How does season affect plant bleeding intensity?

The intensity of bleeding in plants—that is, the rate and amount of sap exudation after a cut—varies greatly with the season, mainly because of changes in root pressure, temperature, water availability, and plant metabolic activity. Bleeding is most vigorous in spring and least noticeable in summer or winter, depending on the species and climate.

1. Spring: Maximum Bleeding

• During early spring, root pressure is at its peak, created by high soil moisture, active root metabolism, and low transpiration.
• Warmer soil temperatures stimulate root respiration and active ion uptake, leading to osmotic water intake into the xylem.
• As a result, hydrostatic pressure builds up, forcing sap upward through xylem when a stem is cut.
• Example: Maple trees and grapevines bleed heavily in early spring, even before leaf growth begins.

2. Summer: Moderate to Low Bleeding

• In summer, high transpiration dominates water movement, drawing sap upward mainly by transpiration pull rather than root pressure.
• Root pressure falls because soil water may be low and plant stomata remain open.
• As a result, when plant stems are cut, very little sap exudation occurs.

3. Autumn: Declining Bleeding

• As temperatures drop and metabolic activity decreases, root absorption slows, and osmotic ion pumping into the xylem is reduced.
• Tree bleeding declines and eventually stops when plant enters dormancy or pre-winter rest.

4. Winter: No Bleeding

• In most temperate plants, bleeding ceases completely during winter.
• Roots become physiologically inactive due to low temperature and frozen soil, preventing root pressure buildup.
• Any cuts or injuries during this period produce little or no sap flow.