Bull Thistle and Whorled Milkweed in Winter

by Carl Strang

Today’s winter botany focus is on one plant that is very conspicuous and another that is much less so. The conspicuous one is the bull thistle.

The dense, spiny leaves all remain attached, intimidating in winter as in summer.

The dense, spiny leaves all remain attached, intimidating in winter as in summer.

The heads bend to become oriented in various directions.

This is a weed with visual interest, but not what I would call cuddly.

This is a weed with visual interest, but not what I would call cuddly.

Some insects, however, find this plant very approachable when it is blooming.

A tiger swallowtail fills its tank at a bull thistle flower head.

A tiger swallowtail fills its tank at a bull thistle flower head.

For contrast, let’s look at what becomes of whorled milkweed.

Not a very tall plant, whorled milkweed’s narrow leaves further diminish its visual impact even when it is green. Only the flowers grab the eye.

Not a very tall plant, whorled milkweed’s narrow leaves further diminish its visual impact even when it is green. Only the flowers grab the eye.

In winter the leaves fall away.

The foot-tall stems may remain upright or tilted.

The foot-tall stems may remain upright or tilted.

Some of the opened seed pods may remain attached.

The pod’s shape and mottled color pattern on the relatively diminutive stem help with identification.

The pod’s shape and mottled color pattern on the relatively diminutive stem help with identification.

Fortunately this is a plant that tends to grow in colonies, so even if some individuals have lost all their pods and seeds, a few should remain.

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