The answer to 'why is my deck weeds' is that weeds can often grow between the boards of a wooden deck, especially if the deck is older or not well-maintained. Weeds thrive in the moist, shaded environment under and around a deck, and their roots can work their way into the cracks and crevices. This can make the deck look unsightly and can also cause damage over time.
Some common causes of weeds on a deck include poor drainage, lack of regular cleaning and maintenance, and the use of pressure-treated lumber that may not be as resistant to weed growth as other materials. Symptoms can include visible weeds poking through the deck boards, as well as a general unkempt appearance.