Towards a numerical definition for divaricate (interlaced small‐leaved) shrubs

Shoot architecture (leaf size, shape, and arrangement; branch frequency, length, and angles; number of apices) was measured on 49 plants representing 24 species of divaricate and non‐divaricate shrubs and juvenile trees from Canterbury. A clustering program created two different groups for the divaricate species, as well as a separate group for small‐leaved shrubs with many closely spaced leaves usually on two‐dimensional fans. The variables that best separated the divaricate and non‐divaricate species were leaf width, internode size relative to leaf width, and branch angles. An index was constructed, using these variables, which is fast to measure and correlates well with perceived degree of divarication. A formal definition is proposed for New Zealand divaricate plants including: (1) many interlaced, wide‐angled (mean >60°) branches; (2) small leaves (<60 mm 2 ) widely spaced on the branches (mean distance between leaves is >2× leaf width); and (3) larger leaves towards the interior of the plant (inner leaves usually >1.4× larger than outer ones).