• Increase your garden's output by including perennial vegetables like asparagus.Minispargel image by Yvonne Bogdanski from Fotolia.com
  
  Most food crops grown by home gardeners are annuals, but several interesting vegetables are perennial plants, meaning they keep producing year after year without replanting. These plants require a site that can remain undisturbed for years and good soil preparation to produce well.
  
  

Asparagus

• Asparagus is an early spring vegetable.asparagus stems image by paul mitchell from Fotolia.com
  
  Asparagus is one of the earliest and most prized spring crops. A well-maintained asparagus bed can produce for 20 years or longer. Choose a spot in full sun for best production. Prepare the bed by loosening the soil 8 to 10 inches deep and wide, and incorporate plenty of organic material. Purchase large plant crowns in spring and plant as soon as possible. Spread roots in a trench 6 to 8 inches deep and 18 inches apart. Cover with 2 inches of soil to start; gradually cover with more soil as they grow. Don't harvest until two years after planting, and only take a light cutting that first year. Asparagus spears are ready to harvest when they're 6 to 8 inches long. Leave the ferny tops until they have browned on their own. Side dressing plants with regular applications of compost or manure ensures vigorous growth.
  
  

Rhubarb

• Rhubarb requires some frost in winter to produce the best stalks.rhubarb image by Alison Bowden from Fotolia.com
  
  Rhubarb's reddish leaf stalks add tartness to pies and jams, and are a traditional companion to strawberries. The leaves are poisonous and must be discarded. Plant rhubarb 1 to 3 inches deep and 3 to 4 feet apart in late winter or early spring and let them grow undisturbed for two years before harvesting. Choose a spot with rich, well-drained soil in full sun and keep the plants well watered. They can tolerate frost in spring but a hard freeze will damage the emerging leaves, so cover.
  
  

Artichokes

• Artichokes are large, impressive plants.Artichokes image by Laura Benson from Fotolia.com
  
  Prized for their delicious hearts, artichokes are a challenging vegetable to cultivate. They require full sun and well-drained, organic soil. They also need heavy feeding with a low-nitrogen fertilizer and heavy watering to perform well. Plants are 3 to 6 feet tall and 2 to 4 feet wide. They're sometimes grown as an ornamental plant in areas where they're not hardy, as their flower resembles a large thistle. They can withstand a light fall frost but a heavy frost or freeze will damage production. Plants may last up to 15 years but production is best if divided every three or four years. Mulch heavily with leaves for winter protection in their northern range.
  
  

Egyptian or Walking Onions

• Egyptian or walking onions are similar to shallots, but stronger flavored. They need full sun or light shade and well-drained soil, as well as even, plentiful watering for good yields. The plant produces many bulbs below ground, as well as clusters of sets (baby onions) on the stalk. You can increase your planting by division in late summer or by planting the sets from the stalk. Cornell University recommends division every three years. Egyptian onions should be mulched in winter to prevent frost heaving.