Raspberries Need Phosphorus and Potassium in Autumn, Not Nitrogen
After the summer harvest, raspberry bushes should get a fertiliser richer in phosphorus and potassium, while nitrogen should be limited. Nitrogen encourages new shoots that may not have time to mature before frost.
Gardeners who grow raspberries still need to look after the bushes once the summer harvest is over. In autumn it is important to supply nutrients that help the plants prepare for winter and for the start of the next season. Many gardeners make a mistake with fertiliser, because the best choice for raspberries in autumn differs from what suits them earlier in the year.
Which fertiliser to use
At this time of year, a fertiliser with a higher content of phosphorus and potassium is especially useful. These nutrients help plants get ready for winter and improve their hardiness in the cold.
Why nitrogen should be limited
Nitrogen stimulates the growth of new shoots, but in autumn this can backfire. If a plant keeps actively producing new shoots as winter approaches, they may not have enough time to mature and prepare properly for the cold. For this reason, gardeners are advised not to overdo nitrogen in autumn.
When and how to feed
The suitable period for feeding raspberries is September and the beginning of October, while the soil is still sufficiently warm. The fertiliser should be scattered over the root zone of the bush and lightly worked into the soil, taking care not to damage the roots.
Compost or humus can also be added in autumn. They provide extra organic matter, may help retain moisture and can improve soil structure. Organic materials can also serve as mulch around the bushes.
The key point is not simply to "feed" raspberries with any fertiliser, but to pick one that matches the plant's needs in the given season: phosphorus and potassium help it prepare for the next growing period, while too much nitrogen can trigger unwanted new shoot growth.
