Many New Zealand Shrubs have branching patterns which are recognisably distinctive, but difficult to describe. Observations of the habit of shrubs and particularly of divaricating shrubs have suggested differences which could be used as the basis for a classification.

In a ‘normal’ shrub each new branch makes an acute angle with the branch it springs from, so that the pattern of branches is a three-dimensional spreading fan. In some extreme cases where new branches are set at a very narrow angle, the branches may all come to stand more or less erect and parallel to one another. This form of growth is known as fastigiate. If on the other hand the angle of divergence of secondary branches is as much as 90 degrees or more, the branchlets will grow amongst each other and become increasingly intermeshed to produce a twiggy shrub regardless of the structure which underlies that divaricating form. The term divaricating itself refers to the wide branching angle but it has come to be used of any tangled, appearance. In juvenile Sophora microphylla and Carpodetus serratus the factor mainly responsible for the divaricating appearance is the zig-zag nature of the branchlets, which change direction slightly at each node.

The following is not presented as exhaustive, but may be useful as a basis for critical observation and description of plant habits.

Classification

• (1) Normal branching (at an acute angle):

  • (a) with straight twigs e.g. Leptospermum scoparium.

  • (b) with zig-zag twigs e.g. juvenile Carpodetus serratus.

• (2) Branches set at a narrow angle to the parent axis and tending to be parallel (fastigiate) e.g. Coprosma areolata.

• (3) Branches set at right angles to the parent axis:

  • (a) branching distantly placed or lax e.g. Coprosma rotundifolia.

  • (b) branching close-set e.g. Coprosma propinqua, Coprosma rhamnoides.

  • (c) branching tends to be sympodial as there is regular die-back of the tips e.g. Coprosma crassifolia.

• (4) Branches reflexed at an angle of more than 90 degrees e.g. Coprosma acerosa.

The term ‘divaricating’ is used of all the types 1 (b), 3 (a), 3 (b), 3 (c) and 4 in the classification.

G. M. Taylor

page 15