Herbaceous perennials are plants that flower and then retreat below ground during the winter. They will reappear the following year to flower again. They flower at their best in the third year. After the third year it is recommended that you lift the root in the dormant season, split them and replant. They will continue to flower the following year as good as before. Herbaceous perennials are hungry plants so it is important to feed them using a product like fish blood and bone which is a good all round slow release food.
A top dressing of Gee Up farm yard manure can also be applied in the autumn or in spring. FYM feeds the plants and also acts as a weed suppressant whilst helping to reduce water loss from the soil.