Environment and The Delight of Petrocosmea Hybridizing

A trio of flowers of siblings from a cross of P. 'Asa Blue' x begoniifolia. L to R are P. 'Keystone's Barnswallow', P. 'Keystone's Bluebird', and P. Keystone's Whipporwill'. This cross has had amazing variation among the flowers and leaf types produced.




When I saw the first seedpods developing on P. rosettifolia three years ago, I was ecstatic! I litterally skipped around like a little girl who's just been given a new pony! Ten years of attempting to get a Petrocosmea flower to produce seeds had finally paid off....now, the question was...."What did I do differently?" Why had it happened this time and not any of the hundred attempts before? Being schooled as a nurse in a nursing program where the model taught me to consider the environmental factors and stressors as factors that impact outcomes, I decided to take a moment and study what factors in the plant's environment were different this time and how were they different. Without boring you with all the details, when I studied this, I came up with two key differences this time....humidity and temperature. After testing those factors for anther year, and documenting my variables and factors...I am convinced that these two factors must be just right for both successful pollination and germination of the seeds to occur.

The first flower to open in the P. 'Asa Blue' x begoniifolia cross. This flower is quite large, with yellow, purple, and white in the flower. Petals are six in number, with slight ruffling, and white fantasy splashes in the flowers. I want to test this plant and future bloom cycles to make sure these qualities are stable before naming and releasing it, but WOW, what a flower!

Humidity is a major factor in successful pollination. I've now tested this several times and have found that unless the flowers being pollinated are grown in very high humidity, such as is found in an enclosed or terrarium-like environment, successful fertilization is rare, and seed production if pods developed, is zero percent! Only once have I gotten seedpods on flowers outside of an enclosed environment, and that time, all three pods were totally empty of seeds. This was also the only time I've gotten a "false" pregnancy with empty seedpods. Inside an enclosure, I am getting approximately 33% success.

Petrocosmea 'Rosemary Platz', my first named Pet hybrid, named for a beautiful lady and a dear friend of mine. The result of that first cross, which was P. rosettifollia x sericea. You can see that the yellow central veining in the leaves of P. rosettifolia was passed along to this hybrid. Flowers look like huge lavendar P. rosettifolia flowers. The plant got it's leaf size and shape and flower color, from P. sericea.

P. 'Keystone's Bantam',(rosettifolia x sericea) named for my friend Paul Kroll's prized bantam chickens, is the sibling of P. 'Rosemary Platz' shown above. This plant is tiny...never exceeding three inches in diameter. From the point that it germinated, this seedling was always very tiny and a bit of a slow grower. Leaves are deep green with yellow veining like P. rosettifolia, and the flowers are very large for the plant size and pure white with light green throats. The little plant blooms very heavily, although it is a strong seasonal bloomer for me. I selected it for it's miniature size and beautiful white flowers. I have used it in one cross with P. forrestii in the hopes of producing miniature Pet hybrids... SO far, the seedlings are all even tinier than 'Keystone's Bantam'.

P. 'Keystone's Harvest Moon' (rosettifolia x sericea), another remarkable seedling resulting from the first cross. These leaves are not chlorotic...This plant shows an incredible yellow blushing over the entire leaf surface in good light. The yellow veining is also present in the leaves, but the entire center of the leaf is yellow with a dark green margin. LOVELY! Flowers are lavendar and look great above the yellow foliage. It is now in bud and I hope to post some photos of the entire plant in bloom soon.

The second factor that seems to play a major role in successful fertilization is temperature...cool temperatures. Although temperature is slightly less a factor, I do believe it plays a role in both fertilization and germination of Pet seeds. My successful crosses have only occured with room temperatures of 45 degrees F or less. Above that, and I have less success, even with flowers that were grown in enclosed environments. In warmer temperatures, fertilization did not occur. As the temperatures dropped, I once again began having success. With regard to germination of seeds, this has been reproduced by several growers and myself now several times. In warm temperatures, germination was poor or failed to occur. When I placed the seed containers in cooler rooms, germination improved significantly and was even "heavy". Experienced growers of gesneriads from seeds have had the same results when I've shared Pet seeds with them.

I continue to study these factors on a daily basis with my Petrocosmea hybridizing program. I attempt to study the effect of temperature and humidity seperately and together. If you have Pets in flower, you must try to make some crosses. It is great fun and there is so much to be learned about this genus and it's culture. Keep notes of everything you do and the factors observed when you do it. Reviewing those notes in the future will likely be amazingingly instructional.

