The GARDENA gardening expert
The pot size and the plant sound as if they fit, Ms. K., and it is correct to make the root bales smaller before you repot. In addition, oleander already forms its buds in the spring. In this respect, you have done everything right so far. What remains is essentially optimising the growing conditions:
Use a mineral substrate for the oleander. I like to use the Citrus and Tub Plant Soil from frux with its high amounts of clay and pumice. Add slow-release fertilisers when potting (three grams per litre soil). Care for the plants in a container with water reservoir or on a tray where excess water may stand during the summer. The location with full sun and slightly airy to prevent fungus is important. It is possible that this year’s damp and every changing temperature summer weather attributed to this so that the oleander was not as lush as in previous years.
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