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References Andre J P (2000) Heterogeneous, branched, zigzag and circu- lar vessels: unexpected but frequent forms of tracheary ele- ment files: description - localization – formation; In: Savidge R A, Barnett J R & Napier R (ed.s) Cell and molecular biology of wood formation; Experimental Biology Reviews. Oxford, UK: BIOS Scientific Publishers Ltd. pp. 387-395. Jaffe M J (1973) Thigmomorphogenesis: The response of plant growth and development to mechanical stimulation; Planta 114, 143-157. Hejnowicz Z & Kurcry´nska E U (1987) Occurrence of circular vessels above axillary buds in stems of woody plants; Acta Societatis Botanicorum Poloniae 56, 415-419. Lev-Yadun S & Aloni R (1990) Vascular differentiation in branch junctions of trees: circular patterns and functional significance; Trees: Structure and Function 4, 49-54. Slater D & Ennos A R (2013) Determining the mechanical proper ties of hazel forks by testing their component par ts; Trees: Structure and Function 27 (6), 1515-1524. Slater D, Bradley R S, Withers P J & Ennos A R (2014) The anatomy and grain pattern in forks of hazel (Corylus avellana L.) and other tree species; Trees: Structure and Function 28 (5), 1437-1448. Slater D & Ennos A R (2015a) The level of occlusion of includ- ed bark affects the strength of bifurcations in hazel (Corylus avellana L.); Journal of Arboriculture and Urban Forestry 41 (4), 194-207. Slater D & Ennos A R (2015b) Interlocking wood grain pat- terns provide improved wood strength proper ties in forks of hazel (Corylus avellana L.); Arboricultural Journal 37, 21-32. Slater D (2016) Assessment of Tree Forks; Course notes available from the Arboricultural Association, UK. Slater D (2017) The association between natural braces and the development of bark-included junctions in trees; Arboricultural Journal – currently under review. Telewski F W (2006) A unified hypothesis of mechanopercep- tion in plants; American Journal of Botany 93, 1466-76. (that I will be writing up as an academic paper) it was the Leylandii that was reported as the most prone to bark-in- cluded failures in the UK; understanding natural bracing gives a coherent explanation of why that happens so often. Now that this process is understood, individual trees can be checked for this flaw arising in them. Figure 5 gives an outline of the process of natural bracing, bark inclusion formation, and then natural brace loss and fail- ure in a poorly-formed scale-needled conifer. Further research is needed in a number of areas. One of our BSc (Hons) students this year has found natural bracing to be more common and more persistent in semi-mature lindens (Tilia spp.) compared with Norway maple trees (Acer platanoides), explaining the higher failure rate of bark-included junctions in the latter. We hope to contribute further to this new research area now that this mechanism for the formation of bark-included junctions has been found. In the meantime, practitioners can refer to the "Assessment of Tree Forks" publication (see References) as guidance on how to "read" tree forks from their mor- phology and how to classify natural braces formed in trees. Many of the arborists I have trained have really enjoyed these new findings, for natural braces are something tangible that can be found in many of our urban trees and they help to explain the morphology of tree forks in a straightforward way. I have written this article to encourage you to become a "natural brace spotter" too. It may well change not only how you look at trees, but also how you prune them. Figure 5 Typical failure cycle of a conifer with double leaders, associated with natural bracing. Self-shading removes natural braces. Junction bulges Young Natural braces develop A bark included junction develops FAILURE!