What has happened when the perennial has not come back the following year?

When a perennial does not return the following year, it may indicate that the plant has died, possibly due to unfavorable growing conditions, such as extreme weather, poor soil drainage, or insufficient care. Alternatively, it could be a sign of disease or pest infestation that weakened the plant. In some cases, perennials may also go dormant for an extended period and might return later, depending on the specific species and local climate conditions. Regular maintenance and monitoring can help prevent such issues in the future.