by Emma Cooper

Created on: August 25, 2007   Last Updated: February 23, 2011

Botanically-speaking a perennial plant is one that keeps growing from year to year, unlike annuals or biennials that complete their lifecycle in one or two years and then die. In kitchen garden terms, a perennial is a plant that is allowed to keep growing. Many familiar kitchen garden plants are treated as annuals for simplicity, and many more would be perennial in a different climate.

Having a larger number of perennial plants in your kitchen garden can cut down on the work load - you'll have a smaller area to replant each spring, and established perennial plants can be much more drought-tolerant than their annual relatives. But perennial plants aren't necessarily well-behaved. Some are rampant thugs that will take over your garden if you give them the chance.

Gardeners with an herb bed will already be familiar with many of the culinary perennial plants: mints, rosemary, thyme, lemon balm and many other herbs live for several years. Try adding in a few of the more unusual herbs; Good King Henry provides salad leaves all year round and sorrel can be used in many dishes for a lemony kick and makes a lovely soup.

A clump of perennial onions would be at home in the herb garden or a vegetable bed. There are several to choose from, all of which add interest to the garden. The Welsh onion, for example, has large white flower heads that are loved by bees (although you'll need to remove them before they set seed if you don't want onion seedlings all over the garden!). Welsh onion leaves can be used like chives, or you can dig up and divide the clump and use the whole onion like salad onions. The Egyptian (or Walking) onion doesn't produce flowers. It reproduces by growing small bulbs at the top of the stalk. When the bulbs get too heavy, the stalk bends to the ground and plant the new bulbs and so the clump gradually spreads across the garden.

Well-known perennial vegetables include asparagus and globe artichokes. Although the asparagus season is short, many people give it room in their kitchen garden because the taste of home-grown asparagus is so divine. Globe artichokes are stunning plants, but they do need a lot of room. Jerusalem artichokes are from a different plant family, and produce edible tubers that are in season in the winter when other goodies from the garden may be in short supply. They are very easy to grow and, like potatoes, they will re-grow from any tubers left in the ground. They can become invasive, but should be easy enough to keep under control.

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