There exists a small flowered form of yellow lady slipper orchid occurring over much of the northern US, across southern and central Canada, as far south as the northern Rocky Mountains, and northward to the Yukon and northern Alaska. It is the well known, but not often encountered, Cypripedium parviflorum v. parviflorum. In appearance it looks very close to the European species, C. calceolus, and in fact until fairly recently was considered a variety of that species.
Without a doubt, C. parviflorum is the most variable Cypripedium species both in terms of morphology and habitat preference in North America. In all not less than two dozen names have been given to this species at the level of specific or varietal rank – a tribute to the variation within plants seen in the field. This has lead some authors to consider C. parviflorum to be either a very diverse grouping of one species, or on the other extreme, to place them into a number of different species and/or varieties. Today, most botanists have agreed to disagree and call all North American plants C. parviflorum, with at most three varieties in existence: two small flowered plants, v. parviflorum and v. makasin, and one larger flowered form, v. pubescens.
To further confound things, even the small flowered plants don’t quite fit any easy classification. The one attribute that seems constant across the range of plants now known as v. parviflorum and v. makasin is they all have smaller flowers when compared to the larger flowered v. pubescens. In fact it is this attribute that in the end holds this rather uncertain classification scheme together. For purposes of horticultural interest, I will speak of the two small flowered forms as distinct varieties since they clearly are different in form and cultural needs.
The small yellow lady slipper is a perennial, deciduous, terrestrial orchid of generally moist to wet habitats. Like the flower, the plants tend to be smaller in size compared to v. pubescens, averaging between 15-30 cm tall, with v. makasin commonly being a smaller plant than v. parviflorum. The thin stem is lightly pubescent and usually carries 3-4 lanceolate leaves held opposite each other, 3-10 cm long, and 1-3 cm wide. They are usually a pleasing apple green and also are lightly pubescent. The rhizome is thick and clumping with numerous roots.
One or two flowers (rarely three) grace the apex of the stem, each attended by one floral bract. The flowers are small, not more than 4.5 cm in total spread, and often smaller. The dorsal sepal is held more or less erect and is often twisted with undulating margins, 2-4 cm long and around 2 cm wide. The synsepal is similar in shape, but is held much more flat than the dorsal sepal, and is bifurcated at its apex. The slightly descending petals are relatively long and narrow, and twist 2-4 times forming a light braid, 3-5 cm long and less than 1 cm wide. The lip averages not more than 3 cm in length and in extreme specimens can be half that size. It ranges from ovoid to ellipsoid in shape and has a small orifice. The staminode is elongate and roughly triangular in shape.
Flower color is somewhat variable except that the lip is virtually always a clear, rich lemon yellow. The sepals and petals tend to be similarly colored on any given plant with a light green-yellow base color, and yet looking brown to dark brown in overall color. This is due to spotting and blotching of said flower parts, forming anything from a near pure dark purple-brown look (typical of v. makasin) to a more striated pattern. The lip is often spotted and blotched with crimson or brick red, especially in its interior and around the orifice margins. In extreme examples this red blotching can occur over the entire lip – a more common occurrence in western forms of v. makasin. The yellow staminode as well is often blotched with crimson. Variety makasin is well know for its intensely sweet odor, while v. parviflorum has a more subtle floral scent.
These two small flowered varieties have distinctly different ranges, with v. makasin favoring the far north and west, and v. parviflorum more southern and eastern regions. Specifically, v. makasin can be found from northern New England, throughout much of northern New York, northwest Pennsylvania, northernmost parts of Ohio, Indiana, and Illinois, most of Iowa, and northward to Newfoundland, through the southern half of Quebec, much of Ontario, the southern third of Manitoba, central Saskatchewan, most of Alberta, and the eastern half of British Columbia. It is also found southward down the mountains into western Washington state, the Rockies of western Montana, and northward into the Northwest Territories, the Yukon, and the mountains of northern Alaska. Two disjunct populations have been recorded in extreme northeast Utah, and the northwest corner of California (based on one collection in Sierra County).
Variety parviflorum is found from southernmost New Hampshire, Massachusetts, Connecticut, southern New York, northwestern New Jersey, southeastern Pennsylvania, Maryland, Delaware, Virginia, West Virginia, the piedmont and mountains of North Carolina and South Carolina, northern Georgia, northern Alabama, Tennessee, Kentucky, extreme southern Ohio, northern Arkansas, southern Missouri, and the extreme eastern edges of Oklahoma, Kansas, and Nebraska.
The two varieties are also at odds with regard to habitat. Variety makasin is most commonly found in wet habitats such as wet prairies, fens, bogs, and swamps with calcareous soils, while v. parviflorum seems to prefer drier deciduous woodlands in acidic soils. It is said that this form prefers more acidic sites than its bigger cousin, v. pubescens.
Given the distinct differences of the two varieties, there has been much discussion about them. The most obvious and cohesive group is v. makasin in the eastern end of its range. Virtually all of these plants have a very similar appearance and grow in the similar habitats. They comprise the “typical” form of what used to be called Cypripedium parviflorum – very small plants with dark sepals and petals, and little or no red spotting on the lip’s outer surface. Unfortunately, as you move westward, variation within v. makasin increases, and one is left with the idea that maybe these plants are distinct from the eastern ones. The more southern growing v. parviflorum is no less difficult to handle. It can intergrade (in terms of characteristics) with v. pubescens so that clear distinctions may be difficult to discern in some plants. For this reason some authors place v. parviflorum within v. pubescens. Certainly these plants are not the “typical form” of the original “C. parviflorum” concept.
