The vegetation red edge (VRE) - a sharp increase in reflectance between approximately 700 and 750 nm arising from chlorophyll absorption of visible light and strong near-infrared scattering within leaf tissues - represents the most extensively studied surface biosignature for remote detection of photosynthetic life. This mini-review synthesizes current knowledge of terrestrial vegetation spectral signatures and their relevance to exoplanet biosignature searches. Earthshine and spacecraft observations have quantified the disk-integrated VRE as a few-percent feature whose strength varies with phase angle, cloud cover, and vegetated land fraction, requiring photometric accuracy of ~1% or better for reliable detection. Temporal variability linked to seasonal growth and senescence provides a critical discriminant against abiotic mineral edges. Complementary biosignatures, including circular spectropolarimetry rooted in molecular homochirality and photosynthetic fluorescence, offer independent confirmation pathways that reduce false-positive risk. Detectability on exoplanets depends on host-star spectral energy distribution, cloud fraction, surface coverage, and evolutionary stage of any biosphere; models indicate that VRE-like features could be recoverable on nearby rocky worlds with exposure times of tens to hundreds of hours under favorable conditions. Extrapolation to extraterrestrial environments is further informed by aquatic floating vegetation, extreme-environment analogues, and considerations of prebiotic chemistry. Collectively, these findings underscore that robust life detection will require multi-wavelength, time-resolved, and multi-technique observations rather than reliance on any single spectral feature.
