Asparagus is a long-lived cool-climate perennial that is high in a plethora of vitamins and minerals while being low in calories. It can adapt to all but the hottest areas of the South, but does especially well in zones 3 through 7. Zones 8b or higher have too mild of winters and the plants don’t go completely dormant. They cannot thrive in mild winter climates.
Usually only young asparagus shoots are eaten, as once the buds begin to open, the shoots turn woody very quickly. You’ll want to situate your asparagus patch where the growing fronds will not shade out your other vegetables but still be in direct sunlight. In addition, the site you choose should be somewhat protected from the wind so that the tall fronds do not blow over.
It will be several years before you’ll be able to harvest the first spear, but once the plants are established, they’ll be around for about 15 to 20 years.
Start preparing your soil about a year in advance of your planting. Asparagus needs soil that is well-drained with a pH between 6.5 and 7.5. If the pH is below 6.0, amend your soil with lime. Deep, fertile sandy loam is best for planting asparagus in, and if your soil has a more clay-like consistency, you’ll need to add peat moss to the dirt. The dirt should be loose about 12 inches down, and you’ll need to turn in about a 1-to-2 inch layer of compost into your asparagus bed. You can also use green manure crops, animal manure, and straw to build up the soil as well. Your dirt should be free of perennial broadleaf weeds and nutgrass.
When to Plant
Plant asparagus seed after all danger of a hard freeze is past. The ground needs to be warm enough for the seed to germinate. To speed up the germination process, soak your seeds in water for a few hours before planting. You can also start your seed indoors and set out the seedlings when they are 12 to 14 weeks old. Time it to transplant them just after your last spring frost.
How to Plant
Sow your seed in thin trenches that are a depth of about 2 to 4 inches if you live in a warm climate. If you are seeding or transplanting seedlings in a cold climate (zone 6 or below), dig your trench deeper, about 8 to 12 inches. Each row should be at minimum 12 to 18 inches apart in cooler weather areas. In areas of high humidity, you’ll want your rows further apart for better air circulation and to avoid disease problems. Rows as far apart as 5 feet have been recommended for high humid areas such as those found in the Deep South. Cover with 1 to 2 inches of soil and water your seeds in well. As the plants grow over the next weeks, push more dirt into the trench until you eventually get the dirt in the trench level with the surrounding soil. Do not completely cover the growing plants, however.
Your asparagus will begin emerging within 3 weeks from seed. You won’t attempt to harvest any of your asparagus the first year. You will also be on the lookout for the female asparagus plants that put their energy into berry production – and kill them. Unlike many other plants, you don’t need a male and a female to produce a crop of asparagus. Unless you’re trying to grow some of your asparagus for seed, the female plants are worthless. The male plants put their energy into root production, and it’s from the roots that your spears appear in the spring. Amish farmers are famous for the size of their asparagus crops and this is the lesson they learned long ago.
Caring for Your Asparagus
You’ll want to suppress weeds as much as possible while the stand becomes established. Hand weeding is best as using tools while your plants are at a young stage can damage the emerging root systems. A permanent mulch will help retard weed growth and retain moisture for your plants. A 2-inch layer of chopped leaves or finely shredded bark is recommended.
You’ll want to fertilize your asparagus in the late spring or early summer, after the harvest ends, in order to stimulate fern growth. These fronds feed the crown throughout the harvest, which can lengthen the harvest period when you begin harvesting your spears. You can side-dress with compost or an organic fertilizer. Once the soil freezes in winter and the foliage yellows, cut them back to about 12 inches and pull out any rotting stems the following spring.
In the South and far West, you can harvest your first spears one year after planting, but it’s best to wait at least two years if you live in the North. In the first year, harvest for about two weeks and then quit. The following year harvest about four weeks, and the year after that, six to eight weeks. Cut your spears before the buds start to open, when the spear is 6 to 10 inches in length. Harvest every other day, and if the temperatures are above 85 degrees, harvest daily. End the harvest when about three-quarters of your crop are the thickness of a pencil or less.
Asparagus beetles chew the spears and foliage. You’ll need to hand pick them off and kill them. Beetles can overwinter under mulch, so delay your mulching until late fall. Plant nectar-producing flowers near your asparagus to attract beneficial insects to protect your crop.
Asparagus rust or needle blight can make the needles turn yellow and drop. Cut and destroy the affected parts of the plant. Plant your asparagus far enough apart to help prevent diseases.
If new growth is stunted or bushy, you may have asparagus aphids. Natural predators are wasps and ladybugs. If the problem becomes severe, the application of insecticidal soap may be necessary.