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Plant Profiles

The Best Season Ever: Acidanthera



In August or September, acidanthera finally surprises me by starting into bloom. I say "finally," because I've been awaiting the flowers all Summer. Gladiolus murielae always takes its time, but it's nothing if not reliable. But flowering is still a surprise because the nodding sprays of buds don't top the foliage, and are so leafy in color and form that they often escape notice until, one day, seemingly from nowhere, large and fragrant flowers are out.


Pure white tepals are blotched with burgundy at their bases. The three yellow stamens are large, indeed, but the white-and-burgundy coloring of the tepals is so vivid that you see the stamens only on second glance.




Still closer, the three-armed style that receives pollen. It's more deeply held than the comparatively enormous pollen-bearing stamens. Nectar glands are deeper still, so pollinators can't help but brush by the style as they forage. Only at this close range are the pink dots visible. They extend deeper coloring farther up into the bright white but, overall, the flowers read as just burgundy and white.




The green of the buds and the stems that bear them is identical to that of the foliage. You only realize that flowering is imminent if you notice that the foliage tips are vertical, and the bud stems are nodding.




I keep a large colony of acidanthera in a nursery pot year-round. (Acidanthera corms are usually lifted and stored warm and dry, free of any soil or packing material. See "How to handle it," below.) Only when you've gotten the nodding shape of bud stalks in your head do you begin to see them amid a colony's profuse and erect foliage. Outer leaves may curve broadly along their entire length, but bud stems are erect until their top ten inches or so, when they might bend ninety degrees and more.



Here's how to grow this easy corm:

Latin Name

Gladiolus murielae, also known as Acidanthera callianthus, Gladiolus callianthus, and Gladiolus callianthus 'Murielae'

Common Name

Acidanthera, peacock orchid, Abyssinian gladiolus, sword lily, fragrant gladiolus.


Iridaceae, the Iris family.

What kind of plant is it?

Corm-forming herbaceous perennial.


Zones 7 - 10. 


Tight clusters of vertical sword-like foliage from fast-growing (and multiplying) corms, creating clumps of growth dense enough to serve as groundcover. Late in the season, graceful nodding flower spikes emerge. They are the same green as the leaves and, while just in bud, are so narrow that they are easy to miss. The foliage tips remain erect (although the entire fans of growth in a clump are often forced to lean outward), so the first hint that flowering will begin soon is one of texture or geometry: All of a sudden, the tips of just a few of the "leaves" seem to have started to droop.

Rate of Growth

Slow until July, then fast.

Size in three months

Gladiolus murielae is always planted in groups; like others in the genus, it looks artificial growing as a soloist, when it could seem like a cut flower stuck in the ground foliage and all. A group of, say, seven could form a clump eighteen inches wide at soil level, and two to three feet wide at the top. Overall colony height can be dependent on soil fertility and the availability of soil moisture. My colony topped out at about three feet above the soil level, which is probably the maximum. In leaner circumstances (and, probably, in the wild), colonies are closer to two feet tall.


Typically glad-like, with many upright fans of leaves in a dense clump. The nodding spikes of flowers, however, bring a casual irregularity that is a welcome contrast to the foliage's insistent verticality. Acidanthera is the glad for people who hate glads on account of their vertical (and, usually, in need of staking) flower spikes.

Grown for

its flowers: Flowers of Gladiolus murielae are white with striking burgundy throats. The tips of the petals can be light pink, and there are pink dots above the splashes of burgundy, but these are visible only at close range. From any distance, the burgundy-and-white coloring is a little binary: either bright white or deep and dark. Acidanthera flowers aren't, in themselves, essays in subtlety, but they are displayed with grace. Instead of the vertical spires of cheek-by-jowl flowers that are typical of florists' glads, acidan- thera flowers are few and well-spaced along a short arching stalk. Further, they are rarely held higher than the foliage but, instead, seem to be dancing amid the top layer of it. 


Perhaps even more notable: The flowers are deliciously fragrant, an extremely rare talent for any glad. Sweet and, on a warm still day, surprisingly penetrating, the scent is a surprise late in the season, when most flowers are advertising themselves with color and profusion (think mums, daisies, hydrangeas, and dahlias).


its ease of cultivation: Corms are easy to overwinter, reproduce like rabbits and, as long as you plant in sun when the soil and weather are warm—and (true) your growing season isn't too short—flowering is nearly fool-proof.

