Reindeer Moss, also known as caribou moss, is not moss
It is a lichen. This means that it's two different life forms at once. It is an alga living side by side and working together with fungi. That said, it is understandable how the mistake can be made. Reindeer moss looks very similar to a wet bush of thistle-like branches. These branches are a pale greenish grey, making it even harder to distinguish this lichen from real plants. Because reindeer moss is a lichen, they do not flower. Instead, the fungi part of the lichen creates small disc-like growths that allow fellow lichen to mate with each other. Lichen also doesn't burrow roots into the ground. They grow on the surface of the ground, and on the surface of rocks.
Reindeer Moss grows in the Canadian Tundra
Even though the "moss" part of the name "reindeer moss" is false, the "reindeer" part of the name is entirely accurate. Reindeer moss is extremely cold resistant and often grows in the Canadian tundra. Thus reindeer usually eat reindeer moss when all other food sources have been wiped out by the cold. Reindeer moss tends to grow best in climates that are cool and moist. Most of their growth takes place during the fall and spring. When their environment is too cold or dark, lichen will enter a dormant state until conditions improve.
Reindeer Moss grows very slow
Although this moss is incredibly durable, has a very long lifespan, and requires next to no maintenance, they are not very good garden items. Reindeer moss grows very slowly. This makes it very hard to grow reindeer moss intentionally. If reindeer moss happens to be growing in your garden, then there's nothing to worry about, as they will not harm or interfere with garden plants. But it is not recommended to seek out reindeer moss for your garden.