BRR • WONDER 029 • BRR-DP-2026-09-09 • OUTDOOR • SEPTEMBER 9, 2026
TODAY’S WONDER
Why do leaves change color?
Most of the colors were there all along. Autumn just makes the green step out of the way.
TOPICS: Plant Biology • Seasonal Change • Pigments • Observation • Prediction
TODAY’S INVESTIGATION • THE LEAF COLOR SHIFT LAB
A small outdoor seasonal-change investigation using naturally fallen leaves as a living dataset. Collect a handful, arrange them from “most green” to “least green,” inspect where the color is changing, and make one prediction worth checking again later.
Best suited for: ages 3+ with close adult supervision • 15–25 minutes • Outdoor
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TRY IT TODAY
Find 4–8 naturally fallen leaves showing as much variation as you can find: dark green, pale green, yellowing, brown-edged, spotted, fully changed, or gloriously indecisive.
- Arrange the leaves from most green → least green.
- Look closely: is the color changing at the edges, around the veins, in spots, or unevenly across the leaf?
- Choose one Specimen of Questionable Behavior and make a rubbing or sketch.
- Look at nearby trees or shrubs. Are they all changing at the same rate?
- Make one prediction: “When we come back in about a week, I think ______ will be different.”
- Photograph or record the lineup so the same spot can be checked again later.
If everything is still green, excellent. Record: NO COLOR SHIFT DETECTED. REPEAT TESTING INDICATED. A baseline before the obvious change is still a result.
WHAT’S HAPPENING?
During spring and summer, chlorophyll is abundant and usually dominates what we see, making leaves appear green while supporting photosynthesis. As autumn brings shorter days and cooler temperatures, many deciduous plants reduce chlorophyll production. As that green pigment fades, other pigments become easier to see. Carotenoids contribute yellow, gold, and orange tones, while anthocyanins can contribute red and purple. Species, light, moisture, elevation, and temperature all influence the timing and intensity of the display.
SAFETY + CLEANUP
Use naturally fallen leaves rather than pulling vegetation. Skip plants you cannot safely identify, moldy or heavily decayed material, poison ivy or other irritating species, and unsafe roadside or steep areas. Nothing goes in mouths. Wash hands afterward. Return unneeded specimens outdoors, shake approximately half the ecosystem off everybody’s clothes, and accept that one leaf will probably appear in the house three days later.
REFERENCES • GO DOWN THE RABBIT HOLE
U.S. National Park Service — Rocky Mountain National Park: Learn About Fall Colors • verified September 9, 2026
Revision: v1.0 • September 9, 2026 • Initial paired Wonder Jar release.
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