A long-standing horticultural mystery finally solved!

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Although common enough in culture, burro’s tail (Sedum morganianum) was long at the center of a horticultural mystery.

A 70-year old horticultural mystery was recently solved, one I’d thought a lot about over the years. You see, I’ve been growing burro’s tail, aka donkey’s tail (Sedum morganianum) for almost 40 years and remember reading in a magazine article ages ago that its origin was a mystery, that it had never been found in the wild. It just seemed so strange to me that a plant of unknown origin could be so widely available. After all, you’ll find burro’s tail in just every garden center.

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Photo of hanging baskets of Sedum morganianum taken by Eric Walther at the nursery where it was found in 1935. Photo: http://www.crassulaceae.com

The trailing succulent with long pendulous stems covered with pale blue-green leaves has in fact been cultivated since at least 1935, when American botanist Eric Walther found it growing by the dozens in hanging baskets in Jardín Flottante, a small nursery in the town of Coatepec, in the center of the state of Veracruz, Mexico. He brought it back to California where his friend, Dr. Meredith Morgan, managed to get it to bloom, a necessary step in its identification, as Walther was, until then, unsure whether the plant was a sedum or an echeveria (Echeveria), but the details of the flower revealed its true identity. When Walther officially described it in 1938, he named it for Morgan… and the botanical description bore the inscription ”type locality unknown”.

Multiple Searches

Since 1935, Veracruz has been visited by many botanists, all of whom have hoped to solve the mystery, which is very well-known in botanical circles. As they looked, the different botanists made plenty of other discoveries, including more than 40 other new species endemic to the state of Veracruz, but none of them found S. morganianum.

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Sedum morganianum growing in the wild in Mayatla canyon.

In 2008, however, Mexican botanists David Jimeno-Sevilla and Amparo Alvalat-Botana, under the supervision of Miguel Cházaro, who had himself searched in vain for the plant in the wild over many years, were carrying out floristic studies in Tenampa, Veracruz, some 50 km south of Coatepec. They ran into Carlos Ros, the owner of the ranch where they were working, Rancho Bellreguard de Sochiapa, and he said he had seen the plant on his property about 2 months previously. And it turned out to be true! He was able to show them the plant in situ, on vertical cliffs of igneous rock in two different ravines, Mayatla and Ixcacotitla. Seeing the plant was one thing; climbing up after it, quite another, but they were nevertheless able to bring specimens back to Universidad Verzcruzana where the plant’s identity was confirmed.

Popular

Its mysterious origin didn’t prevent the burro’s tail (from the Spanish “cola de burro”) from becoming popular. By the 1950s, barely 10 years after it was described, it was being commonly grown throughout the New World as well as in Europe and Australia.

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A single leaf deposited in a pot will produce a new plant.

This is almost certainly because it is so easy to share: all you need is a single leaf to start a new plant. Just drop it into on a pot of growing mix and it will (slowly) produce roots and then a stem and leaves, forming a new plant.

It actually turns out that this method of reproduction is the one that it most often uses in the wild as well. A leaf is knocked from its stem by the wind or an animal becomes lodged in a crevasse… and there you go: a new plant is born!

In tropical countries, notably ones with arid climates, burro’s tail is widely used as an outdoor plant and can be seen dripping from hanging baskets everywhere. In temperate regions, it’s grown as a houseplant in hanging baskets or wall pots. It’s a tough plant that grows well even when thoroughly neglected.

Like all sedums, burro’s tail prefers full sun, but will tolerate more moderate light, such as an east window.

It’s adaptable when it comes to potting soil and any mix, whether rich or poor, alkaline or acid, will be suitable, provided it drains well. It does like to its soil to dry out a bit before you water it again, especially during the winter, when it’s subject to rot under the deadly combination of short winter days and soggy soil.

It’s extremely tolerant of summer heat, but not winter cold and will tolerate no frost whatsoever. Aim for a minimum temperature of 55˚F (13˚C).

Burro’s tail grows slowly even under the best conditions and doesn’t require much fertilizer. In fact, even if you never fertilize it, it will still grow perfectly well.

