Almost all the plants at Heronswood are perennials
Not herbaceous perennials, but perennials nevertheless. Woody trees, shrubs and vines are perennial, because they live for multiple years but when we hear the word “perennial”, we tend to think herbaceous. Herbaceous plants are non-woody, but not all are perennial. While the many familiar asters, geraniums and hostas are perennial, coming back year after year, some herbaceous plants are annual, completing their brief life cycle in under a year. The word “herbaceous” therefore refers to their physical form – its opposite is “woody” – while “perennial” refers to their life cycle, which continues from year to year.
So, what are biennials? The clue is in the name. Like “perennial”, the word refers to a life cycle, but the “bi” bit tells you they only last for two years. It’s usually a lot less than two years. Take the common foxglove (Digitalis purpurea), one of our best-known biennials. Seeds germinate in spring and the resulting plants grow through summer, spending the winter as a crown of leaves. The following spring, they flower, set seed and are dead by summer – a life lived in 18 months only. Biennials are much less common than perennials and annuals, but they bring a lot to the garden. Many vegetables are biennial: carrots, cabbages, cauliflower, beets etc. Ornamental biennials include wallflowers, hollyhocks, sweet Williams and honesty.
The star of this email is also a biennial, Angelica gigas. With stems as tall as me in a brooding, sultry purple, topped by huge umbrella-like flower clusters, this East Asian plant departs this world on a high note. Angelica spends its first year as an untidy cluster of unremarkable green leaves, but in year two, it rapidly extends a stem upwards in order to flower and set seed. It’s at this point that it finally makes its presence known, becoming the focal point of our Perennial Borders. The individual flowers are small but their rich vinous coloration exudes luxury. This show has no encore – the plant will die after setting seed – so come to Heronswood and see this diva before she fades. And if you’re not already tired of my ponderings, join me and lead gardener Matt Jevnikar for Show & Tell at 11am, Friday, Saturday and Sunday in the Heronswood parking lot. We’ll delve into the back stories of some of our most beautiful and interesting plants and answer any horticultural questions you may have.
– Dr. Ross Bayton, Asst. Director