B for Bacteria is all around us

Bacteria are microscopic single-celled organisms, and when it comes to trees and ecology they can be good and bad just the same as the ones which affect us as humans. And the bacteria doesn’t need to be on the trees such as bacterial canker often found on the prunus species, it can be in the soil or elsewhere. Bacteria in the soil are plentiful around 100 million to 1 billion in a teaspoons worth! Most bacteria in soil are good an are the decomposers of the plant world. Some even decompose pollutants too, but there are also other types including mutualists, these work with the plants doing good such as nitrogen fixing, particularly working well with Alder and Locust trees. Bacteria are so plentiful they probably merit their own blog or two!


Bark can be attractive, or not, bark can be a great way of determining the health of a tree and damage to bark can be a major problem. Choosing trees for their ornamental bark is becoming popular again

Silver birch Betula pendula with their bright stems

Tibetan cherry tree Prunus serrula with the high coppery shine.

But bark is much more than decoration, we use the bark from Cork oak Quercus suber for our wine bottle corks and placements amongst other uses. Other barks are used for rope and spices and even Asprin is derived from the bark of a Willow. For trees however their bark is a often the first to show signs of poor health, from fungal or bacterial diseases to drought or pesticides, the visual appearance of the bark is one of the first checks arboriculturalists make. Damage made by man or nature to the barks surface allows pests and disease in and prevent nutrients reaching the leaves, the phloem layer of tissue just below the bark is responsible for carrying food produced in the leaves by photosynthesis to the root.


Basidiomycotina (Basidiomycetes) is one of the major taxonomic groups of fungi which can have one of three roles in a forest;
• Saprobes – processing of decaying matter
• Pathogens – cause disease
• symbionts – mutually beneficial
understanding the impact of the fungi on a particular tree in a particular settings is complicated, fungi are overwhelmingly the most important pathogens of trees.


Bifurcation is a tree fork in the trunk giving rise to two roughly equal diameter branches. These forks are a common feature of tree crowns. Whilst not necessarily a problem, areas with bifurcation need close inspection due to their higher rate of failure.

Image credit to Wikipedia – Typical wood grain pattern at a mature tree fork, Slater et al.2014[1]


Bolling A term sometimes used to describe pollard heads, particularly when a tree is pollarded repeatedly. The initial point is then referred to as a Bolling.


Bottle-butt Perfect description but be careful if you choose to Google the term. As shown in the image below, bottle-butt is when excess broadening occurs or near the base of a tree, causing a distinct bottle shoulder shape. This can be caused by decay.


Bracing The use of rods or cables to restrain the movement between parts of a tree, more often used for veteran trees, or where public access is required.


• Primary. A first order branch arising from a stem.
• Lateral. A second order branch, subordinate to a primary branch or stem and bearing sub-lateral branches.
• Sub-lateral. A third order branch, subordinate to a lateral or primary branch, or stem and usually bearing only twigs.


Branch bark ridge and branch collar
The bark ridge it a strip of raised bark seen at the top of a join from a branch to a stem.
Branch collar is a visible swelling formed at the base of a branch.

Image credit to Wikipedia – A branch collar on a common oak

Both are important when pruning, so as not to damage the tree.


Brown-rot A type of wood decay in which cellulose is degraded, while lignin is only modified.


Buckling Another sign of stress in the buttress area, similar to bottle-butt, usually caused by compression due to weather or environmental stresses. The adaptive growth gives rise to a ring-like bulge.