The list of vegetables that are true perennials is short: rhubarb and asparagus return year after year, while artichokes and sorrel may also act as perennials. While the tendency of a vegetable like asparagus to come back after a harsh winter is something to be celebrated, this growing habit also means that we must sometimes move asparagus from its original planting bed to a new site in the garden. Learn the how and when of transplanting asparagus to bring the spears of spring to your plate for many years to come.
Why Transplant Asparagus?
Asparagus plants are long-lived and vigorous. When asparagus plants are growing in a sunny site with good drainage, proper irrigation, and adequate nutrients, the plants multiply and become crowded over time. A mature stand of asparagus plants produces spears over several weeks, and even up to eight weeks. During this time, a healthy plant should produce around 20 spears. If you notice a decline rather than in increase in your harvest from the past growing season, the plants may be too crowded, leading to a reduction in vigor.
Another reason to transplant asparagus is to move asparagus plants to a site that will increase their ability to thrive. Because they are so long-lived, sometimes a site that was good several years ago loses its viability. For example, a young tree matures and casts shade that wasn't there before, or a new garden shed or other structure overshadows the bed. Finally, you might need to transplant asparagus from a friend's garden to yours, or vice versa. The ability of asparagus plants to multiply means that sharing the bounty is part of the fun of growing this perennial vegetable.
When to Transplant Asparagus
Asparagus enters a period of rapid growth during the spring. During this period, the plants are better able to renew themselves and repair any damage sustained during digging and transplanting. The exact timing depends on your climate and the weather, but early spring, as soon as the ground can be worked, is the right time to begin the transplanting process.
How to Dig Asparagus for Transplanting
Before you dig your asparagus, you must prepare the new site for planting. This is to minimize the time your dug plants spend above ground. Dig a generous amount of compost into the new planting site. Check the soil pH; it should be close to neutral, about 6.5-7.5. Dig a trench about six inches deep, where you will place the transplants.
Now it's time to dig up the established plants. Dig deeply with a sharp spade. Cut into roots as needed to bring up manageable clumps to the soil surface. Shake soil from the clumps, or rinse them gently to expose the roots.
The Asparagus Dividing Process
Identify your asparagus crowns, which will delineate where to make your divisions. Each crown may have several whitish spears beginning to emerge. Roots may be very tangled, and you can tease them apart the best you can with your hands before using a sharp garden knife to separate them. If the roots are excessively tangled and overgrown, you can trim the root mass up to make them easier to replant.
Replanting Your Asparagus
Make a mound of soil mixed with compost in your prepared trench. Arrange the mounds so that each asparagus plant is about 18 inches apart. The top of the crown should be about two inches beneath the soil surface. Spread the roots of the plant over the mound, and make sure the emerging spears are facing upwards. Cover the crowns with the soil and compost mixture until the trench is filled in. Cover the soil surface with three inches of mulch. This will both stop weed seeds from germinating, and preserve moisture for the newly planted crowns.
Care for Newly Transplanted Asparagus Plants
Treat your newly divided and transplanted asparagus like a brand new planting. Asparagus beds should be moist, but not soggy. After the soil settles, fertilize the plants with an all-purpose balanced fertilizer. Apply one pound of granular fertilizer per 100 square feet. Keep your asparagus bed weeded by lightly cultivating around the plants. Skip the harvest on the new bed for the first season to help plants develop the energy to deliver many future productive years in your garden.