Rhubarb, asparagus.... can you think of any other perennial vegetables? Odds are good your answer is no, at least unless you live in a tropical area.
I have been slowly adding edibles to my yard- not just in my annual vegetable garden, but everywhere. It was actually pretty serendipitous that I learned about permaculture when I did, because I have never liked the idea of spending a lot of money or time or sweat on ornamental plants. Permaculture taught me that a beautiful garden can be planted that is ALSO useful, whether it provides food, medicine, animal fodder, or mulch. This finally gave me the motivation to work on areas of my yard other than the large annual vegetable garden. Even with my annuals, I plan on using permaculture practices- because squash bugs have become a problem for me I plan to plant all of my zucchini and squash (all of my curcurbits other than the cucumbers) in random places around the yard, far from my garden.
Back to perennial vegetables- what else can you grow? I've developed a short list of plants that can survive this far North, and hopefully I'll be able to add to this list in the coming years.
- French Sorrel- this is a popular salad green in Europe, and I've actually been growing this one for the past two years. It comes back quickly any time it gets defoliated (by the chickens) or frozen, and it has a pleasant flavor. I'm going to plant a bunch more this year. Buy it here, or keep an eye out for it, it's sometimes available in the herb section at larger nurseries.
- Tiger Lilies- yep, I just said tiger lilies. Actually, several species of lilies are edible, with the flowers and the bulbs being the primary parts eaten. I have a big patch of tiger lilies in my yard, and I know they can reproduce pretty prolifically here, but I haven't tried eating them. I highly recommend you research and make sure the plant/plant part that you eat is, indeed, edible.
- Jeruselem Artichokes/Sunchokes- These sunflower relatives spread via rhizomes, so care needs to be taken that they don't take over your garden (or plant them elsewhere). The roots are the part generally eaten and are a cross between a potato and a radish, and can be used like potatoes in most recipes. I've eaten but not grown these. Buy them here.
- Sea Kale- this perennial kale can be used just like annual kale or collards. According to this entry from Morgan Botanicals on Local Harvest: "The main crop of sea kale is in the spring shoots. The blanched asparagus-like shoots are cut at 6-9 inches and have a slight hazelnut flavor. The flowerbuds, resembling broccoli heads, are not only beautiful and fragrant but also have very good flavor. The leaves of first and second year plants can also be eaten, and taste like collards. In the fall, after flowering is complete, the leaves of more mature plants can be eaten. Roots can be used raw or cooked, usually boiled or steamed like asparagus and served with butter." I have neither eaten nor grown this, but I plan to. Buy seeds either from Restoration Seeds or Bountiful Gardens.
- Chicory- Another green, this one was more difficult to find info on. Some sources list it as a perennial, some don't. And there was little information on it's long term habits. It has a long taproot, often used for medicine and for a tea/coffee replacement, and my guess would be that if cut off at the ground it will sprout new leaves every year (and perhaps this is why it is also called Italian Dandelion). Buy it here.
- Perennial and Clumping onions- Both clumping onions and garlic are "sorta" perennials, and both are widely available (scallions are clumping onions and easily found at most garden centers). You have to pick them and then replant a few of the bulbs, but it still saves you from buying seed every year, and since you plant in the fall it's one less thing that has to be done in the busy(er) spring. But there are truly perennial onions as well- Egyptian walking onions. The onion forms on the top of the stalk instead of underground. Eventually the onion weighs down the stalk and drops to the ground, essentially planting itself. So they walk across your garden. Buy it here (as I plan to!).
- Wild Leeks or Ramps- Wild leeks not only do well in cold weather- they also thrive in full shade, so they are an idea edible to plant in those shady places where nothing but hostas (boo, hostas) will grow. However, they haven't been widely commercialized, so it's not easy to find them. I did find one place, however, to buy them, here.
- Pea Shrub- Yep, beans on a bush. A perennial bush. That's good all the way down to zone 2. Why do more people not grow this? I don't know, but I plan to find out! It's also one of only a few shrubs that fixes nitrogen, which makes it useful in permaculture since every plant should serve multiple functions. Buy it above (the link next to Wild Leeks).
- Ground Nut- and here's a vine that also fixes nitrogen. I'll be trying this one soon as well. It's a climbing, suckering vine that produces edible nut-like roots and that was well known to native Americans. Buy above as well.
Coming soon- fruits you should grow that you've probably never heard of.