by Arthur (Art) G. Guppy
Scoliopus is a genus seldom seen in alpine gardens, which is strange, as either of its two species is easy to grow and both are of unusual interest. Scoliopus hallii has rather small, almost inconspicuous flowers, but they are of great interest for those who are willing to get down on their knees for a closer look. In contrast, Scoliopus bigelovii, although its flowers are not much more colourful than those of its close relative, makes up for that deficiency by having larger flowers and a great many of them, and at a time of year — late winter — when the garden begs for flowers.
Not only have alpine gardeners not given the deserved amount of attention to Scoliopus, but it is obvious from the inadequate and often inaccurate treatment of the two species in published floras that botanists have been equally neglectful of two extremely interesting plants.
The range of Scoliopus hallii is limited to western Oregon, where it is mainly to be found on stream banks in mixed coniferous-deciduous forest. That tells you it likes a fairly consistent supply of moisture, at least through the spring months, but it is not a bog plant. It likes shade, but prefers to be under deciduous trees or shrubs that allow it some glimmers of sun in early spring. In its natural habitat I have seen it in bloom in February, but in my garden on southern Vancouver Island it generally blooms in March and early April. It can withstand summer dryness provided the dryness does not come too early in the season.
Scoliopus bigelovii has a natural range confined to the San Francisco Bay area and the North Coast Ranges of California. I have not seen it in the wild, but apparently it is a plant of hillside seepage areas in cool redwood forests up to about 1100 metres altitude. In my northern garden it requires much less moisture than it gets in its natural habitat and likes a fairly well-drained site in deciduous shade where it is safe from dry conditions until mid-summer. Then it seems to appreciate a summer rest. It is likely that in its Californian home the spring seepage has dried up by summer. It has a long blooming period, and even in my northern garden generally has its first flowers open by mid-February. That means the leaves which sheath the emerging blooms often poke above the surface of the soil before the end of January, and they can pay for their eagerness by being badly damaged by a severe frost. Brown, frost-damaged leaf tips do not improve the appearance of the display of bloom in February and March, though moderate frosts at night during those months do no further harm. I learned the hard way to grow the species where it is sheltered from cold winter winds, and during cold snaps to put conifer branches over the plants.
Both Scoliopus species, especially the one from California, have a reputation for having foul-smelling flowers. Don’t let that discourage you from growing them. I have made a practice of inviting guests to sniff the flowers of S. bigelovii and describe what they smell. Most say they can detect no odour whatever, and no one has described the scent as being foul. I find that under ideal conditions, with my nose close among the flowers, I can detect a slight acrid scent. With S. hallii I have been able to detect no scent whatever. In one delightful old book, The Wild Flowers of California by Mary Elizabeth Parsons (my copy, among the “tenth thousand”, is dated 1909), there is a truly vivid description of the flowers of S. bigelovii: “These flowers are elegant in appearance, and suggestive of orchids; but unfortunately they have a very offensive odor, like that of the star-fishes found upon our beaches, which makes us quite content to leave them ungathered.” Perhaps the species would not be a good choice for a warm Californian garden, but in northern latitudes one can safely enjoy the fine display of long-lasting blooms without the slightest problem with odour.
Both Scoliopus species have mottled leaves, but with S. hallii the mottling is usually no more than a few randomly scattered purple spots or rarely the leaves may be plain green. The leaves are arranged in pairs, rather like those of Erythronium, but with old plants there are so many pairs pressed together they simply form a clump of leaves. (Strictly speaking, according to F.H. Utech 1992, the leaves have a spiral arrangement.) Unlike Erythronium, which has one erect stem (or a few with E. multiscapoideum), Scoliopus plants have many rather lax stems, each bearing a single flower. (Strictly speaking the flowers are on pedicels from a short underground peduncle.) These stems (or pedicels) continue to elongate after the flowers open and after they fade, so the developing capsules droop to the ground and sometimes are pushed along among the dead leaves and debris on the ground. From that behaviour of the capsules the plants gained the delightful common name slinkpod.
Scoliopus flowers are thoroughly unique. With the rather inconspicuous flowers of S. hallii and the more showy flowers of S. bigelovii, the purple-striped petal-like structures are actually sepals, and the real petals are narrow, upright shafts between the sepals. Unlike most members of the lily family, Scoliopus has flowers with only three stamens, though the upright anthers have a copious supply of pollen.
