Roses are real heavy feeders and need regular and, above all, precise fertilization over the summer so that they remain he althy and strong in growth and produce their beautiful flowers. However, the nutrient supply should be stopped by the end of June at the latest in order not to delay shoot maturity.
Should you fertilize roses in autumn?
Roses should be fertilized by the end of June at the latest so as not to endanger their winter hardiness. Autumn fertilization can lead to soft shoots that freeze in winter and promote disease. Instead, roses can be specifically fertilized with patent potash in August to increase their resistance.
Autumn fertilization endangers winter protection
Administering nutrients later than June endangers the winter hardiness of your roses, because the supply of nitrogen in particular encourages the plants to tirelessly develop new shoots and not allow the existing ones to mature in time. These shoots, which are too soft in winter, freeze in the cold season and are therefore lost and can even be dangerous to the rose: a plant weakened in this way is ultimately very susceptible to various pathogens, especially fungi. At best, the nutrients just seep into the ground.
Pile up roses with compost?
Roses should be piled up with soil over the winter to protect them against frost. Sometimes you read the advice to pile up the plants with compost instead so that they are still supplied with nutrients. However, this is not a particularly good idea, as the nutrients seeping out of the compost can give the rose a late growth spurt, especially in mild winters. However, these fresh shoots are doomed to die and also serve as a gateway for numerous pathogens.
Fertilization with patent potash by mid-August at the latest
However, there is a way to encourage roses to mature through targeted fertilization and thus make them more resistant to frost and other weather hazards. You can achieve this if you fertilize with Patentkali (€33.00 on Amazon) between the beginning and middle of August - but definitely not later, because then this strengthening will simply remain useless. By the way, the potassium-based fertilizer has another advantage: it increases resistance to various pests and rose diseases. Don't forget to water the roses thoroughly after potash fertilization so that the nutrients reach the roots quickly.
Tip
Fertilization with patent potash also makes sense in spring, because it makes both the leaf green and the flower colors stronger - the elements sulfur and magnesium, which are also contained in the potash fertilizer, have a positive effect on the foliage and flower color.
