The Holy Grail of Wild Foods? How to Gather, Prepare, and Enjoy Eating Canada Thistle

Kevin Timoney, Treeline Ecological Research, 21551 Twp Rd 520, Sherwood Park, Alberta T8E 1E3; email: ktimoney@interbaun.com

Introduction
Canada Thistle, Cirsium arvense L., is both misnamed (it is not native to Canada) and under-appreciated. Much has been written about its negative effects. It invades native plant communities and is prickly, competitive, and difficult to eradicate. Sadly, thousands of hectares of landscape in Canada and the United States are subjected to chemical herbicides each year in a futile effort to control this weed. Herbicidal contamination of ecosystems is a serious problem, more serious than the effects of Canada Thistle. But more to the point, can the plant lover and botanist do anything with Canada Thistle other than fret about it? Yes, you can eat it.

As a long-time gatherer of wild foods, I have always been drawn towards Canada Thistle. It often grows luxuriantly. Its leaves can be larger than those of lettuce and of a deeper green. And those abundant spines, so prominent and pungent, have long piqued my curiosity. It’s the spines that provided the first clue as to the palatability of the plant.

If you think about evolutionary strategies and anti-herbivory, you know that each defence has an energetic cost. Plants that have few or no defences must grow fast and complete a life cycle before herbivores find them. Many plants use secondary compounds to discourage herbivory. Physical defenses such as spines on stems and leaves, stinging hairs, and toxic resins also act to discourage herbivores. Each plant species follows a strategy that minimizes energetic costs while maximizing protection. Would a plant with abundant spines need harsh secondary compounds to discourage herbivores? In general, probably not. So, there’s the first question... how does it taste? Unlike many wild plants that must be cooked in two waters to detoxify plant parts or minimize harsh tastes, thistle tastes fine raw. Try it—just strip off the spines and have a taste—it’s mild.

So, if thistle grows luxuriantly, is common, and tastes mild, is there any way it can be gathered, processed, eaten, and enjoyed? Well, yes, of course, you can eat most anything if you spend enough time processing it and don’t have a strong gag reflex. I mean is there a way to use thistle that is efficient, fun, and gives you plentiful, nutritious food? Yes, and you don’t have to worry about snipping off the spines with a scissors. In fact, the spines are easily dealt with. It’s the phloem fibers that require the processing, but I am getting ahead of things.

Gathering and Processing Thistle
If you have to spend a lot of time and effort to gather a small amount of wild food, chances are you won’t make it a habit. The method I have developed is fast and easy. The last batch of thistle, from gathering on the land to closing the lid of the deep freeze took 2 hours to put up 2.9 kg net weight (6.4 lbs) in ten freezer bags. If you compare that to how much money, time, water, and effort it takes to grow an equivalent amount of garden vegetables, thistle compares favorably indeed. How is it done?

First, you need the proper habitat. It is obvious that areas subjected to herbiciding and other chemical treatments are not good habitat for the forager. But there is more to choosing thistles than that. Most thistles have insufficient water and shade to form esculent leaves. The best thistles for eating grow in deep, loamy, meadow soils, typically Humic Gleysols, in partial shade along a forest edge or in a willow savannah (Figure 1). In central Alberta, typical vegetation associates in good thistle foraging habitat are Salix petiolaris, S. discolor, Calamagrostis canadensis, Carex atherodes, and Urtica dioica. Canada thistles that grow in direct sun have small, tough “sun leaves” that are mostly spines (Figure 2). “Shade leaves” are larger, more tender, and have more lamina in relation to leaf margin (Figure 3). You want the biggest, healthiest, deepest green thistles with large leaves.

Bring big bags (backpacks, large plastic bags) and leather or gardening gloves to the thistle patch. It is best to gather the plants before they are in full flower, but it’s not critical as you can break off the flowering tops before the next step. Grasp the plant at its base, then pull upwards towards the plant apex (Figure 4). The leaves will strip off the stem, leaving the stem in the ground and a large wad of leaves in one hand (Figure 5). Place the handful of leaves in your bag and move on to the next stem. Repeat until you have all the leaves that you want. Gather only the leaves. Note: you can also snip the plant at its base, then strip the leaves from apex to plant base. In any case, you need to get the feel of how firmly to grip the stem when stripping the leaves—too firm and you pull the plant out, too weak and your hand slides over the leaves without removing them.

In your kitchen, put on a big pot of water to boil. While the water is heating, fill your kitchen sink with cold water, then rinse and pick through the leaves to remove debris, insects, flower heads, and wilted or yellowed leaves. Once the water is boiling, add as many leaves as will cook evenly without matting (Figure 6). Stir with a stout wooden or metal implement so that the leaves don't mat together. Once the water returns to a boil, keep at a full boil for about five minutes. You do not have to boil in two waters as there are no nasty compounds to worry about.

Remove the boiled leaves with a slotted spoon, strainer, or tongs and immerse them in a sink of fresh cold water (Figure 7). Work the boiled leaves with an implement or your hands until they are cool. Remove the cooled leaves and set aside. Once the water on the stove has returned to a boil, add the next batch of leaves to boil. You can reuse the water about three or four times before changing it.

Once you have boiled, cooled, and drained the leaves, they need to be pureed. This is the key step. The pureeing must be thorough to render the spines, and more importantly, the fibers, edible. The spines disappear quickly, but the phloem fibers (probably chiefly from leaf midveins) can be persistent. Add just enough leaves and water so that the leaves puree without clogging the blender. Puree for about four minutes then inspect it. It should be smooth, creamy, and a deep emerald green (Figure 8). If you can see phloem fibers, continue to puree. Put up the puree in freezer bags or use it fresh.

Eating Thistle
You can use thistle as a soup base, in dips, spreads, or sauces, in bread or omelettes, or thickened with mashed or instant potatoes and eaten as you would cooked greens. The taste is mild and the colour is brilliant. You don’t have to get fancy. Just a little salt and pepper and butter and have at it. However, if you’d like something a little off the beaten track, try--

“Thistle Sopa Gomacho”
Put fresh or thawed pureed thistle leaves into a blender. Add water, some mayonnaise, sun-dried tomatoes, wine, marmite, garlic cloves, tabasco sauce, worcestershire sauce. Puree for about 2-4 minutes. If it does not puree properly, add liquid. You can thicken the soup after the fact by adding mashed potatoes or instant potato flakes. How much you add of each ingredient is a matter of taste. The only important thing is to use enough liquid so that the ingredients blend nicely. You can substitute or add other ingredients, such as milk, cream, butter, buttermilk, olive oil, onion, lemon or lime juice, avocado, anchovies, other vegetables, any spices that you like.

Warm or cold, chemical-free, wild-gathered, nutritious thistle, what could be better?

Figure captions.

Figure 1. The best place to gather thistle is in the partial shade of imperfectly-drained willow savannahs and thicket edges.

Figure 2. Thistles that grow in direct sun have small leaves with little lamina and lots of spines and fibers; avoid gathering these.

Figure 3. Shade leaves grown on soils with no moisture limitation are choice for gathering.

Figure 4. The grip for stripping leaves. Squeeze the stem between the thumb and forefinger and pull.

Figure 5. A handful of stripped leaves.

Figure 6. Boiling the leaves.

Figure 7. Cool the cooked leaves in a bath of cold water.

Figure 8. The finished puree, ready to eat.