On the 27th day of the experiment, the researchers measured stem length, root-system length and the overall weight of the plants.

It spreads primarily by underground stems; colonies form when pieces of the root system or whole plants float into an area and take root or when seeds float into a suitable area and germinate.

A group of thousands of aspens can actually constitute a single organism, called a clone, that shares an interconnected root system and a unique set of genes.