What is a Perennial ?
Summed up in a single phrase, a perennial is a plant that lives and flowers for a number of years leaving behind no woody structure each season. Examples of perennials would be Campanulas, Delphiniums, Heleniums, Hellebores and Rudbeckias. So, if you plant perennials you can expect a reliable splash of colour year on year which will only get better as the plants grow in size.
It might be helpful to contrast perennials with some other groups. I’ve not been too technical as in horticulture many of these terms are used quite loosely.
Annuals and Biennials
Annuals and biennials both grow, flower and then die. Annuals do all this in one year, whilst biennials grow leaf one season and then flower the next. There are a few plants that grow for several seasons before flowering and dying – these we call monocarpic.
This is not a form of biology, but reference to how tolerant of our winters. Perennials can be either hardy (which we grow), half hardy (in need of some protection over winter) or tender (will die if exposed to the cold).
A subgroup of the perennials which overwinter by retreating to an underground swollen structure.
These are just a horticultural grouping, mainly comprising of little perennials from mountain regions
Shrubs and Trees
Plants that live and flower for a number of years, leaving behind an incremental woody structure as they grow. Trees contrast with shrubs by investing a more significant amount of woody material in one or more trunks.