Cypripedium reginae, the showy lady’s slipper

Surely the most resplendent of lady’s slipper orchids in North America is the aptly named showy lady’s slipper, Cypripedium reginae. It is a rare, yet locally abundant plant of swamps, bogs, and wet woods throughout the northeastern quarter of the US as well as adjoining areas of Canada. Even as little as 50 years ago it could be seen over much of the midwest and northeastern states, with some populations numbering into the many thousands of flowering stems, but sadly the plant is now endangered or on the verge of extinction in many areas. Reasons vary, however modification of habitat and an exploding deer population probably figure in strongly for the losses over the past half century. Luckily, breakthroughs in seed propagation since the mid 1980s have made this plant fairly common in the horticultural trade, so the plant’s future seems secure, at least as cultivated stock.

Cypripedium reginae is a large herbaceous, deciduous, perennial, terrestrial orchid of wet habitats. The thick, thumb sized growth buds poke up a bit later than most other species of Cypripedium, and over a month’s time can grow into plants approaching a meter tall. It’s stem typically is a bit shorter, between 40-75 cm on average, and supports between 3-7 highly pubescent leaves. The leaves are borne alternately off the stem, are somewhat elongated, yet generally ovate, and deeply ribbed. The stem and leaves are highly hairy and can cause allergic contact dermatitis if handled. The root stock consists of a branching, thick rhizome with many cream to white colored roots that can grow over 70 cm in length. When happy this species can form clumps over 50 flowering stems, something that is almost hard to imagine.

Flowers are borne at the apex of the growth stem, as many 3 per stem (rarely 4), and each is accompanied by a floral bract. The flowers are, like the rest of the plant, large in size with a natural spread up to 10 cm from petal tip to tip. The dorsal sepal is broad and stands more or less erect, growing up to 5 cm long and ovate with a rounded tip. The synsepal has a similar shape, and is perhaps a bit smaller in size. The petals are elongate and fairly narrow, growing up to 4.5 cm long and under 2 cm wide. They are held flat (sometimes slightly recurved) and nearly parallel to the ground. The lip is round, though somewhat elongated, like an egg. It’s orifice can vary from being quite wide to small . The staminode is broad and like the dorsal sepal is ovate, fully covering the column.

The thing that makes this flower so singular are its colors – truly those of a queen. The dorsal sepal, petals, and synsepal are absolutely pure white, and I do mean pure white. The lip has a white base color and is suffused with purple-pink – sometimes as a light blush, sometimes so thick that it seems entirely deep purple, but often this flushing is in parallel lines creating an alternating purple and white striped pattern. The staminode as well is pure white and typically has yellow blushing on its lower half accompanied by purple-pink blotches and spots. Pure alba forms exist as well. Flowering commences in mid June and can extend into July in the far north of its range. Interestingly, flower color can vary widely from year to year and this appears to be dependent on ambient temperatures with cooler conditions producing richer casts.

The showy lady’s slipper once inhabited much of northeastern North America, extending from the boreal forests of the southern Canadian Shield to the Great Lakes and beyond, throughout the cold temperate regions of the east coast, and down the Appalachian Mountain chain nearly to its southern terminus. In more recent times it has been recorded in Canada from the extreme southeastern corner of Saskatchewan, extreme southern Manitoba, southern and central Ontario, southern Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Miquelon Island, and almost all of Newfoundland. In the US it has been recorded historically from virtually all of New England (except Rhode Island) and westward to eastern North Dakota, south to Iowa, Illinois, Indiana, Ohio, West Virginia, Maryland, northern Virginia, and northwestern New Jersey. Sporadic populations also existed along the Appalachians from southern Virginia, to Tennessee, and into North Carolina, as well as on the Cumberland Plateau of Kentucky. An odd, disjunct population also occurred in the region of the Ozark Mountains in south central Missouri and extreme northern Arkansas. Correll (1950) cited a possible collection in northern Alabama around the Huntsville area, but to my knowledge that has never been confirmed. The same author reported this species from western China based on herbarium specimens, but clearly he confused it with the related species C. flavum.

