Evaluation of a Selection of South African Plectranthus Species as Indoor Plants

1. Evaluation of a Selection of South African PlectranthusSpecies as Indoor Plants Ryan J. Cheng and Professor Marilyn Daly Department of Biological Sciences, York College of Pennsylvania Figure 10. P. ‘Cape Angel Dark Pink’. METHODS RESULTS DISCUSSION • Table 1. • These are the 10 top performers that earned above average scores of >4 out of a possible 5 points for overall season performance. • 7 of the top 10 performers were cultivated varieties. • *This would be expected since cultivated varieties have been carefully selected for their horticultural qualities. • 3 of the top 10 performers were straight species. • *These results suggests that while cultivated varieties of Plectranthus have superior horticultural qualities that make them excellent house plants, there are also species plants that should also be considered as viable indoor plants. • Figures 3, 4, 5. • These are duplicate cultivars of P. fruticosus‘James’ from two sources—one in SA and one in the US. • Both scored equally well, thus one might conclude that this confirms the horticultural value of this cultivar. • However, even though they were supposed to be the same cultivar and their performance scores were equal, their foliage color and size of the plants differed between plants from the two sources. • P. fruticosus ‘James’ from New Plant Nursery displayed yellow-green foliage and a shorter size compared to the P. fruticosus‘James’ from Huntington Botanical Garden which exhibited a dark-green foliage and a taller stature. • *These observations suggest that these two plants are not the same cultivated variety, but both have very good horticultural qualities. • Figures 6, 7. • This compares the straight species P. verticillatus to the cultivated variety P. verticillatus‘Barberton’. • Both samples had almost identical scores in all categories each week and in their overall season performances. • Their habits, foliage, and flowers looked identical to each other. • *These results question whether ‘Barberton’ is a unique cultivar or if this sample was indeed ‘Barberton’. • Figures 8, 9. • P. ‘Mona Lavender’, P. ‘Cape Angel Edelblau’, and P. ‘Cape Angel Dark Pink’ are crosses between P. hillardiae X saccatus (Brits 2001, Jaarsveld 2006). • Both P.‘Monal Lavender’ and P. ‘Cape Angel Edelblau’ performed very well. P. ‘Mona Lavender’ obtained a higher Interest score due to its longer period of flowering. P. ‘Cape Angel Edelblau’ achieved a higher Health score due to its higher resistance to diseases and pest. • P. ‘Cape Angel Dark Pink’ was not among the top performers. It achieved an interest score which was very similar to the other two related cultivars, but its health score was low because it was not as vigorous as the other two. • *These results suggest that there are important performance differences between related cultivated varieties and therefore one should make selections carefully. USDA Plant Permit Table 1. Top 10 – Overall Season Performance Figure 1. P. ‘Mona Lavender’ in YCP greenhouse. Received Cuttings From U.S. and S.A. Sources INTRODUCTION • South Africa is renowned for its plant biological diversity and many South African plants have been cultivated through the centuries. Plectranthusverticillatus, the common “Swedish Ivy” houseplant, was the first species of Plectranthus brought to and popularized in the United States in 1960. However, most of the 53 South African Plectranthusspecies are relatively unknown in cultivation (Jaarsveld 2006). • Plectranthusspecies have a variety of growth habits ranging from upright and shrubby bushes to sprawling ground covers. These habits suggest how Plectranthus can be used in cultivation—in hanging baskets, cascading over the edges of pots, or growing upright in containers. • MostPlectranthusare shade-tolerant, forest floor species while some species are succulent and semi-drought tolerant and thrive in full sun. Plectranthus are easy to propagate from seeds and cuttings (Brits 2001) and require very little care. These qualities characterize qualites of successful house plants.   • Plants must be objectively evaluated prior to being promoted commercially for garden or indoor use. Plant trials provide an objective mechanism to evaluate a plant’s performance. Important performance criteria for indoor plants are: vigor, foliage interests, resistance to disease and pests, and habit. Flowers, although not necessary, are an added attraction. • This project evaluated 28 South African Plectranthus species and cultivars from South African and North American sources. The plant trial was conducted in the York College of Pennsylvania greenhouse from September 21, 2008 to January 10, 2009. Planted in soil-less mix in progressively larger containers:2.5 x 2.5 trays 7.6 cm pots 15.2 cm pots 1cuttings were obtained from Huntington Botanical Garden, California 2cuttings were obtained from New Plant Nursery, South Africa 3cuttings were obtained from Kirstenbosch Botanical Garden, South Africa 4cuttings were obtained from RKS Nursery, Pennsylvania Maintained and Evaluated in YCP Greenhouse EVALUATIONS Defined evaluation criteriaand assigned point values for each level of performance Figure 5. P. fruticosus‘James’ from New Plant. Nursery. Conducted weekly evaluations from: September 2008  January 2009 Evaluation Criteria and Percent Value Figure 3. Comparison of P. fruticosus‘James’ from Huntington Botanical Garden , California and New Plant Nursery, South Africa. Health Qualities Vigor 30% Resistance to disease and pests 20% Figure 4. P. fruticosus‘James’ from Huntington Botanical Garden. Total Health Score 50% CONCLUSIONS OBJECTIVE When choosing a Plectranthus for a house plant, one should consider its natural habit and habitat and select a plant for its specific horticultural qualities. Growers and consumers should obtain plants from reliable sources and be aware that there can be discrepancies in nomenclature. Horticultural Interest The objective of this project was to describe and evaluate the performance and horticultural qualities of 28 South African Plectranthus. Foliage Interest 40% Habit 5% Flower 5% Figure 7. P. verticillatusand P. verticillatus ‘Barberton’. Figure 6. Comparison of the species P. verticillatuswith the cultivated form P. verticillatus‘Barberton’. LITERATURE CITED • Brits, G.J., Selchau, J. and van Deuren, G. 2001. Indigenous Plectranthus(Lamiaceae) From South Africa as New Flowering Pot Plants. Acta Hort. 552:165-170. • Jaarsveld, E. 2006. The South African Plectranthus. 1st ed. Fernwood Press, Simon’s Town, South Africa. Total Horticultural Interest Score 50% FORMULAS: [(.30 x Vigor) + (.20 x Resistance)] = Health Qualities [(.40 x Foliage Interest) + (.05 x Habit) + (.05 Flower)] = Horticultural Interest (Health Qualities + Horticultural Interest) = Overall Season Score ACKNOWLEDGEMENTS I would like to thank Professor Marilyn Daly for her endless guidance, insight, and support for planning and completing this project. I would also like to thank Dr. Richard Daly and the YCP Biology department for their help and support of this project. I am also extend thanks to Huntington Botanical Garden, Kirstenbosch National Botanical Garden, New Plant Nursery, and RKS Greenhouses for supplying plant material for this project. Figure 9. P. ‘Cape Angel Edelblau’ Figure 2. YCP greenhouse with P. eckloniiin foreground. Figure 8. Comparison of 3 cultivated varieties bred From crosses between P. hilliardiexsaccatus.