Look closerFungi
Why lichen turns bright green after rain
When: All year
Rain turns a lichen's gray outer fungal layer transparent, letting the algal partner inside show bright green, while lichens with cyanobacteria shift toward dark green, brown, or black.
Why this time of year
This one works in any month with rain, and New England shade-tree bark and stone walls carry lichen within a short walk of most Sudbury doors.
How to notice it
- Before rain, find a dry lichen patch on bark, a boulder, or a stone wall and note its exact color.
- Return to the same patch during or right after rain and compare.
- Look for the switch: gray-green turning bright green, or pale patches turning dark.
- Use a magnifier if you have one; touch gently and never peel.
Try this with kids: Can you find the same patch before and after it dries?
a lichen is a fungus living together with algae or cyanobacteria that make food from light
Safety
- Look and touch lightly; do not peel lichens from bark or stone.
Sources
- fs.usda.govA dry lichen is usually gray or colored like the fungal cells of its upper cortex; when wet those cells become transparent and the algal cells beneath show through, bright green for green algae and darker tones for cyanobacteria