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| Leaf quality in the propagation of roses | |
| By taking great care to maintain leaf quality during the propagation of roses, a higher survival rate and better quality are assured. The utilization of cuttings (single-node stem segment with a five leaflet leaf and an axillary bud is commonly used in propagating rose plants. Rooted cuttings are less expensive (€0,70 in Holland as against €1.1 for grafted young plants) and are suitable for cultivation in substrates such as stone wool and coco peat-perlite, increasingly used in intensive cultivation of cut-roses under greenhouse conditions. A further important aspect is that the market life of new cultivars has progressively decreased from 7 to 4 years. To assure high quality, growers need to use uniform stock of a certified variety and disease free. In the case of stem cuttings, growers should check that the original leaf is intact and healthy and that the root system is well developed with healthy white roots at the bottom of the plugs or containers. The primary shoot should be well developed and healthy (if not, the axillary bud should at least be out-growing). It is essential that these morphological parameters are uniform in a given batch of young plants. The quality of the leaves on the propagating material plays a determinant role in successful propagation and therefore the material is placed in optimal conditions after cutting. The first few days immediately after cutting are critical and water stress is avoided by providing an RH of 90-95% and shade screens to lower light and reduce leaf temperature. Air temperature is maintained at around 23-26°C. The rooting substrate needs to have good drainage and aeration to favour growth and avoid disease. After rooting and when the axillary bud has developed into a shoot, the RH is lowered to about 70°C to harden the leaves to reduce the risk of dessication at the moment of transplanting. After transplanting, the RH in the greenhouse is kept high for the first few days. The total cultivation area for cut-roses in the world was estimated at 13,000ha in 2003. Plants, grown at a density of 8 plants/mq are substituted on average every 5-6 years. From this it can be calculated that the annual world market for young plants (grown on their own roots or grafted) is about 200 million. “FlowerTech” Vol 7 2004 www.Hortiworld.nl For further information: E-mail Miguel.costa@wur.nl or vanderpol@pro-overburg.nl at Wageningen University. |
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