Unlike most vegetables, asparagus is a perennial, meaning it lives for more than two seasons. It takes a couple of years to mature before you can harvest and enjoy it, but it lasts for many years. Asparagus stalks increase in circumference and number over time — it definitely gets better with age.
1. Understand the life cycle of the asparagus plant
Asparagus roots produce individual stalks above ground. When the stalks are harvested in the spring, this depletes the energy from the roots. After a period of harvesting, it’s important to allow stalks to develop into ferns. A vigorous and healthy fern in the summer helps ensure a good asparagus harvest the next spring. The photosynthesis that takes place in the ferns throughout the summer replenishes the energy of the depleted roots. The ferns go dormant in winter and turn yellow — at this point they can be cut back. In the spring, shoots appear from the overwintering roots. These stalks grow larger in circumference every year as their life cycle continues. Asparagus roots produce for 10 to 12 years. After this time, the plant is spent and should be replaced.
2. Decide on the location to plant asparagus
Because asparagus plants produce for several years, they require a dedicated bed for that period of time. Choose a location that gets at least 6 hours of sun a day. Avoid windy areas and areas where water puddles. Consider using raised beds because asparagus roots become soggy and will rot in clay soil. Asparagus needs rich, well-amended soil that is high in phosphate. A 5 foot by 5 foot bed is a good size and provides plentiful harvests of asparagus.
3. Decide whether to plant asparagus crowns, seeds or starts
It’s easiest to establish asparagus by planting one to two year old crowns. They produce harvestable stalks about a year after planting. Asparagus can also be planted from seed. This method is cheaper, but it requires a two year wait and more care for the emerging seeds. However, asparagus from seed often produce more than those started from crowns. You may also find transplants started from seed at your local nursery.
4. Plant asparagus correctly
In the low desert of Arizona plant asparagus transplants from November through the first half of February. Check local planting guides for the correct time to plant in your zone. Prepare the asparagus bed by adding large amounts of compost, composted manure, and mulch to create rich soil. If planting from seed, start seeds outdoors in small pots with quality, fine soil. Sow seeds ½ inch deep. Germination takes about 30 days. Transplant plants to the permanent bed when plants are 3 inches tall.
To plant from crowns, dig a 6 inch trench, and place dormant roots in it about 12 inches apart. Cover crowns with about 2 inches of soil, and gently tamp it down. Continue adding 2 inches of soil every 2 weeks until the trenches are filled with soil and slightly mounded on top.
5. Harvest asparagus at the right time
For the first year after planting (two if started from seed), do not cut or harvest any stalks. Allow the stalks to go dormant in the fall and cut back watering or stop completely. New spears begin to emerge the following spring, and you can harvest any that are at least ¼ inch in diameter. Let smaller stalks grow through the summer to give energy to the roots.
For subsequent years, observe these practices for healthy and productive plants
Dry dormancy. Cut back dry stalks and amend with 6 inch layer of compost.
Harvest stalks that are more than ¼ inch in diameter for 4-6 weeks. Let smaller ones continue to grow.
Amend spent bed with another 6 inch layer of compost.
Summer / Fall
Water them and do not let dry out. Allow ferns to grow and provide energy for roots.
Ferns will begin to turn yellow. Cut back watering and allow to go dormant.
6. Harvest asparagus correctly
Harvest spears when they are 6 to 10 inches high and the tips are firm and tight. Do not harvest spears smaller than ¼ inch thick, and do not harvest the first year. The following year, harvest for 2 weeks. Extend the harvest each year by 2 weeks until you are harvesting for 6 weeks. Pick asparagus every 3 days, more often in warm weather. Pick asparagus by snapping off at ground level with your thumb and index finger. You can also cut off just below soil surface with an asparagus knife or other sharp knife. Asparagus is delicious eaten fresh in the garden. Eat or preserve it as soon as possible after picking. You can also store stalks upright in a small amount of water in the refrigerator for several days.