The answer to 'why is my stone walkway overgrown' is that your walkway has likely become overgrown with weeds, moss, or other vegetation due to a lack of regular maintenance. Over time, wind, rain, and other environmental factors can carry seeds and spores onto the stones, allowing plants to take root and spread.
Some common causes of an overgrown stone walkway include infrequent weeding, lack of edging or bordering to contain the vegetation, and improper drainage that allows moisture to accumulate. This creates an ideal environment for unwanted plants to thrive.