Sadly, many populations have undergone severe range restriction, especially in areas of extreme human activity (for example the southern Great Lakes region and metropolitan areas on the eastern seaboard), and also across much of the southern end of its range. The status of the plant today in the US is as follows, by ranking and state:

Probably Extirpated: Kentucky, Maryland, and North Carolina.

Critically Imperiled: Arkansas, Connecticut, Illinois, New Hampshire, New Jersey, Tennessee, Virginia, and West Virginia.

Imperiled: Iowa, Missouri, Ohio, Pennsylvania, and North Dakota.

Vulnerable: Indiana, Maine, Massachusetts, New York, Vermont, and Wisconsin.

Unranked/Under review: Michigan and Minnesota

In Canada it is critically imperiled in Saskatchewan; imperiled in New Brunswick, Prince Edward Island, and Newfoundland; and vulnerable in Manitoba and Quebec. Only in Ontario is the species considered “apparently secure” – the only place in the entire range of this species that its status is known to be safe.

Clearly, C. reginae is in trouble in the wild. Southern populations exist only as remnants and are subject to extirpation within the next few decades. As a sample case, consider that before 1980 this species was found in 11 counties in the state of Pennsylvania extending from the shores of Lake Erie diagonally across the state through the central ridges down to the Maryland border. One population even existed in the Leigh Valley in Northampton County, adjacent to New Jersey. After 1980 populations diminished down to just four counties – Crawford, Erie, and Lawrence (all in the extreme northwest corner of the state), and Cumberland in the south central area near the Maryland border.

The same pattern applies to much of its range in Connecticut, New Jersey, North Dakota, and even large sections of Massachusetts where it was once quite common. Two states that still harbor large populations are Michigan and Minnesota, but neither state has been ranked recently to my knowledge, no doubt due to rapidly changing conditions on the ground.

This is a plant of wetlands, in particular on the edge of calcareous fens, and in open swamplands where red maple (Acer rubrum), black ash (Fraxinus nigra), larch (Larix laricina), arborvitae (Thuja occidentalis), and balsam fir (Abies balsamea) often are the dominant tree species. In places sphagnum moss species can be seen growing luxuriantly, implying an acidic substrate, but in truth the mucky soils of such swamps are often neutral or basic in reaction. In the more open, sunny places C. reginae can form extensive colonies covering large areas, but excessive shading leads to their eventual diminishment.

Plants in the south can be found in more novel habitats for the species. In Missouri they seem to colonize wooded slopes with limestone outcrops while it is said that in North Carolina you could find them in open deciduous forests “between ridge lines” – implying a valley bottom or at least a saddle between ridges. Plants in such conditions represent glacial relic populations, not the norm.

The false hellebore, Veratrum viride, in early leaf looks remarkably similar to the showy lady’s slipper with the exception that the leaves tend to be borne in a spiral pattern as opposed to the alternating pattern of the orchid. I remember vividly coming across a huge population of false hellebore on a middle school trip and thought I hit the jackpot – hundreds of C. reginae! Returning home I eagerly told my dad the news. He was surprised and then asked if I’d seen any flowers. I said no and he replied that he doubted they were in fact C. reginae, but rather the look alike hellebore. We made the one hour drive north to the location a week later and indeed confirmed my mistake without question – the plants were all in bloom with tall spikes of tiny green flowers. Sometimes dreams die hard.

A few odd facts about this plant before moving onto its culture. First, it contains a phenanthrenequinone known as cypripedin that can cause allergic contact dermatitis in sensitive people. Oddly enough, it is this same chemical that has made several Cyps a folk remedy for a number of illnesses. This class of chemical has shown antimicrobial and cytostatic properties, as well as the allergic response. If you are given to rashes I would be careful handling the plant’s leaves, though I would not consider this to be a risky plant to have in your garden since its toxicity is low.

Second, this species was first described under its present name in 1788 by Thomas Walter in his comprehensive manuscript “Flora Caroliniana” from a collection he made in the mountains of western North Carolina. This is pretty odd given the rarity of the species even in those days in the southern mountains – one would have expected the type material to have been found from the north where it was abundant at that time. In fact it only has ever been recorded from two counties in the high mountains of southwestern North Carolina – Macon and Jackson. To my knowledge plants in that area have passed into legend decades ago. To add to the intrigue, Walter died just one year after his botanical treatise was published, in 1789, at the age of just 49.

