Gardening glossary
Transpiration
Transpiration is the plant equivalent of sweating. Water absorbed by the roots travels up the xylem (the plant's plumbing), reaches the leaves, and evaporates through microscopic pores called stomata on the underside of the leaf. As water exits the leaf, it pulls more water up behind it — a continuous "transpiration stream" that also delivers dissolved nutrients from soil to growing tips.
Transpiration is climate-driven. Four variables push the rate up or down:
- **Humidity.** Dry air pulls water out faster. A tropical plant in 20% winter humidity can lose water three times faster than the same plant at 60% humidity. - **Temperature.** Warm air holds more moisture and accelerates evaporation. - **Air movement.** A ceiling fan or open window increases transpiration significantly. - **Light.** Stomata open when the plant is photosynthesizing, so daytime transpiration vastly exceeds nighttime.
This is why a plant's watering needs change with the seasons even if you never move it. A pothos that drinks a cup every five days in summer might need the same cup every twelve days in winter.
When transpiration outpaces what the roots can supply, leaves wilt. Brief afternoon wilting in a vegetable garden on a hot day is normal — the plant has closed its stomata as a protective measure. Persistent wilting means either root damage, root rot, or genuine drought.
Crispy brown leaf tips, especially on calatheas, prayer plants, and spider plants, are almost always a transpiration imbalance: the plant transpires faster than it can deliver dissolved minerals to the leaf edge, and the tip dies back. Higher humidity, distilled water, and consistent soil moisture usually fix it.
Grouping plants together creates a small humid microclimate from their combined transpiration — a free humidifier for the rest of your collection.