Asparagus is one of the few perennial vegetable crops. The shoots are picked as young spears, in the spring. Later in the season the foliage matures into an airy, fern-like cloud which changes to a golden color in the fall. Because asparagus takes up a permanent place in the garden, but can be an attractive plant, many people with space imitations use asparagus as a border or hedge plant.
Asparagus spears are straight shoots with scale-like tips. Although green varieties are most commonly grown, there are also many purple varieties. White asparagus is blanched, to prevent photosynthesis.
Shoots continue emerging from the soil throughout the spring. As the weather warms, the shoots will begin to get spindly. At this point, they are left to grow into the mature ferny foliage, which feeds the roots for next year's crop. Asparagus plants can continue producing for 20 years or more.
Common Name(s): Asparagus
Asparagus does well in USDA Hardiness Zones 4 - 9.
Exposure: Asparagus grows best in full sun. Without enough daily sunlight, you will wind up with thin spears and weak plants.
Mature Size: The spears only get 6 - 8 inches long, but the mature plants will grow approximately 5 ft. tall x 3 ft. wide
Days to Harvest:
Expect to harvest from mid-Spring through early summer, depending on the climate and weather.
Since you won't be harvesting for the first year or so, asparagus requires some patience, but it's worth it. Once your plants are established, you'll be harvesting for months. Asparagus is a spring vegetable, preferring cooler temperatures and full sun.
Soil: Since asparagus is a long-lived perennial, it pays to take the time to improve your soil before your plant it. Work in plenty of organic matter and make sure the soil pH is in the neutral 6.0 - 7.0 range.
Planting: Plants can be started from seed about 4 weeks before the last expected frost. Seeds will add several years to your wait and asparagus is more commonly grown from crowns, which are the one year old base and roots of the plants. They look like a worn out string mop, but they are very much alive.
The crowns will need to be covered as they grow. The most common way to plant asparagus crowns is in a trench. In the spring, dig a trench about 8-10 in. deep and 18-20 in. wide. Work in your compost or other organic matter at this time.
To plant the crowns, spread the roots of the crowns out on the bottom of the trench. Space plants about 12-15 in. apart, so they will have room to grow. Cover with a couple of inches of soil and water well.
As the plants begin to grow, continue covering them with soil, leaving only a few inches exposed above ground. Do this until the trench is full.
Water regularly, especially while young. It takes about three years for plants to mature enough for harvesting. Prior to that plants should be allowed to grow and feed themselves.
Top dress annually with compost or mulch. You can do this in early spring or in the fall, after the fronds have died back and been cut to the ground. Keep the patch free of competing weeds.
The plants will need to be cut to the ground each year, before new growth starts. You can do this in spring, but I prefer the fall. Removing the dead foliage in the fall prevents problems, like asparagus beetles, from over-wintering. However other gardeners like to leave the foliage as a winter mulch.
Asparagus does not have too many problems. Fusarium wilt can be a problem with older varieties, but you can avoid it by planting resistant varieties.
The biggest pest is the asparagus beetle. Keep watch for them and hand pick the eggs, when there are only a few. Otherwise neem should keep them under control.
You can harvest a few spears in the second year of growth. The plants are not really mature, so let them grow after that initial treat.
In the third year, begin harvesting spears that are finger-sized and about 8" long. You can either snap off the spears or cut them with a knife, just below the soil line. If you use a knife, be careful you don't also slice the later shoots that haven't poked through yet.
Harvest for about 4 weeks the first year. In subsequent years you can harvest until the weather warms and the spears look spindly. Then allow the foliage to grow and feed the plants.
It's hard to find a bad asparagus variety, but the newer cultivars were bred to be all male, so they put all their energy into growing spears, not seed. Most were bred in New Jersey and any variety with New Jessey in its name is probably one of these.
Some popular choices:
- Mary Washington is the most commonly found variety. It was bred for rust resistance.
- Jersey Giant is rust and fusarium wilt resistant and yields early.
- Brock Imperial offers high yields.
- Princeville does well in warmer climates.
- Purple Passion is a sweet purple variety.