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The common and prevalent belief is that potash fertilization protects roses from frost damage. Whether in textbooks or as a tip from the rose grower: everywhere potash is recommended for roses. Applied in late summer or autumn, Kali should be a good protection against the winter and the associated possible frost damage.
Is potash fertilization really useful for roses?
Fertilization with Patentkali in August should protect the roses from frost damage in winter
But there are also critical voices questioning this doctrine. One of them belongs to Heiko Hübscher, the gardening director of the rose garden Zweibrücken. In an interview he explains why he does not consider potash fertilization to be useful.
Heiko Hübscher is the gardening director of the Rosengarten Zweibrücken
Roses are traditionally fertilized with patent potassium in August for better frost resistance. How do you feel about this?
We have not been giving potassium for more than 14 years and have not suffered frost damage more than before - with winter temperatures of 18 degrees Celsius and very unfavorable temperature changes. Because of these personal experiences I doubt, as well as other rose gardeners from cold regions, this recommendation. In the literature it is often only: "can increase the frost hardness". Because scientifically proven it is not! I suspect that one is writing off the other and nobody dares to break the circle. Would he be blamed for possible frost damage to the roses?
Is a summery potassium fertilizer even up to date?
If you believe it, do it. But please note that the associated sulfur intake (often more than 42 percent) can acidify the soil and disrupt nutrient uptake. Therefore, regular fertilization with patent kali should also be followed by a laxate at intervals. We pay attention to a balanced nutrient concentration in our fertilizers - preferably slightly nitrogen-reduced and in spring a bit calibetonter. Thus, mature shoots form, which are frost hardy from the outset.