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Sedum morganianum in bloom

Burro’s tail only blooms sporadically when grown indoors, although it may bloom annually when it’s outdoors in the tropics where the sun is more intense. At any rate, the purplish pink star-shaped flowers are less attractive than the plant’s overall appearance, what with its long trailing stems (they can exceed 3 feet/1 m in length!) covered with pointed succulent leaves that take on an attractive pale blue-green coloration because of the bloom (whitish wax) that covers them. Most gardeners don’t much mind if their burro’s tails never bloom!

You’re not going to want to move your plant around much, since it loses leaves at the slightest touch. Hang it up somewhere you or guests are not likely to bump into it, or that will leave a shower of fallen leaves on the floor and sections of bare stem in the plant. This is one of the rare succulent houseplants that I don’t put outside for the summer: moving it indoors and out simply causes too much damage.

When your plant has lost too many leaves, it will be less attractive. At this point, it’s best to start a new plant from leaf or stem cuttings. Since transplanting this plant is likely to damage it, may I suggest you start your new plants directly in the hanging basket or wall pot in which you’ll be displaying it. About 10 or so leaves dropped on the potting mix will create a nicely full plant… many months later (it remains a very slow grower).

Two Imposters

There are two other plants that can easily be mistaken for S. morganianum: S. burrito and X Sedeveria ‘Harry Butterfield’ (as well as other X Sedeveria varieties).

Sedum burrito

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Sedum burrito

S. burrito is often called baby burro’s tail or baby donkey’s tail, although the plant is not really any smaller, it’s just that it’s leaves that are shorter.

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S. burrito stems (note the rice grain-shaped leaves) with one stem of Sedum morganianum (in the red rectangle) with banana-shaped leaves. 

This plant looks so much like S. morganianum that many people confuse the two. In fact, in the trade you often you see a mixture of the two in the same pot as in the photo above! Both plants have an identical growth habit, with the same pendent stems, plus the same purplish pink flowers, but S. burrito’s shorter leaves are bluer in color, borne more horizontally and densely and have a rounded tip rather than pointed tip of S. morganianum. Think of it this way: if the leaves are shaped like a grain of rice, you’re looking at baby burro’s tail (S. burrito); if they look like little bananas, it’s a burro’s tail (S. morganianum). When you see the plants side by side, as in the photo above, they actually look quite distinct.

I also find S. burrito better holds onto to its leaves when you move it, though it will drop them if given a hard enough knock.

Oddly enough, S. burrito has a similar history to S. morganianum. It was also discovered, not in the wild, but in a nursery in the town of Coatepec, but four decades later. That’s where botanist Reid Moran spotted it in 1975 before bringing the plant back to the United States from where it too conquered the world.

To this day its location in the wild remains unknown… and again it is presumed that it’s growing somewhere on a cliff in the state of Vercruz. So if you’re ever interested in a bit of plant exploration…

S. burrito has been officially described as a species, but many botanists feel it would be best described as a variety of S. morganianum: S. morganianum burrito.

X Sedeveria

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X Sedeveria ‘Harry Butterfield’ has much longer leaves than S. morganianum.

Another plant you could confuse with S. morganianum is the intergeneric hybrid (i.e. a cross between plants of two different genera), X Sedeveria ‘Harry Butterfield’ (and similar hybrids). It comes from a cross between S. morganianum and Echeveria derenbergii and is usually called, for good reason, giant burro’s tail, for its succulent leaves are distinctly longer than those of S. morganianum. Other differences are its shorter stems (they rarely reach more than 20 inches/50 cm in length) and its yellowish to orange flowers compared to S. morganianum’s purplish pink blooms. Its leaves, on the other hand, are just as fragile as those of S. morganianum and therefore the plant should be handled with care.

You can multiply both “imposters” just like S. morganianum, by leaf or stem cuttings.


And there you go: one plant mystery is solved, one remains intact… and there are now three very attractive hanging succulents you might want to grow in your home!20170217a

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