Environmental control of bud formation and flowering of clonal Acacia baileyana F. Muell. for ornamental horticulture

Abstract

To study the temperature requirements for flowering, cuttings of A. baileyana were either transferred between different temperatures in controlled-environment growth cabinets, kept outside or in a shadehouse. Plants in the growth cabinets were transferred from a low (13/9˚C) to high (23/19˚C) temperature, from a high to low temperature, or kept at a constant intermediate (18/13˚C) temperature, and then transferred outside. Acacia baileyana required temperatures at or above a mean maximum of 18˚C and a minimum of 13˚C for bud formation, and at or below a mean maximum of 16˚C and a minimum of 9˚C for flowering. Nearly twice the number of plants transferred from high to low temperature flowered compared with outside plants. Bud formation was inhibited at a temperature of 13˚C maximum and 9˚C minimum. Large buds dropped when the temperature was above 18˚C maximum and 13˚C minimum, indicating that the timing of plant transfer between the warm and cool conditions should be when the buds are at a medium size. Light intensity also affected flowering, with less than half the number of plants flowering in the shadehouse compared with outside. Plants transferred from high to low temperature were induced to flower 4 months earlier than outside plants by manipulating the temperature. Flowering cut stems or pot plants of A. baileyana could be produced for Mother’s Day in May and for other key markets.