Q Has adding compost to my clay soil stopped my grasses fowering?
Louisa, by email A
PIPPA SAYS I think you have correctly worked out the reason why your ornamental grasses aren’t flowering: nutrient imbalance. Levels of various nutrients can significantly influence how different plants grow and how well they perform. Materials such as well-rotted manure and garden compost play a really useful role in improving the structure of soil, such as your clay, and boosting plant growth. The relatively high levels of nitrogen they contain will certainly encourage lots of stems and foliage. However, this often happens at the expense of flowers or seeds/fruit.
I suggest you don’t add any more compost for a couple of years. Instead, apply sulphate of potash in early spring, then again in late summer each year. This should turn things around, but it may not be in the first year.