"Diverse Euphorbia"

The huge genus Euphorbia has many varied forms!
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.

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.

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.

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.

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.

 Reader Comments

1/7  Lou - 2350 (Zone:8-9 - Cool Temperate to Alpine) Monday, 02 July 2012

Is Euphorbia "Diamond Frost" frost hardy? Sorry I didn"t mention that - it survives through winter in my garden, which gets an occasional frost, but in very frosty regions I gather it should be regarded as an annual. Deirdre

2/7  Peta - 2758 (Zone:9 - Cool Temperate) Monday, 02 July 2012

Amazing how one genus can have so many species suited to different climates. E. "Diamond Frost" was fabulous here at Bilpin "til the frost so I treat it as an annual. It"s like gypsophila, but easier. My favourite is the elegant Euphorbia characias "Silver Swan", variegated leaves and flowers. Thanks, Peta. In your cooler climate, many of the herbaceous ones like "Silver Swan" do much better than they do here in Sydney. I find they last a season or two then disappear. Deirdre

3/7  Robin - 2121 (Zone:10 - Warm Temperate) Monday, 02 July 2012

Please wear glasses or goggles when pruning any Euphorbia. The sap is projectile as I found out to the detriment of my eye! A very good point, Robin. Thanks for reminding us of that. Deirdre

4/7  Peter - 2008 (Zone:10 - Warm Temperate) Monday, 02 July 2012

I"ve found this other euphorbia being marketed at Darwin Wholesalers as E. geroldi "Patio Fire" to be an excellent short hedge to around 600mm tall & surprisingly shade tolerant Deirdre ... A wonderful genus I agree, one of the best :) Looks an interesting one, Peter; I love those rounded flowers. Deirdre

5/7  Margaret - 2067 (Zone:10 - Warm Temperate) Thursday, 05 July 2012

I have a good specimen of Euphorbia Cotinifolia which is getting far too tall. How hard can I cut it back. It can be cut back pretty hard. Maybe do it in late winter. Deirdre

6/7  Bronwyn - 4061 (Zone:10 - Warm Temperate) Thursday, 05 July 2012

My Poinsettia is one of those dwarfed specimems you see at christmastime which is too big for it"s pot. Should I repot or plant in the garden? Either would be OK. I think they are treated with something to make them stay dwarf but it might grow into a shrub if you put it in the garden. Deirdre

7/7  Anne - 2518 (Zone:10 - Warm Temperate) Saturday, 14 July 2012

Great blog - another good white shrub is Euphorbia leucocephala. I love Diamond Frost - it also layers itself but easily removed. Thanks, Anne. I"d like to grow E. leucocephala some day. I haven"t ever seen it in a nursery. Deirdre

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