How To Grow Asparagus
To grow Asparagus plants may take 2 to 3 years to truly get started and produce, however, the plant can be productive up to 20 years, so your time and efforts will be worth it. Asparagus is a perennial that likes a sunny area of the garden. Regions with cool winters are best for this cool-season crop. Asparagus plants are monoecious, meaning there are male and female Asparagus plants, with the female plants producing berries.
Starting asparagus from 1-year-old crowns gives you a year’s head start over seed-grown plants. Two-year-old crowns are usually not a bargain. They tend to suffer more from transplant shock and won’t produce any faster than 1-year-old crowns. Buy crowns from a reputable nursery that sells fresh, firm, disease-free roots. Plant them immediately if possible; otherwise, wrap them in slightly damp sphagnum moss until you are ready to plant.
Asparagus is planted in early spring as soon as the soil can be worked. The plant is grown from “crowns” (1-year-old plants). Eliminate all weeds from the bed, digging it over and working in a 2- to 4-inch layer of compost, manure or soil mix. Dig trenches of about 6 inches wide and 6 to 12 inches deep. Some experts believe shallow trenches of 6 inches are best. Asparagus does not like to have its feet “wet,” so be sure your bed has good drainage. For that reason, raised beds can be a good place to plant asparagus. Learn how to make a raised garden bed.
Asparagus Companion Plants
Companions for asparagus must like sun exposure and be able to work around the semi-permanent asparagus. Companions for asparagus may be those that add nutrients to the soil, deter pests and disease, harbor beneficial insects, or aid in water retention or weed retardation. What Grows Well with Asparagus? Asparagus companion plants may be other veggie plants, herbs or flowering plants.
Asparagus gets along with many other plants, but tomatoes are notorious for being excellent asparagus plant companions. Tomatoes emit solanine, a chemical that repels asparagus beetles. In turn, asparagus gives off a chemical that deters nematodes. Planting parsley and basil, along with the tomatoes, in close proximity to asparagus is also said to repel asparagus beetle. Plant the parsley and basil underneath the asparagus and the tomatoes alongside the asparagus. The bonus is that the herbs help the tomatoes grow better. In this particular companion planting quartet, everyone is a winner. Other herbs that enjoy asparagus’ company include comfrey, coriander and dill. They repel insect pests like aphids, spider mites and other detrimental insects.
Early crops such as beets, lettuce and spinach can be planted between the asparagus rows in the spring. Then in the summer, plant a second crop of lettuce or spinach. The taller asparagus fronds will give these cool weather greens much needed shade from the sun.
During Colonial times, grapes were trellised between asparagus rows. Flowers that coexist well with asparagus include marigolds, nasturtiums and members of the Aster family. The most interesting combination of companion plants for asparagus that I have read about was asparagus, strawberries, rhubarb and horseradish.
What to Avoid Planting Next to Asparagus
Garlic and onions can be offensive to some people, and to asparagus. Keep them well away from asparagus in the garden. Potatoes are yet another crop that should maintain some distance. Cross check and be sure that all the asparagus companion plants are friendly with each other prior to planting, as some plants simply do not like one another.
Starting Asparagus From Seed
It takes patience to start your asparagus patch from seed, but there are advantages to gain from the extra wait. Seed-grown plants don’t suffer from transplant trauma like nursery-grown roots, and you can buy a whole packet of seed for the same price you’ll pay for one asparagus crown. Most seed-grown asparagus plants eventually out-produce those started from roots. Growing from seed also allows you to selectively discard female asparagus plants and plant an all-male bed, no matter what variety you choose to grow.
Check the Soil pH!
In the North, start seedlings indoors in late February or early March. Sow single seeds in newspaper pots, place the pots in a sunny window, and use bottom heat to maintain the temperature of the mix in the pots at 77°F. When the seeds sprout, lower the temperature to 60° to 70°F. Once the danger of frost is past, plant the seedlings (which should be about 1 foot tall) 2 to 3 inches deep in a nursery bed.
When tiny flowers appear, observe them with a magnifying glass. Female flowers have well-developed, three-lobed pistils; male blossoms are larger and longer than female flowers. Weed out all female plants. The following spring, transplant the males to the permanent bed.
Don’t harvest any asparagus spears during the first 2 years that plants are in the permanent bed. They need to put all their energy into establishing deep roots. During the third season, pick the spears over a 4-week period, and by the fourth year, extend your harvest to 8 weeks. In early spring, harvest spears every third day or so; as the weather warms, you might have to pick your asparagus twice a day to keep up with production. Cut asparagus spears with a sharp knife or snap off the spears at, or right below, ground level with your fingers.