The plants grow from a short, firm rhizome with an extensive network of strong roots, which seems to be the main reason the genus is often said to be related to Trillium. This idea of a close relationship to Trillium is constantly repeated in the literature and often seems motivated by an attempt to split the traditional large, diverse lily family into several smaller families among which the splitter does not want Scoliopus to be by itself as a family with only two species. Consequently, we find Scoliopus placed with Trillium and Paris in the Trilliaceae. That linkage simply does not work as Scoliopus has too few similarities to Trillium and Paris and too many conspicuous differences from them. I will come back to this problem later, as the mistaken idea crops up so frequently in the literature I feel it needs to be eradicated.
The most interesting and unusual traits of this unusual genus are what I am calling its “secret lives”, that is, those aspects of the plants’ lives that only a very careful observer would notice, and which are not in any of the published floras that cover Oregon and California, but which I feel are as important as the physical traits of leaves, stems, and flowers. Recently I had the opportunity to look at Volume 26 (Liliales and Orchidales) of the recently published Flora of North America North of Mexico, only to find that, like other floras, it omitted the facts which I consider so very important. About the same time I obtained a copy of a paper on the “Biology of Scoliopus” by Frederick H. Utech (1992), who is also the author of the entry in Flora of North America, and there I found the two basic facts of the plants’ “secret lives” fully explained just as I had observed them. Evidently the information is omitted from floras as not being sufficiently important to be allowed to take up space. As I do not agree, I will here describe exactly what I have observed, and will go on to describe a third characteristic which it seems no one else has noticed, and which could well be the most important of all. The failure of authors to notice it has resulted in two floras, including the Flora of North America, containing a serious error.
After I had started growing the two Scoliopus species and had seen S. hallii in the wild, I understood they were unusual plants, but it was only after I had spent hours closely observing them in my garden that I realized how unique and fascinating they really are. Although I could detect little or no odour from the flowers, I was willing to accept the word of others that in their natural homeland they had a “fetid” or “carrion-like” odour (Hitchcock et al. 1969) or perhaps even the stench of a beached starfish in the sun, but those descriptions led me to expect the flowers would attract large blowflies such as are attracted to decaying meat. I saw nothing like that, and the flowers bloomed in such cool weather it was unlikely such flies would be active. Instead I observed an assortment of tiny flies that gathered around the flowers even when the temperature was not far above freezing. I had no idea of the identity of these tiny creatures until I sent a photo of one to my son, who is an entomologist. His specialty is Lepidoptera but he was able to tell me the photo showed a fungus gnat (tiny flies, sometimes mosquito-like, the larvae of which commonly feed on fungi). Later I obtained the paper by F. H. Utech and learned that fungus gnats are the usual pollinators of Scoliopus flowers even in their much warmer natural habitat.
Close observation of Scoliopus flowers of both species showed me that the petal-like sepals have on their upper surface toward the base an area that secretes a generous quantity of what I will call “nectar”, though it is obviously not the sugary substance produced by flowers that attract bees. It would be an interesting project for someone to determine what is in Scoliopus nectar that is so attractive to fungus gnats. Certainly it is these gnats that are the normal pollinators of the flowers of both Scoliopus species, and almost certainly the survival of the genus depends on these tiny insects. If one does not mind lying on the cold ground on a cool day with a magnifying glass, one can observe gnats obtaining nectar and in the process becoming dusted with pollen from anthers positioned above the bases of the sepals. One of the three stylar arms extends over each anther, and each arm has a small stigmatic area on the tip positioned to pick up pollen from incoming gnats.
When my first S. bigelovii plant had been flowering for a number of years and had produced no seeds, I began to suspect it was self-sterile. I needed another plant of the species, and eventually succeeded in obtaining seed and raising a few plants to flowering size. As soon as one flowered, I carefully removed its anthers and rubbed their pollen onto the flowers on one side of the old plant, while leaving the flowers on the other side untouched. The experiment was elegantly successful as a number of seed capsules formed on the pollinated side of the plant and absolutely none on the other side. Clearly S. bigelovii is self-incompatible and anyone growing these wonderful plants should have more than one if he or she hopes to harvest seeds. I could not easily test S. hallii for being self-incompatible, as I have several plants of the species growing close together and a plentiful exchange of pollen between them would be assured. One can readily see that the traits of being self-incompatible, of flowering early in the year, and of having an unusual pollinator ideally go together, for the first trait demands that pollen come from other plants of the same species, and the last two traits help prevent the useless exchange of pollen with unrelated species.
