With people you can often tell at a glance who’s related. Sometimes that’s also true of plants. Look at any daisy-shaped flower, for example – rudbeckia, coneflower, aster, sunflower, Shasta daisy, silphium – and you immediately know they’re in the same family. They’re all composites, members of the Compositae. Kissing cousins, as it were.
Not so with the poinsettia and its kin. Also known as a spurge, it and other members of the Euphorbiaceae family are as diverse as you could possibly imagine. Did you know that the white-flowering Diamond Frost that started adding sparkle to our gardens, especially our container plantings, about 10 years ago is in the Euphorbia genus? Euphorbia hypericifolia ‘Inneuphe’, to be precise. Big splashy red “petals” (modified leaves called bracts) on poinsettias. Teeny glilttering white blossoms on the Diamond Frost.
Then there’s the variegated native annual snow-on-the-mountain (Euphorbia marginata), which I’ve seen growing wild in pastures in western Kansas. I’ve grown it from seed here in Chicago, and it graces this issue’s cover with an appropriately frosty holiday look.
If you tour the great show gardens of England, you’re likely to see another amazing plant, Euphorbia wulfennii. This one looks like a 5-foot tall fluffy shrub topped with clusters of lime green flowers. Gardeners there use it as a complement that enhances the beauty of adjacent plants, but it’s so monumental it can also stand on its own as a “sculpture” or focal point. Pity it’s not hardy here.
Closer to home, you can find the unusual, prickly crown-of-thorns (E. milii) at many garden centers. Some of you may grow it as a houseplant. Its flowers are usually red, but there’s now a cultivar on the market with creamy yellow blooms marked with orange and green highlights on the petals and a bright orange center. The name: ‘Yellow Delight’.
And when I once visited South Africa, I saw tall succulent plants that looked like cacti. I would never have imagined that they were also euphorbias and related to our bright red poinsettias.
Nature is downright strange sometimes.
In spring a young man’s fancy supposedly turns to thoughts of love, but at holiday time, young men and the rest of us start thinking about poinsettias (Euphorbia pulcherrima). The breeders keep tweaking the colors, adding splashes and dappled dots and picotee edges along the way, but most of us are happy traditionalists who covet the brightest, richest red we can find. Put one anywhere in your home and it will immediately shout “Holiday!”
Here are some points worth keeping in mind when you go shopping for your poinsettia this year.
- Poinsettias get their English name from Joel Poinsett, America’s first minister to Mexico. An amateur botanist, he began sending samples of the plant home to the United States, and by 1836 it was already becoming known as the “poinsettia.” A modest beginning from which today’s monumental floral industry began.
- Poinsettias are not poisonous. Like all euphorbias, they exude a nasty-tasting milky sap that contains latex, but a study at Ohio State University showed that a 50-pound child would have to eat more than 500 leaves to become seriously ill. Even my cat, who nibbled on every poinsettia I brought home, quickly lost interest after he had taken a few bites. Enough to disfigure the plant but not enough to cause an upset tummy.
- Poinsettia flowers are not actually the big red (or pink or white) flappy things that we may think are petals. Those are actually modified leaves called bracts while the “real” flowers are the yellow clusters in the center, technically known as cyanthia.
- Care? Use common sense. Provide moderate light, which means no blazing sunlight and no shade. Keep soil lightly moist but not soaking. No drafts or temperature extremes. Don’t place it near a forced air furnace vent, for example.
- Also use common sense when taking your plant home from the store. Provide plenty of protection from the cold. A good garden center will wrap it in a paper cone, and surrounding it with an additional plastic bag is a good idea, too. Don’t leave it in a cold car while you go shopping elsewhere. Remember: Poinsettias originated in Mexico.
- Forget about trying to get your plant to rebloom. The process is cumbersome, and even if you remember to put your plant in a totally dark closet from 5 p.m. to 8 a.m. every night beginning at the end of September and continuing to December 15, the bracts will not turn the vibrant red that you desire. Let the greenhouse professionals do the work for you and relax. (However, if you’re a glutton for punishment, University of Illinois Extension has clear, succinct reblooming instructions. See bit.ly/1LspyKG.)
