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Roses grown in a greenhouse with climate control

Maximum profit for rose growers with perfect climate

The South African company Morgan Roses, was founded in 1996, just outside the town of Warmbaths. Initially, it had naturally ventilated greenhouses covering an area of one hectare. The company has now expanded to encompass 4.5 hectares, producing about six million roses a year. Morgan Roses sells to the local market and exports to international markets, i.e. Western Europe, Eastern Europe, and the Middle East. During 2001, the average price for roses on the South African market was ZAR*) 0.72 each, while the average export price per rose amounted to ZAR 1.40. It would obviously be of great advantage for Morgan Roses if they were able to export a large percentage of their roses. The only thing keeping them from doing so was the difficulty in growing sufficient high quality roses to meet the quality standards and continuity of supply demanded by the export market. At the time, only about 40% of their roses met these standards.

Roses are graded according to stem length and bud size. Generally speaking, the market demand is for long-stem roses. In Eastern Europe, there is also a great demand for big buds (i.e. larger than 5 cm). The roses produced by Morgan Roses had, on average, stem lengths measuring 50 to 60 cm and never longer than 70 cm with buds sizes ranging from 3.5 to 4.5 cm. Although these were acceptable quality roses, they were by no means top quality. Export roses are priced according to stem length, averaging ZAR 0.023 per cm. Producing roses that are 10 cm longer would therefore result in an additional income of ZAR 0.23 per rose. If, at the same time, the bud size could be increased, then the roses would naturally appeal to a much larger market segment.

Controlled climate – key to the success

Le problème de base de l’entreprise est de
maintenir des conditions climatiques
idéales pour les roses dans ses serres ventilées
naturellement. La température
idéale pour les roses est de 27 °C, avec un
taux d’humidité de 60-70%. Dans la région
deWarmbaths, la température
maximale est de 34,7 °C en été et le taux
d’humidité à la mi-journée est en moyenne
de 45%. Dans ces conditions, il est
impossible d’augmenter la production de
roses et d’en améliorer la qualité. Encore
plus grave, les conditions climatiques à
l’intérieur des serres ventilées naturellement
étaient à peine meilleures. La température
atteignait fréquemment 34 °C et
le système de brumisation ne parvenait
pas à faire grimper le taux d’humidité audelà
de 50% sans mouiller les roses. Les
rosiers ont été soumis à des conditions
difficiles entraînant des roses à tige courte
et à petit bouton. De plus, les roses qui
ont poussé pendant l’été ont produit des
boutons creux.

Cool solution

In order to alleviate the problem, Morgan Roses approached Munters for assistance in designing their new 3,200- sq.-meter greenhouse. To enable them to provide a greenhouse climate close to the ideal for roses (27°C, 60-70% RH), Munters recommended installation of the CELdek system. Plants were subsequently transplanted from the existing naturally ventilated greenhouses to the new greenhouse with CELdek system. The outcome was simply astonishing. The Bianca cultivar plants had produced roses with an average stem length of 60-70 cm, with 80 cm not being uncommon. The bud size increased to five cm on average. Even more impressive was the fact that nearly all the roses produced in the new greenhouse were of export quality.


  • Reduce the temperature inside the greenhouse by 7°C
  • Remove moisture and reduce humidity during night time
  • Achieve high quality and appearance roses even through knuckle cutting
  • Improve the control of the house environment, and limit the temperature and humidity extremes
  • Eliminate the occurrence of powdery mildew and red-spider mite
  • Reduce power consumption
  • Guarantee maximum profit