A second very important characteristic of the “secret lives” of Scoliopus is the adaptation of both species for myrmecochory, which is the dispersal of seeds by ants. These little creatures are so active that many plants have evolved ways of making use of ant-energy to disperse their seeds to growing sites where the new plants will not compete with their parents. Seeds of such plants generally have a fleshy appendage known as an elaiosome, which contains a volatile, scented substance highly attractive to ants which triggers their instinct to carry the object producing the scent to their nests. Presumably at the nest the elaiosome is consumed and the seed carried away from the nest to be discarded. Then there is a reasonably good chance the seed will be left where conditions are suitable for it to germinate and grow into a mature plant.
The first time I handled a Scoliopus seed I immediately noticed it had an elaiosome, and I became even more interested in the genus. I knew that now I would not only be down on my knees watching gnats, but a little later in the year I would be watching ants. There are at least two other genera in the lily family that are myrmecochorous, and the best known of these is Trillium. Obviously one could jump to the conclusion that the sharing of this trait by the two genera would be a good argument for including Scoliopus in the Trilliaceae. That argument breaks down because we also encounter myrmecochory in the genus Erythronium, which shares with Scoliopus an extremely similar pattern of seed germination (which I will describe later).
In view of that similarity and important conclusions we can draw from it, I must digress here to write a little about Erythronium. With the exception of one very unusual species, E. propullans, which normally does not produce seeds, I have tested with ants in my garden the fresh seeds of all the Erythronium species of Europe, Asia, and eastern North America, and with all those species the ants reacted by eagerly seizing the seeds and carrying them away. E. propullans is known to be closely related to E. albidum which is certainly myrmecochorous, so if E. propullans ever produces seeds they can be expected to have elaiosomes. The result of all my testing is that I can say with confidence that all the known Erythronium species of Europe, Asia, and eastern North America are myrmecochorous. I have inspected seeds of all the generally recognized Erythronium species of western North America and none have elaiosomes, and therefore none are myrmecochorous. From the above, you can see that with a few gaps, myrmecochorous Erythronium are distributed right around the northern hemisphere with the exception of western North America. That fact makes it virtually certain that the ancestral Erythronium from which all species of the genus are descended was myrmecochorous, and for some reason when the genus entered western North America that characteristic was lost.
A knowledge of which plants are myrmecochorous can have very practical value when we are growing the plants. With Erythronium the western species have very durable seeds because in nature they are dispersed by catapult action from erect capsules shaken by wind or a passing animal, and consequently they evolved with the ability to withstand desiccation for weeks or even months while waiting to be thrown from the open capsules. For us that means when seeds arrive in mid-winter from a seed exchange, we can if we wish, leave the packets in the fridge until the following fall in order to have the seeds germinate at the right time the next spring. Myrmecochorous seeds, including those of Scoliopus, require a very different treatment. They are adapted to being “planted” by ants in summer while they are fresh. Consequently, it is ideal to use fresh seeds, and one should expect the seeds to need a period of warmth while moist before they experience the coolness of winter.
When, after several years of trying, I finally obtained seeds of S. bigelovii, they arrived in midwinter, which put me in a quandary. I realized they would need a period of moist warmth followed by coolness, but I felt it was doubtful they would survive if I kept them until summer for their period of warmth. Instead of waiting, I improvised the following procedure, and as it was successful I am giving an account of it here, though possibly there are other procedures that would have worked as well. The seeds arrived on January 31 and I promptly placed them on sterilized moist sand in a sterilized container covered by thin plastic and I placed the container in a room with a temperature of about 22o C. during the day and about 16o at night. I left them there for two months. On April 1 I moved the container to my fridge with a temperature of about 4o C. A little over two months later on June 8, while still in the fridge, the seeds began to germinate, and over a period of two weeks all the seeds germinated. As they germinated I potted them in suitable soil and placed them in a north-facing window of an unheated room.
In nature Scoliopus plants go through the seedling stage during the cool weather of spring, but S. bigelovii is a very tough, adaptable species, and my plants were able to survive the warmth of summer. I did lose some during the winter, perhaps because they missed the natural period of rest after a normal spring of growth. Some actually still had partly green cotyledons in early March while their first true leaves were developing. I have had Erythronium dens-canis seedlings develop in the same way under the same conditions, but generally I have had little success raising Erythronium that germinated at the wrong time of year.
