Similar heights, different heads

While the young ones are shorter, mature quiver trees usually don’t differ dramatically in height, the type overview also including height as descriptor. All trees, wood-producing or not (like aloes and palms), are associated with typical height ranges per species.

These species descriptive heights become stretched and less meaningful when providing for the unusual specimens grown in atypical conditions. There is but one tree specimen living today and maybe another of all time, crowning the height achievement of its species: the species "Olympic" record holder. Unfortunately this champion is not a very useful choice for describing the tree in a field guide.

Imagine the age, mass, girth (at what height?), leaves (size and number), flowers (numerous options) and fruit (mass, colour, dimensions, sugar content) competitions that would ensue if indigenous forests got this idea into their trunks. And all the scandals from hybridisation, genetic modification, commercial plantations and illegal chemicals that would explode in the media!

Getting back to the simple matter of tree height, the exceptions merely prove the rules: Height ranges from natural (and artificial?) bonsai conditions to the remarkable giants that get depicted in coffee table books on that subject.

Primary tree growth, the elongation of the stems (and roots) slows down eventually for all species with age. Trees do not have a clear-cut maturity age around the end of adolescence like people and animals for whom there is no height increases at all upon reaching their specific mature age cut-off. Tree growth reduces gradually, like approaching an asymptote or limit determined by prevailing conditions.

Coates Palgrave (2002) in a general tree book gives Aloidendron dichotomum heights as 3 m to 5 m, occasionally 7 m and calls it a massive aloe, while using much greater heights when calling other "proper" trees large. Reynolds (1974) in a book dedicated to aloes gives a range from 6 m to 9 m, calling them tall trees. Mannheimer and Curtis (2009) say up to 5 m but occasionally up to 9 m, dealing with trees in Namibia. Jeppe (1969) writing on aloes has it as 3,5 m to 4,5 m. Van Wyk and Van Wyk (1997) only call the quiver tree a small tree giving no measurements in their tree book, while Van Wyk and Smith (2003) in an aloes book only say it is a tree aloe.

All writers choose contexts and conventions appropriate to their particular publication objectives, aided by measurements where deemed necessary. The measurements always exceed adjective precision and accuracy, but not descriptive depth or variety. Unless one wants to produce the dreary data base that would ensue from the premises that everything in existence can be measured and should be described in those terms.

Every particular field work exercise is by nature never exhaustive, while often exhausting. The specimens measured and the regions visited can never be identical, even time differences defy project congruence (Wikipedia).