I'll post more on the factors involved in hybridizing Pets in future posts. Stay tuned!

Petrocosmea 'Keystone's Barnswallow' - Introducing a New Petrocosmea Hybrid!

Petrocosmea 'Keystone's Barnswallow' - the flowers are deep blue/purple with a white halo effect at the base of the upper two petals and two yellow lines in the throat.



Having an opportunity to introduce one's own hybrids is always great fun. I'm excited to be able to introduce a new Petrocosmea hybrid - Petrocosmea 'Keystone's Barnswallow', the happy result of a cross utilizing the new Japanese hybrid 'Asa Blue' as the seed parent and the species P. begoniifolia as the pollen parent. From the very beginning this has been an exciting hybrid cross!

The cross was exciting for a number of reasons. First, it was a Petrocosmea cross, that alone is exciting, since there have been so few! Hybridizing Petrocosmeas, while I've been fortunate to have some success, has not been easy. Sixty seven percent of the time, I fail to produce seeds when I attempt a Pet cross. Secondly, though, this cross in particular was a breakthrough because it utilized a Pet hybrid as a parent. I believe it may be the first successful Pet hybrid utilizing a hybrid as a parent, ever! The few that have been made, so far, have always been primary crosses between two species. This cross proved that at least some Petrocosmea hybrids are fertile. It is only the second cross, that I am aware of, that utilized P. begoniifolia as a parent. I was interested in using this species because it has white flowers, it has yellow in the flower, and it has purple pigmentation in the leaves and pedicels and peduncles as well as the the calyx lobes. I felt that introducing purple pigmentation into the plant's various parts would be an exciting characteristic of hybrids. So, there were lots of high hopes for this cross...and it has exceeded my hopes!

The cross produced two full seedpods and lots of seed. I had good germination, and from the early stages, I could see a good deal of variation in the leaves on the baby plants. The cross has P. begoniifolia, nervosa, and flaccida in it's background, and among the 30 seedlings that I am growing out, I can see plants with dominant features of each of the three species in the foliar characteristics. I was very happy to see that many of the plant began to bloom at an early age, and for young plants, are still producing lots of buds and flowers. This definitely comes from the 'Asa Blue' parent, which blooms heavily, over a long period, and blooms as a quite young plant. The plants are taking on a very pleasing leaf symmetry and shape from a very early age.

A photo of the whole plant. This photo shows P. 'Keystone's Barnswallow' in a three inch pan pot. Foliage is showing a bit of chlorosis in the photo due to the plant being placed on shelf with new T-8 lights and getting a bit more light than it likes, however prior to this, the plant had lovely deep green, glossy foliage with the nice pebbling effect that begoniifolia has. Flowers are a pleasing contrast of deep blue against the green foliage. There are still lots of flower buds underneath those leaves!

A photo of P. 'Asa Blue', the seed parent of my cross. P. 'Asa Blue' is a remake of the cross that produced P. 'Momo' the first Pet hybrid. The cross is P. flaccida x nervosa. 'Asa Blue' produces flowers of a medium to light lavendar, while 'Keystone's Barnswallow' has much darker blue/purple flowers that hold the deep color until they fade.

The pollen parent for 'Keystone's Barnswallow' ...the lovely species P. begoniifolia. I chose it in the hybridizing effort because of the flower shape, it's white color, with yellow in the throat, and the purple pigment in the calyx lobes and pedicels as can be seen in this photo.

The cross has produced a lot of good flowers, but several have been discarded as "nothing new". I have selected five so far to keep and evaluate further. P. 'Keystone's Barnswallow' is surely the best so far. Across all of my hybridizing efforts, I am selecting seedlings for two qualities in general.... 1) early, and prolific flowering across a long period, 2) attractive, ornamental foliage that shapes well and does not tend to offset easily. With individual crosses, I may have other goals. This new hybrid I feel, meets both goals. 'Keystone's Barnswallow' began flowering in early June and has been in continuous flower ever since. It has at least 15 more buds that I can count underneath the foliage. And, while several of it's siblings have formed offsets, it has not and shows no sign of doing so at this point.

The Parryorum's are in bloom.....

Single flower of Petrocosmea parryorum.



