Vegetative and floral shoot development of Zantedeschia ‘Black Magic’

Abstract

Vegetative and floral development at the apical meristem of Zantedeschia Spreng. ‘Black Magic’ aff. Z. pentlandii (Wats.) Wittm. [syn. Richardia pentlandii Wats.] was traced through multiple seasons of growth. The growth habit was sympodial. For vegetative shoots, seven new structures were laid down on the primary axis for each season to form the over-wintering bud, from which all of the subsequent season’s visible growth arose. When a previously vegetative shoot flowered, the flower (spathe and spadix) arose directly from the apical meristem of the over-wintering bud which, at the time of planting (September; spring), was vegetative. At planting this over-wintering bud comprised six cataphylls, two leaf initials, and the as yet undifferentiated apex. For floral shoots, the terminal inflorescence consumed the original vegetative axis and a continuation shoot arose in the axil of the first leaf, the oldest leaf on the primary axis. While only the first three or four leaves of this continuation shoot actually emerged during the current season, a total of 14 structures were formed on the axis by mid-March (autumn). In the continuation bud of flowering plants a 4 month period of endo-dormancy occurred from mid-January through to mid-May (summer to late autumn). There was an apparent overlap between the onset of endo-dormancy of the continuation bud (January/February), the period when new foliage had stopped appearing (February), and attainment of the maximum number of structures in the continuation bud (March). Growers are recommended to wait until dormancy is complete (June; winter) before replanting tubers for the purposes of early forcing.