Frost Flowers

Not Really Flowers


Photo of frost flower, ribbonlike frozen sap at base of plant stem
"Frost flowers" are ribbons of frozen sap that form at the bases of certain plants during the first hard freezes in fall.

If you’ve been out exploring the countryside on a cold, late-autumn morning, you may have encountered the short-lived frost flower. Not really a flower at all, frost flowers are delicate, beautiful ribbons of ice crystals that form on the lower stems of a few species of Missouri native plants.

They usually only appear in late fall

Frost flowers typically occur only in late fall after the first few hard freezes and while the ground is still warm. Their season is brief, and they disappear quickly on the day they occur, melting like frost when the air warms or rays of sunlight fall on the delicate structures.

How they form

While the plants’ stems are ruptured by the first hard freeze, the root system is still sending up plant sap from the warmer ground. The sap pushes through the broken stem and freezes on contact with the cold air. As more saps moves up, it forces the freezing stream of white ice crystals into ornate, folded ribbons that look like petals, puffs of cotton candy, or snarls of white thread.

Missouri plants that produce them

Missouri plants known to produce frost flowers include dittany (Cunila origanoides), stinkweed (Pluchea camphorata, which is not widespread in Missouri), and white crownbeard (Verbesina virginica). Scientists don’t know what it is about these species that allow them to produce frost flowers. Perhaps their root systems are more active later in the year than other species, or their stems rupture in just the right way to force the ribbons of sap. Whatever the reason, frost flowers only appear on the stems of a few species.

Get outside early on late fall mornings

Even experienced nature explorers have never seen frost flowers. This is because you have to be in the right place at the right time. Get to know Missouri’s frost-flower plants and find places where they grow naturally. Then keep your eye on the calendar and the weather. When it starts to frost in the fall, plan to get out early and visit the places where you’ve seen frost-flower plants growing. Don’t forget your camera. If you’re lucky, you may snap a few pictures before the ice ribbons melt in the morning sunlight.

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Dittany is a low, much-branched, wiry, shrublike perennial with square stems and aromatic leaves. Flowers are small, in tufts arising from leaf axils, and purple to lavender, each flower with a tiny, 2-lobed upper and a broader 3-lobed lower lip. Blooms July–November. Leaves opposite, sessile, almost triangular with a broad base and a lancelike point, finely toothed. The green parts have a delightful fragrance.

White Crownbeard

White crownbeard is a tall perennial with winged stalks. The wings are extension of leaf tissue. The flowerheads are small, clustered terminally, 1–1½ inches across with few (1–5) ray florets, and white. Blooms August–October. The leaves are alternate, oval to lance-shaped, to 7 inches long, with short fine hairs above and hairier below, also with widely spaced, small teeth.

Yellow Crownbeard

Yellow crownbeard is a tall perennial with hairy, winged stems. Flowerheads are few (1–10 per stem), yellow, with 8–15 rays spreading horizontally and varying in length. Blooms May–October. The leaves are coarsely hairy on the upper surface, ovate-lanceolate, 2½–6 inches long, alternate, with widely spaced, small teeth.