For me, the blooming of Petrocosmea parryorum is a thrilling event. Well, for me, the blooming of any Petrocosmea is a thrilling event, however, this one is a particularly special event. P. parryorum has always been a tough species to flower in my conditions. I've never figured out why. Others bloom it easily, but that is certainly not the case for most of us. So, last week, when those first few flowers started to open, I began to check my plant several times a day, in anticipation of it's coming into full flower. The time has arrived!

When researching P. parryorum, one of the first things I noted was that it was not listed in the Flora of China....then it hit me. P. parryorum is not FROM China, so that is probably why. P. parryorum was found in India and Burma by Cecil Ernest Claude Fischer (usually written C.E.C. Fisch.) in 1926. I have been unable to find much more than that on either the plant or the man Mr. Fischer. The plant, was not listed by Craib in his first revision of the genus done in 1919, because it was not known then either. So, one is left with the scant information in Wang's Second revision of the genus done in 1926, where it is called the "Indo-Burma Petrocosmea". It is placed by Wang in Section Anisochilus, noted for the top two petals of the corolla being approximately one half the length of the lower lip of the corolla...which they are.

Scant information, however, does not diminish the beauty of the plant in my eyes. It is a favorite plant for me. This species is often maligned by judges when it is entered in the "not in flower" classes for being "just a plain green plant". I would argue that it is green and it is a plant, but it is far from plain if one takes the time to know it. All parts of the plant are densely covered in long silvery hairs that give the plant a "frosted" or silvery appearance in the correct light. These hairs are often more golden in color near the base of the plant of the base of the petiole. The leaf surface is pebbly and the leaf is heart-shaped. If given proper culture and good light, the plant can be quite attractive. But the event of it's flowering is wonderful. Tight clusters of buds emerge from the crown of the plant to unfold into silvery furry clusters of lavendar flowers. The color of the flowers against the silvery hairs is lovely indeed, a feast for these Petrocosmea enthusiast's eyes!

A cluster of P. parryorum flowers emerging from the silvery, hairy crown of the plant....

This photo, by Julie Mavity-Hudson, shows the many attributes of P. parryorum...the glossy sheen of the pebbly leaf surface. The silvery hairs grab the light to give the plant a "frosted" appearance.

So, how did I get it to bloom? P. parryorum has been in my collection for about ten years...maybe more. It has only bloomed twice...last year with one spike of five flowers and this year, when it has more than a dozen inflorescences with multiple buds on each. I am not sure what I did differently. I grew the plant enclosed under humidity domes, for the past two years...which I have never done before. Also, I used to repot Pets about twice a year. And I never let the plant get very large before I would restart it as a leaf cutting and grow a new plant. I was in my African violet period then and thought that frequent repotting was the way to go....for Petrocosmeas, I am now convinced it IS NOT the way to go. My Petrocosmeas that I have allowed to remain in the same pot for four or five years now definitely perform best. I am now convinced that allowing Pets to mature is a secret to success. My plant is in a 5 inch pan pot where it has remained for four years now. It is quite rootbound. I remove the top of the soil about twice a year and place fresh soil with systemic pesticide granules mixed in. This is the only pest control that I use and I have never seen any insects on my plants. It grow it in the basement of my home, where temperatures the past two winters have gotten down to 38 degrees F. The Petrocosmeas loved it. I keep many of them enclosed under humidity domes and the ambient humidity in the room is usually greater than 50%. I allow P. parryorum to dry out at the root a bit between waterings. I use a variety of liquid fertilizers and alternate them at random. I fertilize about twice a month. Light on the shelf where P. parryorum grows is quite dim by most light gardener's standards. The plant sits below two tubes of light at a distance of about 16" from the leaf surface to the light fixture.

I had hoped to take photos of the mature plant in flower, however I dropped the plant while cleaning the shelves and broke off many of the leaves. That was not a good day to say the least, but the plant seems to have suffered no ill effects other than being mis-shapen and bruised. I am already attempting to make crosses using P. parryorum.

So if you haven't tried P. parryorum, you must! But be patient. It is worth the persistence and the wait.

Petrocosmea nervosa and sp. 'vittatae' - Are they the same species?

Petrocosmea sp. 'vittatae', sometime distributed as P. vittatae, is obviously a close relative, if not the same species as P. nervosa. P. vittatae is not a valid species name.




I have always had a special fondness for Petrocomea nervosa. It was one of the earliest Pets that I learned to grow and it never fails to bloom faithfully and heavily for me every year. The grey, silvery hairy foliage crowned with a mass of blue flowers never fails to make me feel happy when I look at it. My three plants of P. nervosa are all putting on their best show for me right now.

