Alder saplings grow into Alder trees when planted. Alder trees can be harvested for Alder logs and Alder leaves (which yield more Alder saplings). Alder saplings cooked in an oven yield Wood Ash, and have a chance of producing Reek of Misfortune.
Alder saplings can initially be acquired only by using Mutandis
on another planted sapling (does not matter which type). Given the
mutation of the sapling is random, it may take a few goes before Alder saplings appear.