Why are my potted ianthus buds empty?

Hi Robert,

Sometimes this happens when there maybe a small caterpillar that sometimes will eat the flower before it comes out but you would normally see a little hole. Make sure you feed your dianthus with a fertiliser with plenty of potassium like Yates Yates Thrive Flower & Fruit Soluble Plant Food to ensure good flowering.If you see caterpillars then you can use a product called Dipel or a product called Success Ultra,both can be found in your local nursery or hardware.