ORRIN MORRIS: Nodding thistle a troubling invader

“The prudent see danger and take refuge, but the simple keep going and pay the penalty” (Proverbs 22:3). These are wise observations that may be applied to people regarding the control of thistle, especially today’s wildflower.

NODDING THISTLE

Carduus nutans

Thistles are in the composite family because their blossom head is a mass of slender tubular flowers. As noted in the previous articles, the only way to see the delicate details is to split the head open and view them through a magnifying glass.

Most thistles are spiny with prickly leaves and thorny stems, especially near the bloom heads. Most of the dome-shaped blooms are pinkish-lavender. The stickers around the head discourage ants from getting to the unusually sweet nectar and prevent grazing animals from eating them. However, the thistle we examine here may be beautiful, but it is especially deadly to many animals and is an aggressive invader of pastures and hayfields.

The nodding thistle is a recent resident of the Southern U.S. As late as 1975 it was believed to inhabit areas “north of a line from Maryland to Illinois.” In the South, it was first seen along the roadside sand in vacant fields, but now it has invaded the pastures and hayfields. This rapid proliferation of the species has caused it to be placed on the list of invasive plants. (Klimas and Cunningham)

Close examination of this variety of thistle reveals long stout thorns, especially on the basal leaves. Those thorns are so stout that serious injury occurs to livestock that eat them. Thus, once it has invaded a hayfield, the hay cannot be mowed and baled useless every nodding thistle has been removed. Such removal requires pulling the plant by hand while wearing heavy gloves. Further, every leaf that falls off must be recovered, too. For these reasons, some farmers let their infested field go fallow.

The “colorful” bloom-head forms at the top of a stem that reaches four or more feet high. The bud stands upright but as the blossom opens it tilts, as seen in the sketch. Since this is such a tall specie of thistle the wind easily spreads the seed widely.

Nodding thistles normally bloom from June to October; however, some years I have seen them blooming along the roadside much earlier.

Nectar-gathering butterflies, moths, and carpenter bees seem to be the only beneficiaries of the nodding thistle. This plant is fast becoming a deeply troubling invader and thus a threat to all in the agricultural sector of our economy. Remember, all that seems attractive may indeed be destructive (or sinful?).