Flowering season

Flowering usually begins in August (but some years not until September) and continues until frost.

Color combinations

The burgundy-and-white flowers are striking in form, size, season, and pattern of pigmentation; surrounding colors are best restricted to burgundy and white. You might also add pink or rose, which will call out to their modest presence in the flowers. But that's it. See "Plant partners."

Plant partners

Acidanthera's slow early season, strongly-vertical foliage mid-season and, finally, late-season flowering each provide challenges and opportunities for helpful and even exciting neighboring plants.


Early Season: For some weeks after planting, a colony of acidanthera looks like nothing but a patch of bare dirt, as the just-planted corms develop roots and only begin to send up the tight fan of foliage. And yet, if the soil surface is covered over with distractingly full and attractive companion plants—even those that the emerging foliage spikes can easily pierce—the acidanthera's progress can be delayed or even stopped by the cooling effect of the companion plant's shade on the soil into which the corms are planted. Further, because acidanthera needs a long season to flower even under the best circumstances, corms can't be poked into the ground as a follow-on to Spring ephemerals such as bulbs, oriental poppies, or dicentra. Lastly, if uninterrupted fullness of display is your goal, you'll need to delay placing pots of acidanthera in their intended locations until after their foliage is up. This could be June unless you've started your containers of acidanthera indoors. 


For my money, the best plant partners for acidanthera before, oh, mid-June would be colonies of tulips that were planted very deeply. They would be the placeholder for acidanthera that you start in plastic bulb pots, which are those six-inch-wide plastic pots that are broader than they are tall. After the tulips have died back, carefully dig through the top six inches of the soil above their bulbs, to prepare it to receive carefully-unpotted clumps of acidanthera. See below, "How to handle it: Another option—or two!"


Mid-Season: There can be two or even three months of vigorous foliage growth before flowers begin appearing in August or September, making acidanthera a foliage plant from late Spring until high Summer, not a flowering one. Moreover, the solid green leaves can only provide coloristic excitement if their surroundings are either variegated or another color entirely. But the emergence of the lively white-and-burgundy flowers—which, in their own way, read as strongly variegated—would probably clash with any variegated partner plants. 


Thus, the options for companion plants that maintain their interest through the Summer are for leaves solidly pigmented in one of the few colors compatible with the acidanthera flowers (burgundy or white), a leaf shape (ferny or rounded or palmate) that is, in itself, a lively difference from the acidanthera's swords, and a habit (dense and low, either mounding or cascading) that places a broad and graceful base near or around the dense vertical sheaf of acidanthera foliage.


Burgundy-leaved forms of sweet potato would be fool-proof. Leaves of Ipomoea batatas 'Sweetheart Purple' are cordate (heart-shaped); those of 'Sweet Caroline Bewitched' have only a few short pointed lobes; those of 'Blackie' have feathery narrow lobes reminiscent of those of a cut-leaf Japanese maple. Another option would be white-flowered forms of Bacopa. The big exception to low companions is Verbena bonariensis, which is as strongly vertical as acidanthera. But in every other detail, it is gloriously acidanthera-antithetical: Pencil-thin stems in see-through clusters, leaves that are sparse as well as tiny, and pointillistic heads of minute lavender flowers.  


Late Season: Because the floral show of acidanthera often extends to the arrival of frost, companion plants that flag by September would be detracting. And because foliage of acidanthera changes only in bulk and height over the Summer, not in color or texture, companions that don't begin to provide much interest until the acidanthera flowering season won't be much help during the glad's foliage-only months. The only hardy plants likely to be able to provide the lengthy and sustained peak performance through color would be purple-leaved shrubs such as Weigela florida 'My Monet' at the front or Physocarpus opulifolius 'Summer Wine' or Cotinus 'Velvet Cloak' at the back. And through texture? Perhaps Amsonia hubrichtii. Tropicals and annuals, such as the sweet potatoes, verbena, and bacopa above, will more easily provide a quality show from late Spring through hard frost. Just as important, they are also slow out of the gate through early Summer and, so, could be more closely combined with acidanthera without the danger of shading its planting area or its emerging foliage.