In the end we are left with more questions than answers. Still, the general wisdom seems to favor the model of a highly variable, yet single species. Some authors (notably Sheviak) support the idea that v. makasin is distinct from v. parviflorum, yet significantly others do not, for example Cribb. In his seminal monograph “The Genus Cypripedium” Cribb states: “The distinctiveness of vars. parviflorum and makasin is, I believe, practically impossible to see in herbarium material, and Sheviak’s photographic comparison of them is unconvincing.” And so, things remain unclear, at least from the position of trying to name all the various forms out in the field.
An odd, outlying collection of v. makasin made by Alice King (undated) from Sierra County (Union Hill) seems to be a single instance of this species in California. Such odd collections happen from time to time, and may represent mistakes or simply may be due to one off plants of remnant populations. Utah populations as well, if they still exist, are no doubt very a rare these days. I’d also like to know more about populations of v. parviflorum that are supposed to exist in Delaware and New Jersey, and for that matter southern New York. I suspect these ranges are historical only and if you look for them nowadays you will be left scratching your head. Certainly in all my years looking in southern New York I never came across one yellow lady slipper, large or small.
My experience with this species goes back to when I was a teen. At the time I had orchid fever and had looked (with my father) high and low for this plant in the woodlands of southern New York state. We never did find one, though stories abounded of plants “in the high hills of those woods over there”, etc. Maybe they still existed there at the time (the late 70s), but I doubt few do anymore. We did grow v. makasin for many years, as well as v. pubescens. Both seemed rather easy in the acidic rocky soils of northern Westchester County, though years later I learned their preference for more sweet soils.
After high school I moved to Florida to go to college and gave up on Cypripedium cultivation. Then in the early 90s I began taking hiking trips into the southern mountains of Georgia, North Carolina, and Tennessee. During these excursions I came across my old love – Cyps in the wild. This kindled my passion for the genus and I began the unlikely endeavor of trying to grow them in Florida – a place ill suited to any Cyp. To mitigate the high temperatures of summer, I grew C. parviflorum v. makasin and C. reginae in pots in a “reverse cycle” scheme, that is, growing them under lights in a cool porch in winter and then giving them a “winter rest” in the dead of summer by putting the pots in plastic bags and vernalizing them in the refrigerator for 4 months. In this way I managed to keep both plants alive and even got them to flower – in fact v. makasin was very reliable about flowering even under these less than perfect conditions.
Jumping ahead another five years I again tried my hand at v. parviflorum, this time in southern Japan. I got hold of seedling plants of v. parviflorum, and after 5 years managed to get a couple close to flowering size. Then, in 2011, a mysterious fungal infection knocked back many of my Cyps and the v. parviflorum were killed outright. My conclusion is that this variety needs colder temperatures than local conditions can provide.
So what do these plants require? In my experience v. makasin is an easy plant to grow and flower if you live in the right climate. Given proper conditions it can readily clump and responds well to division, so making many more plants is possible. All that is required is a well draining, yet continuously moist substrate with a slightly acidic to neutral reaction. While plants in the wild often grow in wet conditions, this is not required in culture and could lead to rot problems. This is a plant that can withstand some sun, though sun in the morning and high shade the rest of the day is optimal. Any reasonable compost may be used – figure at least 50% inorganic materials such as sand, gravel, pumice, etc, and the rest a mix of a good woodland loam with some organic content. Avoid truly acid materials such as “top soil”, conifer needles, or peat moss. Sedge peat in limited quantity can work well with this variety as long as it is mixed with generous amounts of silica sand, perlite, etc. This is not a fussy plant.
As for the more elusive v. parviflorum, you need to think of a more acidic compost, though not as much as C. acaule requires. Drainage is important with this form, so I would recommend coarse structured materials such as pumice, gravels, as well as commercial brand products such as Soil Perfector, Turface, and the like mixed with a good acidic woods loam at the rate of around 2:1. In nature these plants occur in deciduous woodlands, often in hilly areas or mountain tops that are very well drained. By all accounts this is the more finicky of the two small flowered varieties to grow, and most certainly is more difficult to obtain in the trade.
Given their different ranges, v. makasin and v. parviflorum have different temperature requirements, with the former being more cold tolerant of the two, and the later more heat tolerant. Nevertheless, both should be quite cold hardy, especially v. makasin, which should be fully hardy to USDA cold hardiness zone 2 and can be grown up to zone 6. Variety parviflorum is perhaps less resistant to extreme cold, but still should be fully hardy to at least USDA zone 4, and southern derived plants can perhaps even endure zone 7b.
In the wild v. makasin is sometimes found growing alongside Cypripedium candidum, and in such mixed colonies the resulting natural hybrid, C. x andrewsii, can be sometimes seen. This plant is intermediate in color with the parents, having generally strongly colored sepals and petals as well as a lovely white lip. It is very easy in culture, forming clumps in a relatively short time. Like its parent C. candidum, it favors sunnier conditions than most Cyps, and prefers neutral to basic composts. Variety makasin has also been used in a number of artificial hybrids, notably C. Gisela (x C. macranthos) and C. Emil (x C. calceolus). Most of these have proven to be very vigorous growers – much easier than the parent species under “normal garden” conditions.
If you get the chance I highly recommend growing these lovely little slippers, in particular v. makasin. This is a plant that delights the senses not only due to its tiny stature (yet robust habit), but also because of its richly colored flowers, and intensely sweet odor. If that weren’t enough, it is one of the easiest Cyp species to grow. I ask you, how could you resist such a plant?