Asparagus is a perennial vegetable plant that can be a long-lasting, permanent addition to a home garden. This vegetable requires well-draining soil to thrive; waterlogged soil can cause the roots of the asparagus plant to rot. Growing asparagus in raised beds offers them well-draining soil, as well as being a more convenient way to plant asparagus, since it does not require that you till the soil deeply with a rotary tiller.
Prepare the raised bed in advance before the last frost of the season ends. Place the raised bed in a sunny location of the yard that receives six to eight hours of sunlight daily. Asparagus plants can tolerate some light shade. It is best to have a raised bed that is at least 12 inches in height to accommodate the growing root systems of the asparagus plants.
Fill the raised bed with good-quality topsoil that is blended with compost or other organic matter such as manure or peat moss. Lay black plastic over the entire raised bed, covering the soil. This will help to retain heat within the soil for an early spring planting.
Purchase 1-year-old asparagus crowns. Ensure the asparagus crowns you purchase are healthy and male. Female asparagus use too much energy on producing seeds, leaving a less-than-desirable crop production.
Remove the black plastic when the last frost date has passed. Dig trenches 6 inches deep and 5 feet apart with a garden trowel. Sprinkle 1 lb. of triple superphosphate (0-46-0) for every 50 feet of soil into the trenches.
Soak the asparagus crowns in a bucket filled with warm water for one hour.
Set the asparagus crowns into the dug trenches, spaced 12 inches apart. Fill the trenches in with the dirt that you removed earlier to cover the asparagus crowns.
Water the asparagus crowns until the soil is moist, without becoming oversaturated. Continue to water once or twice per week to keep the soil moist.
Spread 2 to 3 inches of peat moss throughout the asparagus bed when the tips begin to emerge from the soil, usually in one to two weeks. The peat moss aids the soil in retaining more moisture and acts as a weed barrier within the asparagus' raised bed.
Pick weeds out of the asparagus bed regularly by hand. Keeping the asparagus garden weed-free eliminates competition for nutrition and water, allowing the asparagus to produce an abundant crop in the next growing season.
Harvest a few asparagus spears when the plants are in their second growing season, and have reached heights between 7 and 9 inches tall. Cut the spears off the plant at soil level with a sharp knife. Leave half of the asparagus spears on the plant to provide energy for the third season's crop.