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•8 min read

Fall Leaves and Chromatography: The Colors That Were There All Along

The usual explanation for fall color is that leaves change from green to orange. The better explanation, and the one that leads somewhere, is that the orange was in there the whole time and the green was covering it up. You can prove this at a kitchen table in an afternoon with a coffee filter and a bottle of rubbing alcohol.

What Is Actually Happening in the Tree

Leaves are full of pigments. Chlorophyll, which is green, does the work of photosynthesis and is present in overwhelming quantity through the growing season. Carotenoids, which are yellow and orange, are present the whole time as well, but they are simply outnumbered.

As days shorten and temperatures drop, deciduous trees stop maintaining chlorophyll, which breaks down relatively fast. The carotenoids that were always present are left behind, and suddenly visible. Reds are a partial exception: many of those anthocyanins are produced in the leaf during autumn rather than merely revealed.

Pulling the Pigments Apart

Paper chromatography with a green leaf

  1. Tear two or three green leaves into small pieces and put them in a glass jar
  2. Add just enough rubbing alcohol to cover them, then mash with the back of a spoon
  3. Set the jar in a shallow bowl of hot tap water for about thirty minutes, swirling occasionally, until the alcohol turns deep green
  4. Cut a strip of coffee filter, tape the top to a pencil, and rest the pencil across the jar so the strip barely touches the liquid
  5. Wait sixty to ninety minutes without disturbing it, then remove and dry the strip

Different pigments travel up the paper at different speeds, so the single green smear separates into bands. Green stays lower, yellow travels higher. That separation is the whole experiment, and it is the same technique used in real laboratories, just with cheaper paper.

Safety and the Common Failure Points

Before you start

  • Rubbing alcohol is flammable and its vapor is unpleasant, so work in a ventilated room and away from any flame
  • Use hot tap water, never a stove or microwave, to warm the jar
  • Adults handle the alcohol and the hot water; kids do the mashing, taping, and observing
  • If the strip is fully submerged, the pigments wash off instead of climbing, which is the single most common reason this fails

The Comparison That Makes It Science

Running it once produces a pretty strip. Running it three times, with a leaf from three different trees, produces a result. Ask the kid to predict which tree will show the most yellow before any strips are read, then line the finished strips up side by side.

Better yet, save a strip from a still-green September leaf and repeat with a leaf from the same tree in late October. The bands shift, and the kid has physical evidence of a change they were told about but had never seen.

Seasonal Experiments, Already Scheduled

The planner maps experiments across the year so seasonal ones like leaf chromatography land in the week when the materials are actually outside your door.

Launch Science Kit Planner →

Published on September 21, 2026 • 8 min read