Monday, January 21, 2013

How to Grow Asparagus in the North

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Asparagus grows great in areas with cold climates and those on the drier side where the crop can over winter without getting saturated making this a great vegetable to grow in the north. Wherever you choose to put your asparagus bed, make sure it’s in a spot that can be dedicated to growing this vegetable for years to come as spears reemerge for up to 15 to 20 years.

In this guide you’ll find how to grow asparagus from crowns and seed, how to prepare and maintain the bed, growing, weeding, watering and mulching instructions, when and how to harvest, how to control disease and pest infestations and types and varieties of asparagus.

Plant Type: Perennial
Genus: Lily Family
Name: Asparagus Officinalis

Guide to Growing Asparagus

How to Grow Asparagus from Crowns

Where to Plant: Full sun in light, well-drained soil to prevent root rot.

Preparing the Bed: Remove all roots and other debris from the soil. Add 1-2 inches of year-old manure and finished compost, tilling it well into the soil. This will provide  crowns with plenty of nutrients to get off to a healthy start.

Planting Instructions: Dig trenches 12 inches wide and 6 inches deep. Place each crown in the trenches so they are 1.5-2 feet apart. Cover each crown with 2-3 inches of soil. Water. Wait 2 weeks and add another layer of soil, 1-2 inches deep. Repeat as soil settles and forms a slight bump over crowns. The bed will defer in size depending on how many crowns are planted.

Mulching: Add a layer of mulch to the asparagus bed after planting. Mulch should be 2-4 inches deep to prevent weeds from growing and to retain moisture. 

Weeding: Pull all weeds because they will steal nutrients and water, especially from young asparagus shoots. 

Watering: It’s critical to water asparagus during the first 2 years after planting when plants are still maturing. Water on an as needed basis keeping the moist but not saturated. Water in early mornings to help prevent rust. 

Over-Wintering Instructions: Do not cut back asparagus stalks. Lightly mulch the bed with straw or preferred mulch to offer over-wintering protection. In the spring, remove the ferns. 

Starting Asparagus from Seed

When: Start seeds indoors from February to March.

Sowing Instructions: Soak asparagus seeds in water for a few hours before sowing. Using paper pots, fill ¾ of the way with light potting soil mixed with compost. Sow 1 seed per pot. Keep pots in a warm room, around 60°F. When sprouts appear, move pots to a location filled with natural light but keep out of direct sunlight. Once all danger of frost is gone, begin hardening off asparagus seedlings. Follow above planting instructions when seedlings are ready to be moved to the bed.

How to Harvest Asparagus

Do not harvest for the first 2 years after planting unless otherwise noted on the variety planted. During this time, asparagus needs to establish its root system in order for productive yields to grow for years to come. 

During the 3rd year, harvest only during a 4 week period. During the 4th year, extend the harvest over 8 weeks. Begin harvest in early summer, harvesting about every 3 days. Using a sharp knife, cleanly slice spears just below the ground’s surface. Harvest while spears are at desired diameter, are about 8 inches tall and have tight heads. Spears that have over-matured become tough and woody. 

Disease and Pest Control

Rust is a common disease effecting some varieties of asparagus. Many newer hybrid varieties such as Jersey Night Hybrid, Jersey Giant and Martha Washington are bred to resist rust. Opt for a resistant variety before planting. If rust does occur, red and brown spots will be noticeable on the leaves and stems of plants.

To combat this problem, remove affected stocks to keep from spreading, and burn or bag them to toss out with the trash. Remove all dead plant debris from the bed. Follow the correct growing instructions such as planting in well-drained soil, spacing guidelines and watering in early mornings to further prevent rust. 

Fusarium wilt is another disease prone to showing up in asparagus beds. If plants yellow or brown and become wilted or die, Fusarium wilt is most likely present. Signs that Fusarium wilt is present include reddish-brown lesions on stems and rotting crowns. This disease weakens plants over time, slowly killing them off. 

To prevent Fusarium wilt, do not plant a new bed where an old one existed for at least five years and opt for a wilt resistant variety. (Jersey Giant is both rust and Fusarium wilt resistant). Do not over harvest which will weaken the plants. Water, weed and fertilize as necessary. 

Prevent root rot by planting in well-drained soil, preferably in raised beds. Make sure not to saturate the bed when watering. If heavy frost is an issue, cover plants with straw mulch or newspaper as a layer of protection. The most common sign of damage as a result of frost are brown, withered stalks. 

Types of Asparagus 

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Green: Green asparagus is the most common type seen in produce sections. It is less fibrous than purple varieties and slightly thinner. They get their green color through the photosynthesis process.


Purple: Purple asparagus is sweeter and slightly thicker than green and white varieties. It gets its color from the high levels of anthocyanins in the plant which are high in antioxidants. 

White: White asparagus is very similar to green varieties in taste, texture and size. It gets its white color from growing in the dark where it cannot photosynthesize. White varieties are typically more expensive to buy than other types because of its limited supply. 

Varieties of Asparagus to Grow

Asparagus produce both male and female plants, making it a monoecious vegetable. Male plants produce higher yields, but both male and female plants will produce tender stalks.

Jersey Knight Asparagus Hybrid 

Jersey Knight
Produces high-yields from 99.5% all male plants. Spears grow to 5/8 inches in diameter with bright green stalks and dark purple tops and bracts. Plants grow 24 inches to 5 feet tall. Zones 2-8. Resists Crown Rot and Rust. Disease Resistant. Harvest in early summer.

Purple Passion Asparagus

Purple Passion
Produces medium yields. Grows sweet, tender, purple spears. Spears grow to .5 inches in diameter and 3-5 feet tall. Zones 2-8. Disease resistant. Harvest from early to mid summer. 

Jersey Supreme Hybrid Asparagus

Jersey Supreme
Produces high yields of 10 pound crops each year from all male plants. Grows mid-size succulent spears which are ready for harvest the second year after planting. Zones 2-9. Adapts easily to stress, drought and cold. 

Jersey Giant Hybrid 

Produces high yields of male plants only. Plants grow up to 12 inches tall and are very tasty. Resists rust. Ready to harvest after 3 years. 

Mary Washington Asparagus

Spears are green with purple tips. Plants grow up to 12 inches tall. Ready for harvest after 3 years.

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