The answer to 'why is my deck overgrown' is that your deck likely needs regular maintenance and cleaning to prevent the growth of weeds, moss, and other vegetation. Decks are exposed to the elements, and without proper care, they can become overrun with plants that take root in the cracks and crevices of the wood.
Common causes of an overgrown deck include lack of cleaning, inadequate staining or sealing, and poor drainage around the deck. Over time, dirt, leaves, and other debris can accumulate, providing the perfect environment for plants to thrive. Additionally, if your deck is in a shady or damp area, it may be more prone to moss and algae growth.