It was interesting to observe that the pattern of germination of Scoliopus appeared to be exactly like that of Erythronium. From each seed a slender, round shoot, the tip of which was the radicle (primary root), emerged and penetrated the soil. As it lengthened, it looped upward to form the cotyledon (seed leaf), which eventually pulled free of the seed coat and swung upward into an erect position. With some seeds the cotyledon pulled the seed coat free of the soil and retained it on its tip.
This pattern of germination of Scoliopus seeds needs further study, but it seems to be different from that of Trillium. I have limited experience with raising Trillium from seed, but I did closely observe the germination pattern of T. “hibbersonii” in a cold frame. (Strict nomenclatural accuracy, which probably does not reflect the true taxonomic status, has this plant as Trillium ovatum var. hibbersonii.) Fresh seeds planted in early September germinated in October and produced a radicle. The seeds then rested until early March, when each produced a relatively wide, flat cotyledon. Apparently this two-stage germination is the usual pattern for Trillium. It is possible that Scoliopus seeds planted in summer would also have a two-stage germination, though the slender cotyledon certainly does not resemble that of Trillium.
In addition to the way Scoliopus flowers are pollinated and the way the seeds are dispersed, there is a third phenomenon in the “secret lives” of Scoliopus that is the most secret of all, for to my knowledge no account of it has ever appeared in print. In two floras and in the otherwise excellent paper by Utech (1992), one finds the statement that the Scoliopus capsule opens “by decay”. There are reasons why that cannot be true, as you will see as I describe the “secret” third phenomenon. If one grows the plants in a garden where one can observe them every day, one soon notices that capsule dehiscence is a rapid process that takes place in only a few hours, and that the breaks in the capsule wall, though jagged, are clean and show absolutely no sign of decay. Furthermore, in my garden the leaves of the Scoliopus plants frequently hold the capsules well above soil that would induce decay, and those same conditions must often be true for plants in their natural habitats. I am not the only person who has noticed the clean breaks in capsules. An item originating with the USDA Forest Service and the USDI Bureau of Land Management (1994) and appearing on the Internet suggested that slugs may play a part in the dispersal of S. bigelovii seeds by eating capsule walls. That evidently was a good effort by observant people to explain the decay-free breaks in the capsule walls, but slugs are not a necessary part of the process of myrmecochory with Scoliopus, as no slugs have been nibbling capsules in my garden.
Having the plants in my garden has given me a great advantage over those who must study them in the wild. When something seems to be happening with my Scoliopus plants, each day after breakfast I don suitable clothes for the weather, take my camera and a magnifying glass and a piece of plastic to lie on, and stroll out into the garden. There I can spend a leisurely two or three hours watching the plants and making notes. It was in that way that I learned the secret of Scoliopus capsule dehiscence.
As I am not an early riser, often by the time I had reached a Scoliopus plant, a capsule that had been intact the previous day would have a conspicuous break in its wall. Within a short time a seed or two would drop free, or very likely an ant would have detected the scent from the elaiosomes and would be busy enlarging the break in the capsule to free the seeds. Evidently ants often do help with the dehiscence of the capsules, but I have seen seeds drop free before ants had discovered them. My S. hallii are in a rather cool, damp place seldom frequented by ants, and consequently there have been some years when the seeds were left where the capsules dehisced, and the following spring they germinated in a crowded mass where only a few would be able to mature.
There is an obvious reason Scoliopus capsules would not have evolved to dehisce by decay. During the many hours I spent observing and photographing ants reacting to Erythronium seeds, I soon learned that the ability of the elaiosomes on the seeds to attract ants lasts only a short time after the capsule dehisces and air reaches the seeds. Evidently the attractive substance in the elaiosomes is volatile and its scent quickly dissipates. I found that in the sun the seeds usually ceased to be attractive to ants after about two hours. This could well be part of the strategy the plants have evolved to make use of ants. Several times I have seen an ant pick up a seed and carry it away, only to lose interest in its burden after going a few metres, evidently because the scent had dissipated. It would then put the seed down and inspect it as if wondering why it had been carrying a useless object. The seed would then be abandoned and would be ignored by other passing ants. For the seed, the ants had served their purpose. It had been “planted” well away from the parent plant, and would spend the winter covered by leaves and debris.
