Years ago, perhaps as far back as 1985, Anne Jenner conducted a census of HPS members’ favourite plants. To her surprise, euphorbias topped the list. I don't think their popularity has decreased since then. Or maybe they simply haven’t died out.
Euphorbia is a very large genus within the Euphorbiaceae family, encompassing a wide variety of forms such as annuals, perennials, succulents, and even trees. They can be found worldwide, sometimes behaving like weeds. Some are evergreen, others herbaceous, and some are popular as houseplants, like poinsettias and crown of thorns.
In gardens, euphorbias are primarily grown for three reasons: their usually spring-flowering greenish-yellow blooms, their architectural forms (such as the dramatic caper spurge, Euphorbia lathyris), and their foliage. They mostly come from dry or seasonally dry environments, resulting in several useful attributes—drought tolerance, pale foliage that reflects solar radiation, and winter activeness. However, they don’t live forever, often becoming old and woody, looking disheveled and thin on top—much like old men. To propagate them, I take cuttings from small side shoots that grow below mature seed heads. Almost all common garden forms have a pervasive, heavy scent of honey.
Euphorbia characias: A Mediterranean Marvel
One of the most important species to me is **Euphorbia characias**. Typically Mediterranean, these plants come from the east (SW France to Turkey) with yellower flowers (subspecies wulfenii) and the west Mediterranean (Portugal to Crete) with green flowers (subspecies characias). Britain’s climate suits them well; it’s not as cold as the Mediterranean in winter, and they cope with wet summers, though not so well in Cornwall, Kerry, and Kintyre. They thrive in dry shade under trees, particularly if moderate light penetrates during the day. A montane form of the western subspecies, called ‘Portuguese Velvet’, is squat and hairy, and it survived the harsh winter of 2010-2011 when all my other kinds died.
Their shape is a strongly textured ball about a metre high, with leaves held on the branches like a bottlebrush. In a Mediterranean climate, where winters are wet and summers are dry, these plants have evolved to flower from winter onwards, which is very cheering even in December when the branch tops begin to nod in preparation for the formation of flower heads. The plants last between 3 to 8 years, after which they become unprepossessing or die. They self-seed readily, and on a hot, dry August day, you can hear the seeds shooting from the dry carapace-like pericarps. The seedlings are easily managed, and sometimes a really good form emerges, giving rise to named forms like ‘Jimmy Platt’, ‘Blue Wonder’, ‘Lambrook Gold’, and more. Currently, I’m most enthusiastic about ‘BQ’ (my naming), which I found planted on the edge of a B&Q car park.
Variegated and Hybrid Euphorbias
I’ve tried ten variegated cultivars of euphorbias, but these forms are usually smaller, weaker, and tend to succumb in winter. During the RHS Trial of Euphorbias for the AGM at Wisley, every variegated form failed, including ‘Silver Swan’, a Notcutts variety from Suffolk. Two years ago, I was given three young plants rooted from the original stock to trial myself, and they have done well, surviving two winters in my alkaline Lias clay soil.
**Euphorbia amygdaloides** and its hybrid **Euphorbia x martinii** (a cross with E. characias) are also noteworthy. E. amygdaloides, a British native, hybridizes easily with E. characias. Among these hybrids, **Euphorbia amygdaloides var. robbiae** (Mrs. Robb’s hat) stands out. It provides effective ground cover in dense, dark shade and is easily managed when it spreads.
Unique Flower Structure and Care
Euphorbia flowers are distinctive, often lacking petals but featuring ornamental nectar-secreting glands that give the flowers color and a honeyed perfume. The flower heads, known as cyathiums, are backed by bracts that add to the plant’s visual appeal.
When handling euphorbias, it’s important to cover your skin and wear glasses, as the milky sap can cause excruciating pain if it gets in your eyes.
Cultivating Euphorbias
There are two tender species worth the trouble of growing: **Euphorbia marginata**, a variegated annual from North America, and **Euphorbia hypericifolia**, a tender perennial from the Caribbean. The latter needs to be kept in a pot and moved inside over winter, as it requires more warmth than just being frost-free.
Finally, two ‘shrubby’ species are essential for year-round flowering: **Euphorbia ceratostigma** and **Euphorbia margalidiana**. Both have greenish-yellow flowers and can grow to about 1.5 meters in diameter, though they can get bigger in better soil.
Conclusion
Euphorbias are a diverse and fascinating genus that offers a variety of forms and uses in the garden. From drought tolerance to unique flower structures, they bring a wealth of benefits to any garden. Despite some challenges, their beauty and resilience make them a worthy addition to any plant collection.
