"Bio-fertilization works in pelargonium"

As organic farming continues to traverse the road to success, organic fertilizer can also prove its usefulness for ornamental plants. The Weihenstephan-Triesdorf University of Applied Sciences reported their success in attaining good product marketability in their experiments with pelargoniums.

by Hans Peter Haas

Organic cultivation of pelargoniums, economically feasible?
While the production of organic fruit and vegetables has long been established, producers of ornamental plants are rather sceptical about this development and doubt, above all, its economic feasibility. The restructuring of production will result in a massive cut in the usual work processes. For the most part, the experience and the knowledge of whether the required quality standards can be met will be lacking. Many cultures do not have reliable cultivation instructions. Weihenstephan-Triesdorf University of Applied Sciences has sought to remedy that situation and has been studying this topic for a long time.


College experiment with organic fertilisation: Despite different growth results, the majority of geranium plants proved to be in good quality.

A college is cultivating geranium varieties following the guidelines for organic production
Among other things, Pelargonium peltatum of the cultivars ‘Grandeur Bright Dark Red’ and ‘Calliope Dark Red’ were cultivated according to the guidelines of organic production. The peat-reduced bio-substrates made by Jiffy International AS and Gramoflor GmbH & Co. KG were used as a culture substrate. The pelargoniums were potted in the eighth calendar week in a 13 cm Teku VTG growing pot, which according to the manufacturer possesses a capacity of 0.84 litres of substrate. The fertilization was carried out as full stockage with a nitrogen-content based on 650 milligrams of nitrogen (N) per litre of substrate. The organic fertilizers used included phyto-grit (mainly from corn), neem cake, DCM Eco-Xtra1, DCM Eco-Plant 7 and sheep wool pellets in combination with Eco Fos. Osmocote Exakt 3-4 M was used for testing purposes. Pelargonium fertilizers were added to the substrates before the start of the test.

Good marketability for pelargoniums – with the exception of those with sheep wool fertilization
The photos above show plants that are ready to be sold after eleven weeks of cultivation. Despite different growth results, the majority of pelargonium plants presented remained in good quality. An exception to that were the plants that had been fertilized with sheep wool pellets plus Eco Fos. Here the plants were consistently smaller and had fewer flowers. In addition, the pelargoniums of the ‘Calliope Dark Red’ variety showed clear leaf whitening and were therefore classified as not sellable. The evaluation of plant growth based on the organic substrates used revealed significant differences in some growth parameters, which, however, did not affect the assessment of the marketability of pelargonium.

Conclusion of the Pelargonium experiment: full stockage possible
Pelargonium cultivation based on guidelines for organic cultivation was successful. The marketability of the majority of the plants at the time of sale proved to be very good.

A full supply of nutrients presented itself as a possible alternative for geraniums to basic fertilizer plus liquid post-fertilization. However, the exact knowledge of the nutrient requirements of the culture is required, in some cases even a variety-specific approach is required.

In the case of full stockage with organic fertilizers, the greatest difficulty is estimating the availability of nitrogen in terms of time and quantity, especially since the fertilizer is affected by the composition of the substrate as well. The mosquito infestation can spike by using solid organic fertilizers. The organic fertilizer “neem cake” did not have a positive side effect in the regulation of the fungus gnats. Watering treatments with NeemAzal, however, can be recommended.

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