P

Parent Branch or Stem – The tree trunk or the larger limb from which lateral branches are growing.

Photosynthesis – The transformation, in the presence of chlorophyll and light, of carbon dioxide (from air) and water (primarily from soil) into a simple carbohydrate and oxygen.

Permanent Branches (Permanent Limbs) – Branches that will remain on the tree for many years, perhaps throughout their lives.

Permanent Wilting Point (PWP) – Amount of water in the soil when a plant wilts and will not recover unless water is added. Contrast with wilting point.

Photosynthesis – The process that converts light energy, carbon dioxide and water into chemical energy and oxygen in green plants.

Phytotoxic – Poisonous to plants

Pollard – Pruning technique by which young trees or branches are initially headed and then re-headed on an annual basis without disturbing the callus knob.

Primary Root Plate –A radial distance from the base of the tree equal to three times the tree diameter (DBH). This represents the critical area where root cutting will compromise the structural stability of the tree. Whenever healthy trees fail due to extreme soil saturation and/or high gusting winds, the root plate is generally visible rootball, where the roots fail.