Unlike most vegetables, asparagus plants are perennial, which means the same plants grow in your garden year after year. The spears that we enjoy as a vegetable are the new shoots that emerge in spring. The most important part of growing asparagus is to realize that it will take a couple of seasons before you taste the first bite of homegrown asparagus. Plants need to be allowed to mature before you can harvest. They will remain in the same place in your garden for many years—15, 20, sometimes 30. In fact, a productive asparagus bed is a good reason to renovate your house, rather than move!
Asparagus can be grown in most parts of the country, but does especially well in cooler regions with longer, colder winters. These periods of dormancy allow asparagus stalks to grow more robustly in the spring than they do in warmer regions with milder winters.
How much your family enjoys asparagus determines how many plants you will need. A good start is 10 plants for each person. If it is a family favorite or you plan to freeze some for later, you will need more.
Soil, Planting, and Care
The key to growing asparagus is to have healthy, vigorous plants that produce a lot of spears. Choose a sunny, well-drained site on the edge of your garden where it will not be disturbed by the activity of planting and re-planting other areas.
Planting asparagus is like preparing for a trip. Careful preparation makes the journey easier. It is the same with asparagus. Before you buy the plants, you need a prepared bed. Hopefully this is the only time you’ll plant asparagus. How well you prepare the bed determines the vigor of your asparagus patch for years to come.
Space plants 12 to 18 inches apart. If there are tenacious weeds or grass, treat with an herbicide for use with food crops, or cover the area with black plastic during the summer before planting to eliminate problems in the future.
In autumn, prepare the soil by mixing in several inches of organic matter (think compost or aged leaves) or Miracle-Gro® Garden Soil for Vegetables & Herbs with the native soil in each row. Have your soil tested and amend it with lime if the pH is below 6.0 to 6.5. Add any other nutrients as recommended on test results. Mulch for the winter, or grow a cool season cover crop that can be turned under before planting in spring.
In spring after danger of frost has passed, dig a depression 6 to 8 inches deep running the length of the row, mounding the amended soil on each side for later use. Set seedlings into lowest part of the depression, planting about 2 inches deeper than they were originally growing. Space plants 12 to 18 inches apart.
Feed plants with Miracle-Gro® Shake ‘n Feed® Tomato, Fruit & Vegetable Plant Food at planting and every 3 months during the growing season, following the directions on the label.
As plants grow taller, rake a little of the soil on the edge of the row into the depression where plants are growing. Soon the bed will be level. Mulch to prevent weeds.
Then all you need to do is be patient. The ideal is to wait at least 2 seasons and probably 3 before harvesting. It may be hard to resist tasting the first spears to emerge, but go easy on the plants until they mature. You’ll be rewarded in the long run!
Bent spears are caused by insects feeding or damage from cutting adjacent stalks. The damaged stalk grows normally on the side away from the wound, causing the spear to bend.
A well-drained bed will have minimal disease problems. Black and red asparagus beetles can be a challenge, damaging the foliage and weakening the roots. Usually you can control them with hand picking. Just drop them into a bucket of soapy water.
Harvest and Storage
Once asparagus plants are strong enough to be harvested, cut all new shoots in spring when they are about 8 inches tall, snapping them off at the soil line. Many seasoned gardeners use a knife to cut below the soil line, but it is important to avoid cutting into emerging spears nearby. Also, the knife can spread any disease from one plant to the next.
Remember, if the spear has begun opening and developing foliage, it will be too tough to eat. To avoid this happening, plan to harvest at least every other day. Go ahead and pick all the spears each time you harvest. Discard those that have grown too large.
The duration of your harvest will depend on the vigor of your plants. If your plants are young, the fresh asparagus season may last a couple of weeks. However, established plants can produce much longer, as much as 8 weeks. The old rule of thumb is to harvest until the diameter of the spear decreases to the size of a pencil. Then it is time to stop and let them grow, gaining strength for next spring.
Cook cut spears immediately or refrigerate in plastic to raise the humidity and prevent tough fibers from forming at the base of the spear. These fibers form as a result of the injury of cutting. That’s why spears from the grocery store or from the refrigerator should always be trimmed to remove any tough tissue before cooking.
Fresh asparagus spears can be stored a week or more. If you want to put some aside to enjoy in the months to come, blanch them in boiling water for 3 to 5 minutes, douse in cold water, wrap, and freeze.
Cut back the 4 to 6 foot tall foliage, or the ferns as they are called, after frost has turned them brown. This is a good time to control weeds because the asparagus are dormant. Keeping the bed weed free is important to avoid competition with your asparagus plants. Because the soil is so rich, invaders can take hold quickly.