If your shrubs and trees are developing splendidly in the garden, cambium has done a good job. This background article will familiarize you with the most important functions of cambium for the growth and pruning care of your ornamental and fruit trees.
What is cambium and what functions does it have?
Cambium is a dividing tissue between bast and wood that is responsible for thickness growth and wound healing in shrubs and trees. It forms new wood and bast by shedding cells inside and out, and creates wound tissue after injury to protect open wounds.
Responsible for thickness growth and wound healing
Botanists define cambium as a dividing tissue consisting of embryonic cells. Behind the scientific, sober definition lies one of the control centers for the growth of shrubs and trees. As the figure below shows, the cambium is located just below the bark between the bast and the wood. The cambium ring fulfills these tasks:
- Intense cell division in two directions during the growing season
- Formation of new wood on the inside and fresh raffia on the outside
- Production of wound tissue after injuries to trunk or branches
The cambium ring is the only layer in the trunk and branch that forms new tissue. The sapwood with elongated vessels develops from the cells released inwards. Water and nutrients are transported from the roots to the leaves through these pathways. Over time, tannins are deposited so that sapwood hardens into heartwood and takes on scaffolding functions. Valuable bast, which also has conductive pathways, develops from the cells released to the outside. Here reserve substances flow from the leaves into the roots. The outer, old bast layer turns into the visible bark.
Cambium turns into callus on cuts
As another key function in the growth of woody plants, cambium heals small and large injuries, such as after pruning or storm damage. The process can be recognized by bulging tissue that forms along the edges of the wound. A special wound tissue, called callus, gradually develops from the exposed cambium. Over time, the newly formed callus tissue covers the open wound to protect it from pathogens and weather influences.
New tissue forms exclusively in the cambium. The thin layer between bast and wood is responsible for the thickness growth in a tree.
Tip
The smoother the edges of the wound, the better the healing process will be after a pruning. To allow cambium tissue to transform into callus and overflow the open wound, cuts are smoothed with a sharp, disinfected knife. After winter pruning, apply a thin coat of tree wax to the edges of the wound to protect the cambium ring from frost damage. Wound treatment is unnecessary the rest of the year.
