How to Identify Thistles: A Guide for Nature Enthusiasts
How to Identify Thistles?
To identify thistles, you can look for specific characteristics depending on the type of thistle.
Clustered thistle is a native thistle with red-purple flower heads, a cobwebby appearance, and long tapered bracts.
Edible thistle has branched stems, spiny leaves, and cobwebby flower heads that hang on young plants.
Few-leaved thistle has woolly or smooth stems, creamy-white to purple flower heads, and woolly leaves.
Wavy-leaved thistle has white-hairy branched stems, solitary pale lavender to white flower heads, and leaves with shallow wavy lobes.
Non-native invasive thistles include bull thistle, Canada thistle, blessed milkthistle, Italian plumeless thistle, and Scot’s thistle.
Among them, blessed milk thistle is highly invasive with large purple flower heads and distinct white marbled leaves.
Italian plumeless thistle and slenderflower thistle are not known to exist in Clackamas County but have pink-purple flower heads and spiny leaves.
Scot’s thistle, also not known to exist there, has purple flower heads and spiny leaves.
Control measures for thistles involve cutting them off below ground or using herbicides before they grow taller than 6 inches.
Key Points:
- Thistles can be identified by specific characteristics depending on the type
- Clustered thistle has red-purple flower heads, a cobwebby appearance, and long tapered bracts
- Edible thistle has branched stems, spiny leaves, and cobwebby flower heads
- Few-leaved thistle has woolly or smooth stems, creamy-white to purple flower heads, and woolly leaves
- Wavy-leaved thistle has white-hairy branched stems, solitary pale lavender to white flower heads, and leaves with shallow wavy lobes
- Non-native invasive thistles include bull thistle, Canada thistle, blessed milkthistle, Italian plumeless thistle, and Scot’s thistle
- Control measures for thistles involve cutting them off below ground or using herbicides before they grow taller than 6 inches
Did You Know?
1. Thistles belong to the aster family and are easily recognized by their prickly leaves and vibrant purple flowers.
2. The ancient Greeks believed thistles to have therapeutic properties and used them for various medicinal purposes, such as treating sore throats and digestive issues.
3. Thistles are often associated with Scotland and are considered a national emblem. The Scottish thistle, also known as Onopordum acanthium, holds significant historical and cultural value for the country.
4. Some thistle species have edible parts, including their young shoots, leaves, and roots. These parts can be incorporated into recipes and eaten raw, steamed, or even pickled.
5. Due to their ability to spread quickly and dominate areas, some thistle species are considered invasive plants, posing a threat to native flora and agriculture.
Frequently Asked Questions
How do you identify thistles by leaves?
Thistles can be identified by their distinctive leaves. Look for leaves with elongated, lanceolate segments that taper to a point and are adorned with long, needle-like spines. Additionally, the stems of thistles are lightly hairy and feature spiny wings, particularly in the upper section of the plant. Another key characteristic to note is the spreading, long, spiny phyllaries. When it comes to the flowerheads, they are typically large and display a reddish-purple hue, with one to three flowerheads per stem.
How do you differentiate thistles?
To differentiate thistles, observe the presence of spiny wings along the stem length. If the stem is lined with prominent spiny wings, it is likely an exotic thistle. However, if there are only a few spines or spiny wings intermittently along the stem, it could be either native or exotic. Additionally, a helpful way to distinguish thistles is to examine the bracts on the flowering head and compare them to known native and exotic thistle species.
What is the appearance of thistle?
Thistles are characterized by their unique and striking appearance. They have lobed, spiny leaves and stems that are often covered in thorny spines. These herbaceous plants belong to the aster family and produce composite flowers, with each flowerhead containing numerous tiny florets. The vibrant flowers of thistles come in shades of purple to pink and vary in size, ranging from small half-inch flowers to larger three-inch blossoms.
What are the characteristics of thistle plants?
Thistle plants are easily recognized by their oblong to lance-shaped leaves, measuring between 2 to 8 inches in length. These leaves are prickly in nature and are arranged alternately along the stem. In some cases, the leaf bases extend downward as prickly wings, approximately 1/2 of an inch long. The leaf edges of thistle plants vary from being almost smooth to possessing shallow lobes and toothed margins.