How do horsetails, ferns, and moulders contribute to the formation of coal?

Coal began to form from tree ferns, horsetails, and composts as early as 400 million years ago. For this process to take place, you need a lot of organic matter and the absence of oxygen, then the decomposition of plants by bacteria is slower and peat is formed. The next layers of plant mass, as it were, squeeze the layers together and the carbon content increases. This is how brown coal is first formed from peat, and from brown coal. The ideal conditions for the formation of coal deposits are a swamp.