow to brown, cut back and remove the trimmings from the bed.
Harvesting Asparagus Plants
You can begin harvesting a moderate amount of hybrid asparagus during the season after planting for a 2 week period, choosing finger-size or larger diameter spears. (Open-pollinated varieties may require an extra year before you can begin harvesting.) The following season you can harvest for about 4 weeks, the third season for 6 to 8 weeks. From the 4th year on all stalks can be cut that are larger than pencil-size until about July 1, or when the spears begin to get thinner. Either snap or break the asparagus spears at ground level or cut the spears 1 inch below the soil surface.
Asparagus needs a lot of fertilizer. Very early each spring add more compost or aged manure to your asparagus bed. In addition, fortify the soil with a light handful of 5-10-10 or 10-10-10 fertilizer around each asparagus crown. Avoid high nitrogen fertilizers as they throw off the fern-to-root balance in the plant, and avoid hot manures such as hog, sheep or poultry. Bone meal and high calcium dolmitic limestone are often recommended. Asparagus also likes plenty of moisture. Yields will improve if steady soil moisture levels are maintained. A drip or trickle irrigation system is ideal for asparagus beds. Mulching reduces weeding chores by controlling weed seed emergence and helps to improve the soil by slowly adding organic matter as it breaks down. Mulch also protects asparagus spears if frost occurs during early spear emergence. A loose mulch layer of 4 to 6 inches of leaves or straw is preferred to a heavy material that could smother and prevent spear growth. Be diligent in keeping the asparagus bed free of weeds as they compete for nutrients and can mat the soil surface.
With a little care and by following these general guidelines, you will enjoy fresh asparagus from your planting for many years.