If you snap a giant horsetail stem, you’ll see that it’s hollow inside.
It is one of about 15-20 species of horsetails worldwide. They like to grow in colonies, when possible, which is why you often notice them growing in dense patches alongside trenches in roads or trails.
If they look prehistoric, it’s because they are. They can be traced to a group of plants dating back 300 million years that once grew as tall as nearly 100 feet.
The stems and what look like stringy needles but are actually thin branches, are tough to the touch. That’s because their cell walls have silicone dioxide in them.
Unlike other plants, horsetail stems — not the leaves — are photosynthetic. The stems of the sterile giant horsetails are evergreen, bluish-green in color and segmented by dark-brown rings, each with whorls of very thin branches sprouting from them.
The fertile stems are thicker, whitish-pink or brown with cone-like spores at their tips that grow only in the spring. The fertile plants have no needle-like growth on them.
The giant horsetail can grow as tall as 10 feet.
Native coastal people used to eat the young spore-bearing shoots of the plant as a springtime vegetable.
Sources: “Plants of the Pacific Northwest,” by Jim Pojar and Andy MacKinnon