Handbook of Nature-Study · Lesson CXL · Topic 22: Weeds and wayside plants
140. The common, or lance-leaved, thistle
Goal: Your child explains how the thistle's spines protect it, studies its flower-head as a family, and looks closely at a thistle balloon.
You'll need
- Nature notebook, pencil and colored pencils
- A hand lens (magnifying glass)
- Garden gloves
- A paper bag for a few seed-heads
What's in the book
A Teacher's Story about thistles, with a drawing of the Canada thistle, and the lesson: Leading thought, Method and nine questions.
The lesson, step by step
When and where
Thistles bloom from about July to September in pastures, roadsides and fence corners. The fluffy seed-heads follow in late summer and fall. Wear gloves to handle them.
The leading thought
The thistle is covered with sharp spines, and these serve to protect it from grazing animals. It has beautiful purple flowers, arranged in heads similar to those of the sunflower.
Where and how many
Where do you find the thistles growing? Do you find more than one species growing thickly together?
Armor
Do the spines grow around the margins, or on the leaves and veins? Are the leaf edges flat, or wavy and ruffled?
Look without touching. Say: Which way do the spines point? What would happen to a cow's nose?
Flower-heads and visitors
Which blossom-heads open first—the topmost or those lowest on the stalk? Are the flowers fragrant? What insects do you most often see visiting thistle blossoms for pollen or nectar?
Use the Lesson CXXXV outline on one head. Thistle heads have only disk-flowers, no banners.
The balloon
Carefully study a thistle balloon. How is the floss attached to the seed?
How far do you think the thistle balloons might travel?
With gloves, pull one seed from a ripe head and look at the down with the lens. Then let it go outdoors (not in a garden!) and watch it float.
Nature notebook
Draw a spiny leaf and a thistle balloon with its seed hanging below. Wash hands when you come in.
Afterwards
Look for a flat thistle rosette in fall. Comstock asks what it does the second summer.
Answers to the book's problems
The Canada thistle cannot be cultivated out like the others because it spreads by creeping underground rootstocks; cutting it up just makes more plants. (Comstock's weed essay calls it a perennial.)
Worked out for this site from the scan. If a number in your copy differs, trust the book.