Propagation of Native American Cypripediums
by Aaron J. Hicks
Many of our donors request seed of Cypripedium species. If you are not familiar with the seed propagation of these species, you are strongly advised to carefully consider the following comments. Cypripediums are desirable, but propagation of these species via seed is not a trivial matter. The vast majority of orchids require specialized conditions under which to germinate if we are to produce an acceptable number of seedlings. Cypripediums are even more demanding, requiring specialized disinfection techniques, special media, and sometimes peculiar temperature regimes.
The first thing to consider is whether or not your cultural conditions will permit cultivation of members of the genus. These temperate terrestrials require a cold resting period, and are therefore
unlikely to survive from year to year without several months of cold weather. Without refrigeration or (preferably) naturally cold conditions, they will perish.
The second thing to consider is whether or not you have the correct media upon which to raise these species. Although some temperate terrestrials (paphiopedilums, phragmipediums) germinate well on media
formulated for tropical epiphytes, the greatest success with growing cypripediums from seed will be achieved using media formulated for this genus.
There are several excellent sources for details on these media. Some growers, such as Bill Steele of Spangle Creek Labs, utilize a modification of
Harvais' (1982) medium. This formula was written up for the North American Native Terrestrial Orchid Society, as part of the conference proceedings in 1996. Copies are available for $25 for the
paperback copy from:
North American Native Orchid Conference
14320 Poplar Hill Road
Germantown, MD 20874
The 1989 NANTOC proceedings are available through the Brandywine Conservancy bookstore: (610) 388-8326
Also noted in the NANTOC proceedings are the formulae for media that utilize amino acids for
cypripedium propagation, as written by Svante Malmgren. These media use different nitrogen sources than "traditional" media that are generally used for epiphyte. Some growers have had
success using commercial amino acid preparations, such as Sigma's RPMI amino acids; others use health food store amino acid preparations. Bill Steele has had good results recently using casein
hydrolysate at 200 to 400 mg/L, either singly or in conjunction with ammonium nitrate.
What may be another important factor in germination of cypripedium seed is whether or not the seed has been refrigerated. For temperate terrestrials, most species must be refrigerated for at least 3
months prior to attempting to germinate it. With only a few exceptions, all cypripedium seed shipped from the OSP has been refrigerated at least that long before we ship it out.
Lastly, cypripedium seed is unusual in that it often contains germination inhibitors that must be destroyed prior to successfully producing seedlings. There is some discussion as to whether these are
inhibitors being burned up, or the seed is "wetted" through the aggressive treatments outlined below, and their importance seems to vary between species. All the same, rigorous bleaching
is required for at least some species of Cypripedium to germinate. For those species that require it (see Steele's excellent article, as above), the seed is disinfected as usual- but the time is extended to the point where the inhibitors are burned up. This can take as little as 30 minutes, or as long as 4 hours. Steele uses a 10% bleach solution, for as little as 20-40 minutes for species like Cypripedium kentuckiense, to 2-6 hours for Cypripedium acaule.
Again, referring to Steele's article will be most helpful for those that wish to grow cypripediums from seed.
Scott Durkee, of The Vermont Ladyslipper Company uses Steele's techniques for propagation of cypripediums, and expects to have several species for sale later. At this point in time, he has mature specimens of Cypripedium reginae available as being propagated from seed. He has also had success in flowering Cypripedium acaule from seed, which has proven to be a difficult task in the past. His technique differs from others in that his feed water has been acidified to between pH 4 and 5 through the addition of cider vinegar. Although there are no clear reasons as to why this works, Scott believes that the acidic environment destroys pathogens that have caused failure to thrive or death in other attempts to grow C. acaule.
In conjunction with a watering schedule that tends to keep the plants dry, Scott has had success in growing and flowering seed-grown plants of this desirable species.
Although the OSP has offered cypripedium seed for sale almost since its inception, we find that success is generally low for different reasons. We provide seed first to conservation efforts, and then to
hobbyists and growers, in an effort to try to land as much seed as we can into the hands of experienced propagators. It is expected that as word is spread that these species are now available as
live, propagated plants with reasonably high expectations of survival (something that can not always be said of specimens dug from the wild) will gain popularity. Soon, it may be possible to have a
collection of slipper orchids in your own garden.
The OSP will continue to provide orchid seed from donors who strive to provide other growers with legally and ethically harvested seed in an effort to promote the cultivation of these species "in
captivity." Before long, perhaps we will be able to provide enough plants in cultivation that we can make a serious dent in "diggers" and other unethical operations. We look forward to
progress on this front.
News update 4/28/00
PhytoTech Labs now sells Malmgren's medium and Steele's 1996 modification. They are not listed on their webpage! Malmgren's is listed as M 551, and Steele's variation is T 849. These media may be used for the germination and culture of cypripedium species; previously, growers had to formulate their own. Bear in mind that both Malmgren's and Steele's media have many minor variations in order to produce optimum results with individual species; growers are encouraged to read more about these in the NANTOC Proceedings and elsewhere to determine which variations are best applied to culture the species of interest.