Thistles are the bane of picnickers, campers and hikers. Who hasn’t stepped on or brushed against the sharp, unforgiving spines of a thistle? For many people, interactions with thistles have generally been painful and irritable.
However, there is another side to this story. Thistles provide important habitat and food sources for native fauna. The nectar and pollen from the flower heads are valuable food sources for bees, butterflies and other pollinators. The seeds are an important food source for seed-eating birds. Many insects feed on the leaves, stems, and flowers of the thistles. In addition, thistles are edible.
In Florida, there are seven species of true thistles (genus Cirsium), which belong to the Aster family (Asteraceae). However, in Southwest Florida, only two species are found: the Nuttall’s thistle (Cirsium nuttallii) and the more common purple thistle (Cirsium horridulum). Purple thistles are commonly found in pinelands, prairies, roadsides and disturbed sites.
As with most thistles, the purple thistle is a biennial — that is, a plant that lives for two years. It usually forms a basal rosette of leaves in the first year, then flowers and fruits the second year. In southern Florida, the seasons can be mixed, with the plant not taking a break between first and second year growth.
Typically, the purple thistle goes through three stages of growth. The first stage, or rosette stage, takes place during the winter months. During this stage, the plant consists of a rosette of leaves that are circular and growing flat or close to the ground. The second stage, or bolting stage, takes place from late January through July. The stalk of the thistle bolts up from the rosette. The third stage, or flowering stage, takes place from April through August. This is when the plant reaches maturity, producing flowers and then seeds.
A mature purple thistle can reach a height of 2 to 5 feet. The lance-shaped grayish-green basal and stem leaves can be up to 10 inches long and 2 inches wide, with the longest leaves near the bottom of the stalk. The leaves are deeply lobed and the leaf margins are toothed. Each tooth is armed with a sharp spine. It’s no wonder this species is named horridulum.
One or more flower heads form at the top of the stalk. The unopened flower buds resemble tiny artichokes. However, when open, the bloom looks like a purple shaving brush contained within a fortress of small spiny leaves.
Actually, the flower head is composed of a receptacle with many small flowers (florets) surrounded by a whorl of spiny bracts (leaf-like structures). The color of the blooms can vary from rosy purple to lavender to pink. Yellow and white blooms are also known not very common. These blooms can be up to 3 inches wide.
Once the plant flowers, it can produce up to 4,000 seeds. The tiny seeds, each equipped with a small spine, are attached to silky white threads designed to catch the wind. The once-purple blooms now look like balls of white fluff.
The purple thistle provides a very attractive food source for bees, butterflies, and other insects. It also functions as a larval host plant for the little metalmark and painted lady butterflies.
Believe it or not, purple thistles are edible. The stalks, leaves trimmed of their spines and roots are edible. They can be eaten raw, steamed or boiled. A tea can be made from their leaves. More information on gathering and preparing this plant for eating can be found at http://bit.ly/2uXFVjS.
Purple thistles are now in bloom. Enjoy their beauty, but be careful around them.