Giant reed naturally thrives across the temperate and tropical regions of Asia, stretching from the Mediterranean basin to East Asia. It has been introduced to and is cultivated in both hemispheres, especially in subtropical and temperate zones, indicating its adaptability and potential utility in various ecosystems. In some introduced regions across the Americas, Africa, and Oceania, giant reed is sometimes thought to be potentially disruptive, impacting local ecosystems. Nevertheless, giant reed's cultivation is practiced due to its attributes, with a mindful approach to its tendency to spread in certain areas.

Giant reed is not poisonous to humans, but may cause allergies from pollen or contact. Common symptoms include allergic conjunctivitis, face flushing, and wheezing. General pollen allergies can cause sneezing, itchy/runny nose, eyes, coughing, difficulty breathing, chest tightness, congestion, and fatigue. Dermatitis can develop after touching giant reed.

Giant reed is a weed that grows widely in North America, Southern Europe, Africa, the Middle East, Oceania, and South America. Its habitats include marshlands and riverbanks. It appears on invasive species lists in most eastern and southern states from Georgia to Pennsylvania, and invasive species laws in Wisconsin and western states from Texas to California. Outside of the US, giant reed is also invasive in parts of South Africa and Australia. The plant forms dense stands and outcompetes native plants for water and soil nutrients. It is highly flammable when dry and can pose a serious fire danger. Hand cutting can be used to target individual plants, or the application of herbicide.

The best season to remove or restrict giant reed is in late winter or early spring, before the plant starts its rapid growth phase and goes to seed. It's important to control or remove it before it can spread its seeds and produce new plants.