If I were blessed with the opportunity to execute what the British call a warm-weather "bedding scheme"—meaning, a bed whose plants are changed seasonally—I'd do a Summer-to-frost matrix of just Ipomoea 'Blackie,' Verbena bonariensis, and Gladiolus murielae, whereby each plant is as likely to appear in the interior of the planting as at the perimeter. Because 'Blackie' can creep around and through anything, and Verbena bonariensis is see-through even when at its fullest, the the results would be a three-dimensional tapestry, first, of textures and shapes (erect swords of acidanthera, prostrate hearts of 'Blackie', and vertical shimmer of the verbena) and, only second, of color (the burgundy of 'Blackie' leaves matches that of acidanthera's flowers, and contrasts beautifully with its foliage; the lavender heads of verbena flowers go with everything). Check here to determine whether Verbena bonariensis is considered invasive where you are gardening. 

Where to use it in your garden

Acidanthera succeeds in containers as well as in the ground.  Whereas the challenge with florists' glads is quickness to flower (which you can finesse by planting additional corms every couple of weeks so as to extend the overall period of bloom), the challenge with acidanthera is the lateness of flowering. You can't solve this by planting in the garden extra-early in the Spring, either: In cold wet soil, the corms are as likely to rot as to sprout.  In a climate with a short growing season, or if you simply want to encourage earlier flowering, you can start corms indoors in a container, which you bring outside only after the weather is solidly warm. 


Wherever you site acidanthera, maximize not just the sun that reaches these corms' foliage, but also that which reaches the surface of the soil where the corms are planted. Only in climates that are hot, and whose growing season is long, would it be possible to plant acidanthera in a bed where near neighbors cast shade onto the soil surface, even if not onto the foliage. Instead, site corms where any neighboring plants (especially to the south and west) are low enough or far away enough that they don't shade the soil in which you've planted the corms. Happily, this doesn't always mean that you need to plant corms in the middle of a large and otherwise bare stretch of ground. See "Plant partners," below, for strategies.


Planting the corms in a large container that you set where it as well as the acidanthera's foliage both receive plenty of sun is usually the easiest way to ensure warm soil, a quick start of growth, and a timely flowering season. Companion plants should be low, especially those at the south and west. Even better, grow the companions in separate containers that you set only close enough that the pairing with the container of acidanthera is established, but not so close that they shade the acidanthera's container. See "How to handle it: Another option—or two!" for more details. 


As long as you keep these cultural provisos in mind, a clump of acidanthera can be an easy and dramatic vertical accent. You could even emphasize a clump's upward thrust by planting in a tall container; these are now fashionable, and there will be many choices. Handily, that added height also ensures that the clump's foliage and soil mass experience maximum sun and heat. A series of such "high hat" containers of acidanthera could be spaced at the side of a sunny walkway, or could punctuate the corners of a rectangular terrace or (if you really have plenty of containers) the perimeter of a curved one. When in full flower in September, such a stretch of paving would be as powerful an olfactory experience as a visual one. 


Just remember that acidanthera clumps seem to be nothing but bare dirt for several weeks after planting. Yet another advantage of planting them in containers is that you can keep the containers in a sunny but out-of-the-way spot until new growth is nicely evident. Then place them center stage.


Full sun and rich but well-draining soil. Plant full-sized corms 5-6" deep; plant smaller ones 2-3" deep. If you plant corms 4" apart, the growth within the clump will be so tight as to act as a groundcover.

How to handle it: The Basics.

When growing directly in the garden, plant corms in Spring only after the soil has warmed and the sun is strong. If the weather isn't mild enough to set out tomatoes, it isn't yet warm enough to plant acidanthera. Although acidanthera doesn't appreciate poor drainage, it is more vigorous when not stressed by drought: Water weekly after the dog days arrive. After a few frosts have completely killed back the foliage, dig up the clumps. Gather the much-smaller daughter corms—known as cormels—so you'll have even more to plant next Spring. Cut off the foliage and allow the surface of the corms to dry fully in a warm, dry, and sunny location. Then bag up the corms and store them warm and dry for the Winter. It's fine to place them in a dark spot such as a closet or the attic. I use a large brown paper bag to hold my acidanthera corms, but if you have burlap bags, even better: Air flow is always helpful in keeping the corms dry and fungus-free. 

How to handle: Another option—or two!

