The Q&A Archives: Weedy Vine with Spiny Green Fruit

Question: There's an invasive volunteer vine in my yard. It grows from a single 1/2-inch-diameter stem and produces lemon-size spiny green fruit. The bottom of the fruit opens by peeling back to reveal 4 chambers, each containing 1 or 2 large, green to black seeds the size of small olives. Sometimes the seeds have a white covering which dries and falls off. What is this plant, and will it harm the shrubs on which it is growing?

Answer: What you're describing sounds like Western wildcucumber (Marah oreganus), a perennial regenerating from an enormous taproot. The stem is long, thick, angled, and trailing or climbing. Leaves are stalked, blades lobed, roughened, and sometimes reaching 6 inches or more in length and width. Flowers are waxy-white and somewhat star-shaped. The fruit is gourd-like, several inches long, fleshy and spiny. Wildcucumber is native to the western U.S. and Canada, and is also known as bigroot, manroot, old-man-in-the-ground, and Echinocystis oregana. It's harmless to your plants, but it's not the kind of invasive plant you'll want to allow to grow in your yard. Trace the vines back to the root and dig it out -- while you still can!

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