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To obtain high prices Leucospermum cut flowers are required to have long, straight and slender stems. In addition, the time of flowering is also important, with Nov. and Dec. being considered periods of high demand in Europe for Cape Flora products. Several cultivars grown commercially in South Africa are genetically inclined to produce shorter stems, whilst most late flowering cultivars from warm production areas also present a challenge to deliver sufficient stem length. The practice of disbudding to extend the marketing window, especially in warm areas, likewise results in shorter stems the following season. To increase the stem length plant growth regulators were applied to single stems of Leucospermum 'Succession II' and 'Soleil' at Arnelia Farms, Hopefield, South Africa. Seven treatments were applied at five different times following pruning, at two weekly intervals. Shoot growth was monitored, while the duration of the harvest period and inflorescence quality was also recorded. The stem length was found to have increased in stems of all treatments compared to the control, for both cultivars. In 'Succession II' five applications of the 100 mg L-1 benzyladenine (BA) and gibberellic acid (GA3) combination extended the stem length by 200 mm compared to the control. In 'Soleil' five applications of 500 mg L-1 GA3 was responsible for a 200 mm stem length increase. Treated stems differed distinctly from that of the control in that a more upright growth manner was observed. The timing of application of the respective growth regulators is however considered important to obtain the required results. The use of growth regulators has shown commercially potential to increase stem length in Leucospermum.

Potted plants have grown in popularity as residential properties are becoming smaller and more people are living in apartments. Plants bought from chain store outlets serve as gifts and to beautify living spaces. Consumers consider containerised plants to last longer when compared to cut flowers. Containerised plants can be sold throughout the year, regardless of climatic conditions, as plants are often produced in greenhouses. However, desiccation in store is the primary cause of reduced quality as these plants require regular irrigation because of restricted root volumes. Water loss commences after the last irrigation is supplied by the grower. The rate of water loss is affected by temperature, light, relative humidity and air movement, during transport and instore. An interaction of these factors can seriously affect the water requirements of potted plants, especially during warm summers as is characteristic of the South African climate. The aim of this study is to extend the retail or postproduction (shelf) life of potted plants by evaluating novel watering methods to improve potted plants' accessibility to water in store and during the customer phase. Hydrangea macrophylla, Rosa 'Honora' and Spathiphyllum 'Sweet Rocco' with a current guarantee shelf life of 8, 10 and 21 days respectively were used. Four treatments (WaterWick, Aquastick, Aqua Pad and Gel4Pots) and a control were evaluated (n=6). Plants were scored for quality and weighed daily up to day 8 of vase life, where after weights and scores were recorded every alternative day. The best shelf life was recorded in plants subjected to the WaterWick and Aquastick treatments where an adequate and continuous water supply allowed the shelf life to extend far beyond that of the current retail period. The commercial potential for both these applications should be explored further for the South African ornamental market, especially the Aquastick, as it is currently less expensive than the WaterWick.

Leucospermum exports from South Africa for the 2013/2014 season comprised 45% (number of stems) of the combined exports of Leucadendron, Leucospermum, and Protea. The determining quality parameter for Leucospermum cut flowers is stem length, with stems sold per centimetre stem length. Over production of short-stemmed Leucospermum cut flowers affect the South African fynbos market share negatively on the export market. Information on the physiology of shoot extension growth, the timing of appendage formation and factors which directly affect shoot length is limited for Leucospermum. Subsequently, shoot extension growth of Leucospermum 'Succession II' (L. lineare × L. cordifolium) and 'Soleil' (L. glabrum × L. cordifolium) was studied to establish its relationship to the timing of appendage formation in two contrasting production areas in South Africa (Hopefield, at 50 m altitude, with particularly warm dry coastal summers; Piketberg, approximately 66 km from Hopefield, but at 800 m altitude, displaying a more moderate, Mediterranean climate). For both regions, shoot extension growth was linear, following an initial lag phase. In all cases 50% or more of the final number of leaves per shoot was differentiated at ca 100 mm stem length. Stems were significantly more extended in the cooler production region of Bo-Piketberg compared to Hopefield and final stem length appears to be area dependent. This data serves as baseline to further studies which aim at evaluating the efficacy of exogenously applied plant growth regulators to increase the stem length of problematic Leucospermum cultivars in warm areas, as well as short-stemmed cultivars such as 'Jelena' produced in cooler areas, in both cases, without compromising flower quality.

Leucospermum cut flower stems are prone to chilling injury and leaf yellowing as a result of long-term cold storage below 4°C as is required when exporting Leucospermum by sea freight from South Africa to European markets. Potted plants of Leucospermum 'Memory' (L. cordifolium selection) and Leucospermum 'Rigoletto' (L. cordifolium × L. glabrum) were subjected to LED lighting (treatments included 'full', 'half' and 'no light' levels) and growth regulator treatments (500 mg L Promalin® and MaxCel™ respectively) to evaluate their efficacy for alleviating cold-induced injuries after a three week cold storage period. The plants subjected to a 'full light' LED treatment showed a significant reduction in chilling injury and leaf yellowing in comparison to plants subjected to the 'no light' treatment. Promalin® and MaxCel™ showed no or little ability to reduce the associated postharvest cold storage disorders. It was concluded that LED at a light energy level of 25.03 ± 2.09 μmol m s was effective at reducing leaf yellowing and chilling injury. A range of Leucospermum cultivars should also be evaluated for its suitability to be placed in cold-storage with supplemented LED lighting.

Rising temperatures associated with global climate change may alter the physiology and phenology of Protea species and cultivars. Protea species are assumed to be well adapted to warm summers characteristic of their natural Mediterranean-type habitat, but their plasticity in responding to higher growth temperatures is not known. Using infrared lamps, a greenhouse-based temperature gradient was constructed, with temperatures ranging from ambient to ambient + 3.1 °C. Potted plants of Protea ‘Pink Ice’ (P. compacta R. Br × P. susannae Phill.) were grown at five positions along this gradient for 12 months under irrigation. Simultaneously, a field verification experiment in a nearby commercial ‘Pink Ice’ orchard was conducted under ambient temperature and ambient + 2.9 °C. Increased sclerophylly (leaf dry weight per unit area) with increasing temperature indicated leaf structural changes. While leaf area based gas exchange (net CO2 assimilation rate, stomatal conductance and dark respiration rate) did not differ across the temperature gradient, leaf weight based CO2 assimilation rate and dark respiration rate decreased significantly towards the upper end of the temperature range. The optimum temperature for net CO2 assimilation rate (Topt) showed seasonal adjustments, but increased in response to experimental warming only in the field experiment. Significant temperature elevation resulted in an earlier onset of spring bud break, but warming extended inflorescence initiation from the spring flush to the summer flush, leading to delayed flowering. Aboveground biomass allocation shifted from inflorescences to leaves and to a lesser degree to stems, with elevated temperatures, whereas root growth was stimulated in the middle of the warming range. The results of this study suggest that elevated temperature may prolong the vegetative growth period in some Protea cultivars where water is not limiting, at the expense of flower production. This could have significant economic and marketing consequences for commercial cut flower production systems. The findings are also of significance to ecologists studying the responses of Proteaceae to climate change.