Third, when hybridized with other Cypripedium species, the characteristics of the offspring are often dominated by C. reginae. For example, when crossed with the Chinese species C. lichiangense somewhere around 80% of the resulting plants have flowers nearly identical to C. reginae and the plants themselves are very similar. The other 20% will have an intermediate appearance, a very striking plant with flowers approximately halfway between the parent’s, and indeed the plants themselves are an odd blend. They are much shorter in stature than C. reginae and also have mildly spotted leaves like the parent C. lichiangense. This dominance pattern seems to be especially true if the seed parent is C. reginae – so when making crosses it is advised that it be the pollen parent. There has been considerable discussion about C. reginae crosses and why this species seems to dominant. Opinions range from people saying look alike “hybrids” are the result of flowers that have been pollinated by bees and so are in fact the pure species, or perhaps an unusual form of asexual reproduction has taken place known as apomixis. Others maintain characteristics of C. reginae just dominate in its hybrids.

Despite being a rarity in the wild these days, this plant offers no problem in the garden if it is in the proper climate and certain steps are taken to keep it happy. First and foremost, this is a plant of cool to cold temperate regions. If you attempt to grow it in areas with high summer temperatures and mild winters you are probably going to be disappointed in the end. In the eastern USA this plant seems at home in USDA cold hardiness zones 6 and lower, but unsuitable for anything higher. Numerous reports have come out that C. reginae is a non-starter in zone 7 in this region. I’m not saying you can’t succeed, but the chance of failure is high. In climates with cool summers you can grow this one even in zone 8, for example the coastal areas of the Pacific Northwest or southern England. I would say it is ideally grown in zones 3-5.

This is a forgiving species with regard to soil thankfully. Any good garden soil that is not too acidic or too loamy will suffice. Like other Cyps, in culture it likes an airy substrate that remains continuously moist, not wet. While it is true that in nature this is a species of wet, even mucky soils, I highly recommend you don’t attempt to grow it that way in culture. Much has been written about making “Holman type” bog gardens for this species and Cyps in general, and indeed people have been successful in growing them that way, yet I would not recommend it. The problem is that wet soils can break down and spoil within just a few growing seasons and cause problems in the long run.

Instead choose any good gritty material such as perlite, fine pumice, silica sand, or name brand products like Turface, Soil Perfector, etc. and if you want, add some organic material to it. Some people have reported that coir (chunks of coconut husk) added to the mix helps in overly moist conditions to loosen the compost. Ron Burch grows his plants in totally inorganic compost and has found plants respond much better than those grown in true soils or soils high in organic components. Still, under normal garden conditions, this species is highly tolerant of many soils. Aim for a pH near neutral with good soil structure and even moisture, and you are likely to succeed.

One thing, this plant requires some sun during the day, preferably morning or late afternoon, though the former is better. Overhead, midday sun is not a good idea since this will stress the plants. Shoot for full sun from early morning to about 11 AM and then bright shade the rest of the day. High shade or a north facing wall with no tree cover work very well too for his plant. Plants grown in too much shade will become spindly, stop flowering, and slowly diminish.

A well grown garden specimen can be an incredible thing, having 50 or more flowering stems with 1-3 flowers per stem… you do the math! There are reported specimens with a hundred plus flowering stems. I don’t think I can even imagine the visual impact of such a plant.

Happily, this species is easily grown from seed these days and has been distributed across the globe in gardens from the USA and Canada, thru Europe, to Japan, and possibly even Australia. Much thanks has to be given to early experimenters – in particular Carson Whitlow and Bill Steele in America, and Werner Frosch in Germany. It is one of the more affordable Cyps on the market, with flowering size divisions available for as little as $25US. Not so here in Japan, where a single growth can fetch $80US or more. Even the alba variety has become fairly available worldwide.

A true queen among a genus of exotic and unusual flowers, Cypripedium reginae is among the choicest species even to this day. Not to beat a dead horse, but if you see them in the wild, appreciate them, photograph them, but leave them be. There is no excuse to collect wild plants unless they are subject to imminent destruction. Instead, buy them from one of the many reputable vendors who produce and/or sell artificial stock.