Gladiolus murielae is very happy in containers. In the shortest term, you'd be starting pots of corms in early Spring so that your acidanthera clumps have an earlier foliage presence in late Spring, and (we hope) and earlier start to flowering. Corms might be in such containers for just six or eight weeks, so plant the corms tightly, and just in shallow containers known as bulb pots. After mild weather has truly arrived, dig up the intended garden location and, since the corms are growing so tightly, enrich it with compost. Prepare the planting hole itself before you unpot the acidanthera; make it two or three inches deeper than the height of the pot, so that there's plenty of room atop the unpotted root mass for additional soil. When acidanthera is planted deeply—with soil at least five inches atop the bulbs—the stems are particularly stable, and less likely to tilt after windy weather. So go ahead and add loose topsoil between and even on top of the emerging spears of acidanthera foliage, which will soon lengthen and reach the surface.  


Medium-term, you can grow acidanthera in a container for the entire season. To have five or even six inches of soil atop the corms and a similar depth of soil beneath them, you'll be choosing a container that is deep as well as somewhat large. The size of a three or even five-gallon black nursery pot would be the minimum. (In the pictures above, I've planted a couple of dozen corms in a ten-gallon pot.) Plant a minimum of three full-sized corms in a three-gallon-sized pot. Water once after planting so that the corms begin absorbing moisture and growing. Set the container where it receives plenty of sun, so that growth starts quickly, and progresses eagerly. After spears of foliage are four inches and higher, move the container into its "display" position. Water as needed; by August, this could be every other day. Fertilize weekly. After frost has killed the foliage back—but before cold is so sustained or intense that the pot's soil freezes—empty the pot and retrieve the corms. Store as above.


For the true long-term, you could grow acidanthera in a container permanently. Begin as above, but bring the pot into shelter, without disturbing the corms, after flowering has slowed or stopped but before the foliage is frosted. As the plants achieve dormancy, the foliage will pull moisture up out of the soil while the corms' roots will have pulled more of it from the soil into the corms. The result will be soil dry enough to act as the storage medium for the Winter. Leave the corms planted in the container, and set it in a warm and dry place for the Winter. If you have the space to bring the container into a warm and sunny location in late Winter or early Spring, do so. Water deeply once; wait until new spears of foliage are visible before watering again. Set the container outside only after the weather is warm, and grow as above.

Quirks and special cases

Although acidanthera can be hardy even into the mildest portions of Zone 6, especially if planted more deeply and heavily mulched, there's little to be gained by letting the corms remain in the ground year-round. Even in milder climates, growth is thought to be quicker and more vigorous if the corms are lifted and overwintered warm and dry. They store so easily there's little inconvenience. Plus, digging up and replanting the corms gives you the opportunity to share them with friends.


In my experience, the foliage isn't touched by the smaller browsers: rabbits, groundhogs, raccoons, and possums. Because my garden is fenced, I can't vouch for resistance to deer. The corms can be eaten by tunnelers such as voles and moles and, I guess, groundhogs if one of the tunnels of their den runs through a colony.


Corm edibility is thought to be one reason that production of the cormels is prolific. Tunnelers are likely to be so attracted to the full-sized corms that they'll ignore the cormels, so the colony can survive even when all the big corms are all eaten. In this sense, a clump of acidanthera enjoys the same herd immunity as gazelles do on the Serengeti: In both cases, predators can only "harvest" so many of the crowd of individuals, leaving enough to keep the population steady. 


I'm not aware of any other forms of acidanthera than the species itself. Despite being grown by the millions, no forms of acidanthera that are sufficiently different to merit a cultivar status have been introduced. This could be as much from the appeal of the species, as well as as its ease of propagation and use year after year: There just isn't financial incentive to bring cultivars to the market.


On-line as well as at retailers.


Easy! First, collect the profuse daughter corms—known as cormels—as you dig up the mother clumps for overwintering. Second, when you replant in the Spring, pull apart the clumps of mature corms into individuals, discarding any that have clearly expired or decayed, and plant them along with the cormels. Because a single corm can mature into a clump of corms and cormels in one season, in just a few years you might have several cubic feet of corms: Far more than you might ever want. I was introduced to acidanthera by an elderly woman who, apparently, had believed that More was More for the long-term. She brought down from her attic several bushels of corms and gave me half a grocery bag of them.


Because Gladiolius murielae is available only as the species, not a cultivar, seeds will come true, too. But the corms are inexpensive to buy, easy to overwinter and—as above—almost too eager to propagate, so there's little to be gained by going to the trouble of growing from seed.

Native habitat

Gladiolus murielae is native to mountainous areas in east Africa from Ethiopia to Mozambique.

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