The attractive power of Scoliopus elaiosomes seems to be more durable than that of Erythronium elaiosomes, perhaps because the plants grow in shadier, cooler places, but it also lasts only a brief time. If I placed day-old seeds in the path of ants, they would quite often pick them up, but equally often they would ignore them. A little over a day after dehiscence seemed to be the limit for the attractive power of the elaiosomes. Surely it must be obvious that for Scoliopus, myrmecochory could not be effective if dehiscence was by a slow process of decay. There remains the question of how the capsules achieve rapid dehiscence. With Erythronium the capsule dehisces along the midrib of each locule, and with myrmecochorous species the segments rapidly curl back to expose and drop the seeds. For some reason evolution has not allowed Scoliopus to have that method of dehiscing, but perhaps its method is better. The walls of a Scoliopus capsule have two layers of cells, an outer tough and durable layer and an inner more fragile layer. It seems almost certain that when the seeds are ripe, the inner layer of cells secretes a digestive enzyme which digests the cell walls of both layers, allowing the seeds to drop free. Generally the capsule breaks open near its outer end, but occasionally it splits open along one side.
As I am not equipped to do chemical analyses, the above explanation of capsule dehiscence is presented as an hypothesis, but there does not seem to be any other reasonable explanation for what I have observed. I am not aware of any other member of the lily family that uses such a method of dehiscence, and it may well be the most clearly unique of all the characteristics of this unique genus.
As I have mentioned, over the years a number of botanists have proposed linking Scoliopus with other genera to form families split from the large, diverse family, Liliaceae. The favourite linkage placed Scoliopus with Trillium and Paris. Utech (1992) summarized the efforts of various people from John Torrey, who in 1857 placed Scoliopus in the family Melanthaceae, through Sereno Watson, who in 1879 linked Scoliopus with Trillium and Medeola, to Arthur Cronquist, who in 1988 followed others in placing the troublesome genus in the family Uvulariaceae. Utech commented on the supposed Trillium connection that “Few character sets of . . . the family Trilliaceae match those of Scoliopus or convey its proper taxonomic position.” Utech’s words plus the evidence of the uniqueness of Scoliopus should end the belief that the genus has a close relationship to Trillium.
It does seem that Scoliopus has caused more than its share of problems for taxonomists simply by being unique. However, alpine gardeners will like the two species all the more for being unusual. They deserve a place in more gardens.
Dice, J.C. 1993. Scoliopus. In The Jepson manual: higher plants of California. Univ. Calif. Press, Los Angeles, CA.
Hitchcock, C.L., A. Cronquist, M. Ownbey and J.W. Thompson. 1969. Vascular plants of the Pacific Northwest. Part 1. Univ. Wash. Press, Seattle, WA.
Peck, M.E. 1961. A manual of the higher plants of Oregon. Binfords & Mort, Portland, OR.
Utech, F.H. 1992. Biology of Scoliopus (Liliaceae). I. Phytogeography and Systematics. Ann. Missouri Bot. Gard. 79: 126-142.
Utech, F.H. 2002. Scoliopus. In Flora of North America north of Mexico. Vol. 26. Oxford Univ. Press, New York & Oxford.
Information on the photographs for use in captions. The numbers below correspond to the numbers circled in red on the slides. All photographs were taken in the author’s garden.
- Scoliopus bigelovii. A single plant almost 20 years old photographed in early March.
- Scoliopus hallii. A group of plants that have been in the author’s garden for over 20 years photographed in mid-March. Notice the numerous recently germinated seedlings close to the parent plants which resulted from ants failing to find the seeds the previous year.
- A gnat on a Scoliopus bigelovii flower. The gnat so perfectly illustrates the ability of gnats to pollinate the flowers that it seems posed, especially as the flower happens to have one stylar arm unusually low and it has contacted the gnat, but the photo could not be posed with such a tiny, delicate insect. The photo is an example of Sod’s Law working in reverse.
- Gnats on a Scoliopus bigelovii flower (A second gnat is on the sepal in the rear.). This photo is provided in case #3 is too perfect.
- Gnats on a Scoliopus hallii flower.
- Ants obtaining seeds from a Scoliopus bigelovii capsule. In this photo and the next the raised ridge along one side of each seed is the elaiosome. In both photos notice that the breaks in capsule walls are fresh and clean and show no sign of decay.
- Ants obtaining seeds from a Scoliopus hallii capsule. The capsule in the foreground had opened the previous day and was emptied of its seeds then.
Notice that I cannot be sure all the gnats are fungus gnats, and consequently it is best to identify them simply as gnats. The larvae of some fungus gnats as well as those in related families feed on decaying vegetation. Utech (1992) identified the insects pollinating both Scoliopus species in their natural habitats as fungus gnats. –>