WHY ARE MOSSES SMALL?

Living the little life

Although they have stems and leaves like many other plants (though sometimes moss leaves are microscopic), mosses do not have roots. Roots are a very efficient way of getting nutrients, and mosses get most of their nutrients from the atmosphere through their leaves. This is one of the reasons why mosses are small--they do not have the nutrient capacity to get bigger without roots. 

However, living the small life has its advantages. Because they do not need roots to get nutrients, mosses are not obligated to grow in soil. Because they are so small, they are mostly unaffected by gravity.  These two factors allow moss to grow in areas that other plants cannot grow in, such as small fissures in bark, bare rock, and vertical cliff faces and so they avoid competition for resources with other plants.