Poinsettias and most of the euphorbias we encounter are not hardy in Chicagoland, but there are some that we can grow with good results.
Euphorbia polychroma or cushion spurge is a compact mounding plant a foot or so in diameter with yellow flowers. It usually blooms in May. Sometimes, when the stars aligned just right, it would bloom in a garden around the corner from me as part of an attractive trio with a lily-shaped tulip and the orange-to-yellow native columbine, Aquilegia canadensis. If the weather didn’t cooperate, however, the three plants would bloom independently at three different times. Some horticulturists now call cushion spurge Euphorbia epithymoides, but I am sticking to the original name.
Worth seekling out is E. polychroma ‘Bonfire’. This new cultivar has yellow flowers that show off dramatically against dark burgundy foliage. To see it growing in Chicago, walk about the perennial garden on the east side of the Art Institute’s Modern Wing. You will recognize it by the telltale dark foliage that turns bright red in fall. E. polychroma and its cultivars are best grown in full sun although the one in my neighborhood did just fine in dappled shade. They are also tolerant of poor soils.
If you prefer orange flowers to yellow, try to get your hands on Euphorbia griffithii ‘Fireglow’, which grows up to 30 inches high. It’s not easy to find here, nor are we really sure of its hardiness. I had one that overwintered but succumbed later that year. However, I can attest that a cross of ‘Fireglow’ and ‘Bonfire’ has yielded a plant that is definitely hardy in Chicagoland – Euphorbia ‘Jessie’.
‘Jessie’ is the brainchild of Barry Glick, a plant breeder in Pennsylvania who announced its arrival with great fanfare on a list serve for garden writers a few years ago (sunfarm.com/specials/euphorbiajessie.php). It could survive super cold winters and 100 F. Texas summers, he said, and it was deer resistant. I ponied up and bought one.
I’m glad I took the bait. The plant that arrived was small and spindly, it grew half-heartedly that first summer, and my expectations for its winter survival were dim. But lo and behold, as soon as it poked its nose through the ground the following spring, it was off and running. It grew tall – 2, then 3 feet – but didn’t bloom in my semi-shady site, so after three years, I moved it to full sun. Bingo. It soared 4 feet high or more, and the flowers looked just like those on Glick’s website. This year, it was one of the earliest perennials to break dormancy and I currently have around 15 tall stems. Since the soil in Hyde Park has a sandy base, a few plants in my garden need additional support. This year I provided ‘Jessie’ with a nice round tomato cage to keep all of the stems pointed in the right direction.
I still find it hard to believe that the stately, towering ‘Jessie’, the twinkling Diamond Frost and the spiky crown of thorns are all relatives of poinsettia, but it’s true. And that’s just for starters. The Euphorbia genus actually includes more than 2,000 members, ranging from tiny annuals to large and long-lived trees, which makes it one of the largest genera of flowering plants anywhere.
Whether this makes the euphorbias one big happy family, I can’t say. But for those of you who like to pluck life lessons from nature, here’s one. In nature as in real life, you can’t choose your relatives.
Editor Carolyn Ulrich has written for Chicagoland Gardening since its inception. She is a former weekly garden columnist for the Chicago Sun-Times and has received several awards for magazine writing from the Garden Writers Association. firstname.lastname@example.org
- Cushion spurge (E. polychroma)
- Cushion spurge (E. polychroma ‘Bonfire’)
- E. griffithii ‘Fireglow’ (maybe hardy)
- E. ‘Jessie’–cross of polychroma and griffithii
- Poinsettia (E. pulcherrima)
- Crown of thorns (E. milii)
- Snow on the Mountain (E. marginata)
- Diamond Frost (E. hypericifolia ‘Inneuphe’)
- Euphorbia wulfennii