I’ve spent most of winter with my head in various books and at my computer, researching for my new book, The Plant City. It feels like I have been indoors for months and I only emerged during Easter weekend. As a result, I’m not exactly feeling youthful and I’m more than a little jealous of my herbaceous perennials. How great would it be if we all could go to sleep for winter and wake up looking like a teenager?
Herbaceous perennials are smart cookies. During winter, they retreat underground allowing them to escape the ravages of the weather and hide completely from potential predators. They can live for a very long time but rarely look as old as they actually are because, before they sleep for winter, they form adventitious buds just below ground level. When the weather warms up, these adventitious buds burst into fresh, juvenile growth before they become fully functioning, reproductive adults again. As a result, they get to relive their teenage times repeatedly.
Unlike shrubs, herbaceous perennials do not retain above ground parts through winter and this means they have to initiate a full regrowth each year. Because of that, they reach a consistent height and their flowering time is extremely predictable. From a maintenance point of view, they’re very accommodating. In general, they compete very well with most weeds so, if you pack a border with them, they’ll crowd out the weeds. When they’ve finished flowering, you can remove the spent flowers heads and tidy up any vegetative growth which has died back if you want. I leave mine alone to do their own thing because, sometimes, you get a nice effect from frost and snow lying on the flower heads and vegetation.
Though they always reach the same height, they do increase in width each year. Eventually, you have a situation where the plant has outgrown its allotted space and the middle growth is looking more tired than the fresher growth at the outer edges. When this happens, you can lift the whole plant and carefully pull it apart into a number of new plants, each with roots attached. Discard the middle section and replant some of the new plants you have made. This method of propagation is known as division and you’ll probably have plants left over for your friends as well. Herbaceous plants are divided in spring or autumn every three to five years.
From a garden designer’s point of view, the predictable nature of herbaceous perennials means they are great to work with – if you can cope with the fact that they disappear for several months a year. However, I can always forgive them their vanishing acts when those fresh teenage shoots become adults and flower.
Whatever height, shape or colour you like, you can find a herbaceous perennial to please you and, because they don’t flower for as long as the seasonal bedding plants, you can appreciate them all the more. If you’re clever with planning, you’ll have herbaceous perennials in flower from early spring until late autumn. Check out my article on Gardenzine to discover some of my favourites for spectacular colour during every season.