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Studies of Dendrobium Sea Mary ‘Snow King’ investigated the effect of nutrient termination (1 Aug., 1 Sept., or 1 Oct.) and reapplication [at the beginning, in the middle, immediately after, or 2 weeks after (relative to cooling), or no nutrient reapplication] on growth and flowering, quantified cooling requirements (10, 13, 15, or 18 °C for 2 to 6 weeks) for flowering, and determined optimum nutrient termination (on the three above dates) and nutrient rate (0.33, 0.67, or 1.33 g•L-1 15N-2.3P-12.9K) for producing single-node cuttings. Regardless of reapplication stages, nutrient termination on 1 Oct. caused taller plants with more nodes, more leaves, more flowering nodes, more total flowers, and fewer aborted flowers than those being terminated earlier. Only buds protruding above 2 mm from pseudobulb surface showed differentiated floral structures. Plants with 1 Aug. nutrient termination had larger flower primordia than those with 1 Oct., indicating flower differentiated earlier or faster with an earlier nutrient termination. No reversion of reproductive to vegetative buds arose due to either late nutrient termination or resumption of nutrients during cooling. Interactions between temperature and cooling duration were significant on time required for anthesis and full flowering, recorded from either beginning or completion of cooling, average flower number per flowering node, and flower diameter. Increasing cooling duration from 2 to 6 weeks led plants to reach anthesis and full flowering faster after cooling; however, the increasing cooling duration actually extended total time for producing flowering crops. Increasing temperature from 10 to 15 °C accelerated flowering after cooling. Plants had more flowering nodes and total flowers when cooled at 10 to 15 °C than at 18 °C. The results suggest that 3 weeks of cooling at 13 or 15 °C produce quality flowering plants that require less time to reach flowering. Plants fertilized at 0.67 or 1.33 g•L-1 were taller with 18% more nodes and more leaves than those receiving 0.33 g•L-1. Increasing nutrient rate with prolonged supply to the plants caused more single-node cuttings to grow into vegetative shoots for propagation, fewer cuttings to transition to flowering nodes, and less flower abortion to occur.

Südafrikanische Iridaceae enthalten viele Gattungen mit hohem Potential als neue Zierpflanzen. Von Anfang 2005 bis 2007 fanden Untersuchungen an vier geophytischen Arten aus dem Kapländischen Florenreich statt. Den Gattungen Freesia, Sparaxis und Tritonia angehörend, wachsen diese auf der Südhemisphäre während des Winters heran und blühen im Frühjahr. Bei einer Anzucht im europäischen Herbst bzw. Winter könnten ihre niedrigen Temperaturansprüche für den zukünftigen Produzenten eine energiegünstige alternative Kultur bedeuten. Folgende Untersuchungsziele standen im Mittelpunkt: Export während der Dormanz der Knollen, Lagerbedingungen nach dem Export, Pflanzsätze zu verschiedenen Jahreszeiten in Deutschland und allgemeine Ansprüche an die Wachstumsfaktoren. Die Ergebnisse wurden durch regelmäßige Bonitur der Entwicklung der Knollen bzw. Pflanzen gewonnen. Das Nachvollziehen der Infloreszenzanlage erfolgte durch mikroskopische Untersuchungen des Apikalmeristems während des Wachstums. Der Export der Knollen war unkompliziert und ihre Dormanz konnte durch eine Lagerung bei über 20 °C weiter aufrechterhalten werden. Für eine erfolgreiche Blüte nach der Pflanzung stellte die Temperatur den entscheidenden Faktor dar. Die Arten zeigten sich unterschiedlich empfindlich, doch war eine Kulturtemperatur von 13 °C nachts notwendig, wenn die Temperaturen tags über 17 °C lagen. Während der Sommermonate wurden auf Grund der hohen Temperaturen die Infloreszenzen erst gar nicht angelegt oder abortiert. Die vorherrschenden niedrigen Lichtintensitäten der Wintermonate führten ebenfalls zu einem Infloreszenzabort oder einer verspäteten Anthese. Durch spezielle Lagerbehandlungen der Knollen konnte bei der Anzucht eine Reduzierung der Pflanzenhöhe und eine verbesserte Blühleistung erzielt werden. Zusammenfassend lässt sich ein großes Potential der untersuchten Arten für eine energiegünstige Produktion und eine Erweiterung des Herbst-/Wintersortiments an Topfpflanzen in Europa feststellen. / South African Iridaceae contain many genera with a high potential for new floricultural crops. From the beginning of 2005 until 2007, investigations on four geophytic species native to the Cape Floral Region were conducted. Belonging to the genera Freesia, Sparaxis and Tritonia, they are winter growing/spring flowering in the Southern Hemisphere. If forced as pot plants for the European autumn/winter months, their low temperature requirements during cultivation could represent substantial energy savings for the future grower. The investigations focused on the following aspects: export during the corm dormancy, storage conditions after export, forcing experiments in different seasons in Germany and general cultivation requirements. Results were obtained by regularly monitoring the corms and the plant development. Inflorescence initiation was determined by microscopic examination of the shoot apical meristem during the growing season. - The export of dormant corms was uncomplicated and their dormancy could be further maintained in subsequent storage in Berlin at temperatures above 20°C. Temperature was found to be the main criterion to successfully realise flowering after planting. The species varied in their sensitivity, but generally cultivation at 13°C at night was essential, with temperatures of 17°C and above possible during the day. During the Central European summer months, inflorescences in the terminal bud failed to completely develop or flower primordia were aborted due to the high temperatures present. Furthermore, the naturally low light intensities during the Central European winter months also led to inflorescence abortion or a delay in flowering of three species. A reduction in plant height and enhanced flowering could be achieved for some species by specific storage regimes. In conclusion, the investigated species displayed a great potential for an energy saving production system as well as for enriching the autumn/winter pot plant assortment in Europe.