Cultivation information for ornamental plants

Additional light is an advantage for the early sets. However, light should not be provided for more than 16 hours per day (at least 8 hours of darkness). The optimum is 14 hours with a daylight sum of 60 klxh, which will shorten the cultivation time accordingly for at least the first 30 to 40 days of cultivation.

CO² fumigation can shorten the cultivation time by a further 8% (on average). The optimum concentration is 900-1100 ppm during light hours. Fumigation is not necessary at night as it has no effect.

At the start of cultivation, it is important to get N into the plant, as it has almost no N left in the substrate due to overwintering. It is important to ensure a high proportion of nitrate, as this is directly available to the plant. It is recommended to fertilise in a balanced or N-K emphasised way. With the blue varieties, it is important to ensure that fertilisers low in phosphorus are used, as phosphorus has a negative effect on the availability of AL sulphate.

We also recommend fertilising with iron at the start of cultivation, as early hydrangeas in particular can very quickly suffer from iron deficiency.

The average pH value of blue hydrangeas is 4.2 and we therefore recommend a one-off fertilisation with AL sulphate of 1.5% (15g/L water) within the first 3 to 4 weeks. (Please only use AL sulphate concentrations, not potassium alum).

Please spray the hydrangeas once against botrytis immediately after forcing, as early forcing can lead to rotting when the plants are new in the sap. Furthermore, treatment against snails is particularly beneficial for white hydrangeas.

In addition to Alar, Desmel has also proved effective as a good inhibitor in recent years, but it is important to pay attention to the concentrations. In hydrangeas, Desmel is authorised against leaf spot, which is very important due to the new PS law. Concentrations of 0.02 to 0.03% can be used to regulate length growth without any problems. The frequency and possible increase in concentration depends very much on the crop and climate management and the weather. We therefore recommend a slow approach to higher concentrations. Furthermore, you should stop using Desmel shortly before the petals are visible, as it can lead to flower discolouration.

We hope this has given you a good start to the hydrangea season. If you have any further questions on the above or other topics, please do not hesitate to contact us. Please understand that these are only recommendations and that we cannot accept any liability in the event of damage.