Perennial vegetables deserve more attention than they normally receive. Just as fruit trees provide food year after year with relatively little work, perennial vegetables can do the same. Generally these plants need little attention once established and can be planted in any small spare space. Of course these plants are only useful if you like what they produce and actually eat them. If you don’t then they are just unusual and interesting ornamentals.
Quite a few perennial vegetables exist, but only asparagus, artichoke and rhubarb are grown with any regularity. Garlic, leek, and potato are actually perennial too, though we grow them like annuals).
Perennial vegetables are not a substitute for annual crops, but provide another layer of low-maintenance crops that supplement the annual vegetable garden. Some also have other garden uses as screens, sun shades, groundcovers and more.
Long term perennial vegetables can be beneficial for the soil as they help build it up through leaf fall and root sloughing, If the soil is undisturbed its natural structure can re-establish itself (of course digging perennial roots will disturb this).
The obvious advantage of perennial crops is that you don’t have to plant seed every year and they don’t have to grow from tiny seeds every year. Because they start out bigger, they can grow a lot faster.
There are some disadvantages to perennial crops and in all honesty I must say they are not nearly as valuable as the fruit trees or shrubs. Annuals can put all of their energy into producing food, whereas perennials have to also put energy into growth and maintenance. Also perennials last for more than one season, thus enabling disease and insect pests to get established and spread. An example of this is the Potato, which is a perennial in mild climates, but prone to disease problems when grown in this way.
One way around the disease problem is to plant / replant, whereby you actually dig up the whole crop and then replant some part of it in a different part of the garden. This is why shallots, garlic and potatoes are normally grown in this way.
Another problem with perennials is that they take up space year round and most aren’t productive enough to justify taking up space in the intensive vegetable garden. Fortunately most are also fairly independent and can be planted anywhere suitable conditions are found. You might also have some special perennial beds close to the vegetable garden. The more rugged plants work well as buffer zones to protect the more delicate annuals from insect pests and wind.
Probably one of the biggest problems of perennial vegetables really has nothing to do with their qualities or cultivation. It is simply that it can be difficult to find material (seed or vegetative) to plant. Some of the rarer crops are almost impossible to obtain.
Gophers can make it hard to grow perennial vegetables. If not protected by wire these rodents will find anything edible if given enough time. In such cases you may want to grow them in beds protected with wire mesh (you could even harvest root crops by simply pulling up the wire).
There are a surprising number of useful perennial vegetables if you start looking. Most aren’t very common, but have been cultivated as crops at one time or another (sometimes frequently).
Where to grow
Where you put them depends upon the kind of plant and how it is harvested.
The root crops must be disturbed to harvest them, so they are often grown in the annual vegetable garden, where they are treated more like annuals. They are dug up every autumn and a portion of them are replanted. Often the larger roots and tubers are eaten, while the rootlets and smaller tubers are replanted to produce a crop next year. In some cases you don’t have to replant part of the crop, enough will remain in the ground to regrow without your help. Such plants tend to be fairly independent and can compete well enough to go in the semi-wild garden, in their own permanent patch.
Some plants just stay in an out of the way place and you harvest their greens or bulbs for a few weeks each year. These are commonly planted in their own bed too. In some cases you might have a special bed for growing a specific perennial vegetable. Plants such as Camas, Lilies and Cannas need to increase to a critical mass of plants before they become very useful for food. Pick too early and you risk wiping them out. Other plants (Chinese Artichoke, Chufa, Oca) are almost weedy in their ability to grow and multiply. These don’t need quite as much care.
Perennializing biennials and annuals
When thinking about perennial food beds don’t overlook the biennials and annuals. With the right techniques some of these self-sow so readily that they can be grown in perennial beds. These include Burdock, Cilantro, Chicory, Parsnip, Carrot, Hamburg Parsley (of course you may still have pest problems when grown in this way).