Asparagus grows well at elevations up to 5,500 feet in Montana. It requires very moist soil and needs a fairly sunny area and does better in full sun. It takes at least three years to establish a good hill of asparagus in good production. Yield can be up to 2,000 pounds per acre when a bed is at its “peak”. However, seven or eight years may be required to bring it to “peak” production. If properly managed, a bed will last 12 to 15 years. Some over 30 years old are still good. Fortunately, asparagus will tolerate more salinity than other garden plants except garden beets, spinach and swiss chard. Therefore, low, wet areas where most other crops will not grow could be favorable for asparagus.
Establishing A Bed
Stock. There are three ways to start a new bed: 1. Buy one-year-old transplants 2. Direct seeding. 3. Dig up an old hill or clump of asparagus, divide the crown leaving one bud per division and set them out. An old clump could possibly be divided into as many as 50 new plants.
Soil Preparation. Destroy all perennial weeds by mulching, cultivation or spraying. Then spade or plow the soil deeply to pulverize it well. If available, you can work in from 1/2 to 1 pound of well-decomposed organic matter per square foot. If fresh or high nitrogenous manure(s) is used, apply only about 1/8 to 1/4 pound per square foot. Like most plants, asparagus uses nitrogen, phosphorus, potassium, calcium and other minerals. If needed, fertilizer should be applied at planting time (see “Maintaining Established Beds” side 2). Most soils in Montana contain adequate calcium. However, acid soils in the high mountain valleys and some real sandy soils in other areas may need some calcium. It can be supplied with wood ashes, lime and gypsum.
Planting. After soil preparation, dig round holes about 10 inches deep and 10 to 12 inches in diameter. Place a young transplant into each hole with the central bud pointing upward. Cover the young transplant with about 3 inches of topsoil. As the young, green shoots emerge from the bud and extend above the 3 inches of topsoil, continue to fill the hole. When the tip of the shoot extends above the ground level, complete filling the hole.
Spacing. A healthy asparagus hill will occupy from 6 to 10 square feet of space. If between-row spacing is 3 feet, allow about 2 1/2 feet of space between hills. To accommodate machinery or to drive a tractor between rows will require as much as 6 feet between rows. To control spacing in older beds, see “Maintaining Established Beds” side 2. Keep the new asparagus bed watered well, control weeds and guard against insects.
Perhaps the most tried and proven variety is Mary Washington. It yields well, survives well and is resistant to rust disease. Other varieties which can be grown in Montana include Martha Washington and Jersey Giant. Both of these varieties are rust resistant.
Several weed control chemicals are used in commercial asparagus fields. However, they should not be used or used only with great caution in home gardens and lawns. Some weeds can be controlled early in the spring before spears come up by hoeing or by very shallow tilling. Later, after the cutting season, broadleaved weeds may be controlled by spraying with the sodium salt form of 2, 4-D at a rate of 3/4 ounce per 1,000 square feet. Be sure it does not drift onto any nearby wanted plants.
Asparagus Beetle. This insect resembles a ladybug but is considerably more elongate. When uncontrolled they defoliate large areas in a short time. Spray or dust with Sevin, Rotenone, Malathion or any legal insecticide locally available.
Cutworms. Cutworms cut off shoots underground and also feed on tips of shoots causing crooked spears. Remove injured spears, dig underneath and destroy the worm. Dust spears with Rotenone, but be sure to wash them well if harvested later.
This disease is found more in high rainfall and humid areas and less in dry or arid and semi-arid regions. Nevertheless, it has been seen in Montana. Symptoms are small, reddish-yellow spots on the main stem near the ground, and on the slender branches of the stalks which grow up after the cutting season. Tiny needle-like balls give the plant a node-like appearance. To avoid this, plant resistant varieties. The most well-known, rust resistant varieties are Mary Washington and Jersey Giant.
Harvest time varies from season to season and from area to area. In an early spring in warmer areas or lower elevations, spears may be ready as early as late April. Conversely, higher areas in a cool spring may not have spears for harvest before mid-June or later. Harvest can last up to July 1, but not in every area every year. Spears are ready to cut when they are 8 to 10 inches tall. If cut too soon the yield will be less. If cut too late, spears will be large and tough. Avoid Over-Harvest! No hill of asparagus will last very long if all spears are taken. It is necessary to leave two or three spears per hill to grow until winter to build up a vigorous root system. Without a good root system there will be few or no spears the following spring. So, avoid over-harvest.
Maintaining Established Beds
After three years the new bed should be yielding spears for harvest and a few to leave to build up a good root system.
Fertilizer. Water and minerals used by the plants will need replenishing. Unless the soil is high in organic matter, it will be necessary to apply nitrogen annually at the rate of 1 to 2 1/2 pounds of actual nitrogen per 1,000 square feet. Apply it early in the spring. Every three to five years apply 2 to 3 1/2 pounds of actual phosphate per 1,000 square feet and spade or work it down between hills. If the soil is deficient in potash, then apply it at the same rates and about the same time intervals as for the phosphate.
Mulching. It will help to apply an insulating or shading type mulch in late November. Straw or any similar material is good. Chopped or shredded asparagus stalks spread over the bed will make good mulch. In the early spring remove the mulch. If left on, it will keep the ground cool, delaying emergence of spears. This is especially important in cool mountain valleys. Asparagus hills extend roots and crowns horizontally. This makes it difficult to keep the hills in a straight line. Whenever there are spears off the row harvest all of them, leaving more spears on the row.