Thread: Nature of Ebony Wood - Heartwood Formation

Nature of Ebony Wood - Heartwood Formation

My suggestion recently that another dark wood may have been an ebony (What is this timber) provides me an opportunity to elaborate, and share some pics of an Australian ebony with interesting features referred to as "Phytoallexin* induced heartwood formation”. I better explain lest you roll your eyes and seek solace elsewhere.

This effect is not peculiar to the ebonies but happens in MANY genera and species. The effects and causes are often species specific and the results (odours, colours produced and their appearance and location etc) are also species specific. Its evident in some spalted woods but also in ebony heartwood formation, shown below.

This ebony example, a species called small leaf ebony, (Diospyros humilis) is a small Australian tree, from the dry scrubs of northern Australia, has a black scaly bark. Its orange fruit (about 4-5 mm in diam) look just like mini persimmons, which of course they are related to! However, even a large diameter tree, say 60 cm in diam., will often only have a small black heartwood. Smaller damaged trees will often have much more heartwood. Sadly the heartwood is very fractile, easily splitting and breaking. It has a pale sapwood and pink intermediate woood and black heartwood (sometimes striped with paler bands). The genus Diospyros was once called Maba.

Other Diospyros species (most Australian, and many from overseas) show the same, small or no heartwood or sometimes a curiously dispersed heartwood, In parts of the world heartwood formation is induced deliberately by damaging the cambium (beating the stem) or naturally if and when fungal or other infection occur through tree damage.

Some examples below are chosen to illustrate this peculiar response of plants to external challenges, a response which we love to see in wood while working on projects
Euge

PS: This has been published in 'World of Wood' the bimonthly journal of the International Wood Collectors Society

* Phytoalexins are (usually) antimicrobial substances produced by plants in response to infection by a pathogen or elicitation by abiotic agents eg toxic elements mercuric salts. Even sweet potato slices infected with some fungi or treated with a mercury salt (an elicitor or stimuant) will produce toxic metabolites (certain terpenes), possibly to protect themselves or slow growth of the invading organism.

SL EBONY.jpg
Above : small diam log 10-12 cm dia, with bark and no end coating, Showing islets of induced heartwood between sapwood and intermediate wood pluse well formed black heartwood

SL ebony 2.jpg

Above: Larger Log of 20-25 cm dia (end-coated with a lacquer) with small heartwood but islets of black induced heartwood in sapwood and intermediate wood

ebony branch .jpg Ebony other.jpg

Above: Broken branch inside break (left) and outside (right) of same piece of wood showing where and how the heartwood formed from wound.