There are several plants in the Sonchus genus that have become naturalized all over the world. Sonchus oleraceus, common sow thistle, is similar to other Sonchus and it’s difficult to tell the difference. The ones most similar, S. asper and S. arvensis, are also called sow thistle and can be used in the same way as S. oleraceus. Texas A&M University, foragefax.tamu.edu , in their article “Weed of the Week: Spiny Sow Thistle (Annual)” said, “Many growers make no distinction at all between perennial and annual sow thistles. That’s because all three versions are tall weeds with yellow, dandelion-like flowers and stems that produce a milky sap, latex. Seedlings of the two species (Sonchus asper & Sonchus oleraceus) are practically indistinguishable and may be difficult to tell apart ... without examining the root system.”
Sow thistles are not true thistles, though there is a resemblance. They are in the Asteraceae, daisy family. And, just like the dandelion’s seedhead is fluffy and blows away in the wind, so does sow thistle’s. Dandelion sends up one stem with one flower on top. Sow thistle, a much larger plant, branches as it gets older sending up multiple stems, which have multiple flowers. On the same plant you may see flower buds, flowers and fluffy seedheads, pappus, at the same time. The plant can reach 3 feet. It starts out as a rosette of leaves laying on the grass. The alternate leaves can have varying shapes on the same plant and may have reddish-purple streaks. They may have spikes that look sharp, but when you touch them, they feel like the rest of the leaf, which can be more than a foot long and almost 5-inches wide. As the plant gets older, the spikes stiffen to varying degrees. Leaves near the top of the stem clasp it.
The stem has ridges and may have reddish-purple streaks. If you cut it, you’ll see the latex and that the stem is hollow. The flowers are about an inch across. Each plant can produce up to 8,000 seeds that are carried by the wind on pappus. Each seed can remain viable in the ground 8 months or more if they remain in the top ¾ inch of soil. Seeds buried deeper can remain viable for up to 30 months. Seed information is from the Global Invasive Species Database, iucngisd.org, in their download “Full Account for: Sonchus oleraceus”.
Sonchus means “hollow” and oleraceus means “edible” or “cultivated.” Often plants with white sap are not edible, but for sow thistle the entire plant is edible and nutritious containing carbohydrates, proteins, vitamins and minerals. There are many recipes online.
Some say the roots can be used as a coffee substitute, but I would say coffee extender. I experimented with an older plant, about 2-feet tall. I cut up and baked a fresh root in my toaster oven at 200º F until it was dry and brown, about two hours. I ground it to powder in a spice grinder and it resembled instant coffee. Adding it to hot water made an interesting herbal drink, but it didn’t taste like coffee to me. However, when I mixed it with coffee, all I could taste was the coffee. That’s why I call it an extender. I didn’t experiment very much with the roots, so your mileage may vary.
I put the flower buds in pickle juice. After a day or two you can use them the way you use capers. Be sure to pick the buds while they’re still rounded at the ends, before they push out. If you wait too late, in my opinion, they’re too fibrous to eat raw. If you pick the leaves when they’re young, you can use them raw in a salad. Older leaves go into the cook pot. The stalk is edible peeled and cooked. I treat the flowers like dandelion flowers: pull them apart and sprinkle yellow bits raw on salads.
Rabbits, pigs and other animals eat Sonchus. This accounts for the common name sow thistle. Bees, flies and other pollinators enjoy it, but, it can be invasive, causing problems for farmers and gardeners.
Traditional medicine systems use Sonchus to treat the liver, warts, women’s issues, etc. The National Institutes of Health, ncbi.nlm.nih.gov, has several articles describing its antioxidant properties. Some people are allergic to the plant. Several species of Sonchus are in the Food and Drug Administration Poisonous Plant Database at fda.gov.
Sow thistle is not esthetically pleasing to many people, so it’s rarely left to grow above mower height. But if you let it grow, you may see it covered with aphids. You may also notice that the aphids are not on your other plants. This is what the article “Sonchus” at en.wikipedia.org said about that, “Sow thistles are common host plants for aphids. Gardeners may consider this a benefit or a curse; aphids may spread from sow thistle to other plants, but alternatively the sow thistle can encourage the growth of beneficial predators such as hoverflies. In this regard, sow thistles make excellent sacrificial plants.”
Deborah Richardson is a freelance reporter for The Examiner with a fondness for flora in its natural setting.