Diverse Euphorbia

Sunday, 01 July 2012

Euphorbia pulcherrima

Spying the first of the showy flowers of the season on my shrubby poinsettia (Euphorbia pulcherrima, ht 3.5 m) reminded me of the wide variety of members of the genus Euphorbia. It is a very large genus, with around 2,000 species, including annuals, herbaceous perennials, shrubs and cactus-like succulents. Because their 'flowers' are actually bracts surrounding much smaller true flowers, they last for a very long time in the garden. The poinsettia is probably the best-known member of the tribe that grows well in Sydney gardens, and its large, flame-coloured bracts are very welcome in June and July to brighten up the winter scene. I am particularly fond of it as my plant was a cutting from my childhood garden, and I enjoy that tangible link to my past. There is a double-red form that is also striking, with very long-lasting blooms, as well as single creamy-yellow and pink forms of the plant that are very attractive.

Euphorbia cotinifolia

Also on a shrubby scale is Euphorbia cotinifolia (ht 3 m), a wonderful plant with gorgeous burgundy leaves. Mine has lost almost all its foliage now but these will re-emerge spectacularly in late August to form an excellent backdrop in a border, flattering to almost any hue of flower grown nearby. Its own blooms are insignificant. It grows easily from a cutting and is one of my favourite shrubs in the garden.

Euphorbia Diamond Frost, right, at Government House, Sydney

A much smaller member of the genus is Euphorbia 'Diamond Frost', which grows to a 50cm cushion and is spangled almost all year round with tiny white flowers. It is a tough plant, coping with drought and heat, and flowering best in full sun. It can grow quite wide, so I occasionally chop it back hard to control its girth. It also self-seeds a bit, but I have never found it to be a problem.The species name of this one is a bit hard to pin down, but it may be Euphorbia hypericifolia. It is a great filler between other plants. I enjoy seeing it contrasted with very dark leaves (as illustrated here) but it is a suitable partner for almost any other plant in the garden.

Euphorbia characias subsp. wulfenii

The herbaceous Euphorbia specimens with their amazing lime-green bracts that are seen in many of the famous English gardens alas do not grow terribly well in Sydney, perhaps because, being of Mediterranean origin, they do not like our humid summers. They may last a few seasons, but then will often suddenly die off. I have had good success with Euphorbia characias subsp. wulfenii (ht 1 m) over the years, as long as it is grown in a sunny, well-drained situation. It has blue-green foliage and in late winter and early spring produces gorgeous heads of chartreuse bracts, which look stunning with blue or purple flowers growing nearby. It does eventually get a bit woody but usually a few seedling will have sown themselves nearby, so these can replace the original plant.

An annual Euphorbia - E. coralliodes (ht 60 cm) - gives the same wonderful colour and is easy - maybe all too easy - to grow, as it perpetuates itself by self-seeding from year to year. I pull most of these seedlings out but leave in just a few so that I can have those limey flowers in late winter and early spring. Another annual form - Euphorbia marginata (ht 60 cm) - which is sometimes called 'snow on the mountain', is one I hope to grow some time. It has white-variegated leaves and clusters of white bracts in summer, and I think it would be a great addition to my black-and-white border. It is a very adaptable plant, growing in cold as well as warm regions.

Euphorbia milii

Of the cacti-like succulent forms, one commonly seen species is Euphorbia milii (ht 1 m), often known as the 'crown of thorns'. It is very thorny and bears flat sprays of rounded bracts in colours including red and yellow. It is sometimes used as a low hedge.

All Euphorbia have a milky sap that can irritate the skin and cause temporary blindness if it gets in the eyes, so gloves should be worn when handling the plants and caution exercised.