One of my happy P. nervosa plants in bloom today. Notice the offsets near the center crown.

Petrocosmea nervosa flower.

The upper petals being nearly the same length as the three lower petals is one of the characteristics that places P. nervosa within Section Petrocosmea of the genus Petrocosmea. This section is believed by some taxonomists to contain the most primitive species within the genus based on flower structure and the configuration of the anthers. As morphologically similar plant labeled P. vittatae was introduced into cultivation a few years ago. The late Maryjane Evans spent much effort researching the origins of the new plant material as well as the name P. vittatae and found nothing. The person who gave the plant to her could not recall from whom they had originally gotten the plant, and the species P. vittatae is not a valid published species within the genus. I have noted that P. sp. 'vittatae' grows larger and has leaves of heavier substance, and substantially larger in size than P. nervosa, when grown side by side with uniform culture. Both plants offset heavily as they approach maturity and tend to only flower once they have produced offsets. The flowers of both plants are identical in every way for me in my conditions and the plants bloom at the same time. If shown a leaf, though, I can usually tell which leaf is 'vittatae' and which is nervosa, due to the larger size and thicker, heavier substance. I find that sp. 'vittatae' matures a little faster than nervosa in my conditions and tends to produce plantlets from leaf cuttings faster than nervosa.

P. sp. 'vittatae' on the left and P. nervosa on the right. Both of these plants were grown side by side in the same tray on my light stands and were taken from leaf cuttings put down to root on the same day. They are shown in five inch pan pots.

P. sp. 'vittatae' growing on my lightstand. From this photo, one can see that I grow this species with quite dim artificial light. Note the offsets...this species and P. nervosa bloom for me only once they have produced offsets.

I grow both species in quite dim light. SHALLOW pots...a must!, an I keep soil evenly moist with occasional short periods where I allow it to dry a bit. I find that these species are a bit more succulent than some others and prefer soil a bit drier. Once potted in a five inch pan pot, I leave them there for several years as long as they are happy and healthy. I find that they bloom most heavily when not disturbed and allowed to mature and get a bit rootbound. I remove a thin layer of soil once a year and replace it with fresh medium containing systemic pestacide granules. I have never been troubled with insects with this treatment and my plants seem happy.

SO, what do you do if you have P. vittatae? First, keep it if you like it. A few years ago, once it was announced that research had found no such species as P. vittatae, some experienced Pet purists were saying that any plant labeled "P. vittatae" should be thrown away and NOT distributed as there was "no P. vittatae". My feeling is that it IS a Petrocosmea, and it IS a slightly different plant than P. nervosa...so we should continue to grow it and keep the plant labeled as something new and different. I changed my labeling from P. vittatae to P. species 'vittatae'...in order to designate that it is a species that is unidentified and was given a cultivar name of 'vittatae'. Whether that is right or wrong, it allows me to keep it seperately labeled in my collection and it continues to adorn my home and enrich my life with it's beauty....regardless of it's name. You know....."A rose by any other name.........."

Petrocosmea xingyiensis - A New Species Described!

Thanks to my friend Jaco Truter for informing me of the publication of a newly described Petrocosmea species from China -- Petrocosmea xingyiensis! Published in the June 18, 2009 edition of Novon, the species is described by Yi-Gang Wei and Fang Wen. You may find the description here: hua.huh.harvard.edu/china/novon/novo-19-02-261.pdf

The authors place this new species in Section Anisochilus ser. Iodioides. The plant was collected near Ghizhou Province, in the Maling Gorge, Xingyi County, Southwestern China on 7 Oct. 1998 from cliffs of limestone rock or along the Qingshuihe River at 930-1000 meters elevation. The population was believed to be less than 330 individuals in the habitat and is listed on China's Red List of endangered species. An article I read on this area states that the State is building a dam which is expected to flood the Gorge and destroy much of the habitat. It is indeed sad to think that this lovely new species could be lost to us if it is not already. We may be about to lose this species just as we are learning of it's existence.

An Overview of Petrocosmea - To Know Them Is To Love Them

One of my favorite Chinese proverbs states that when someone shares something of value with us, we have an obligation to pass it on to someone else. I think that sums up my reason for starting this blog....

When my interest in knowing more about Petrocosmea first began, I found it extremely difficult to find information about the genus, and even more difficult to find information on proper culture of the plants. It is my hope, that in writing about what I have learned, and continue to learn about the genus as I continue to study it, that others who want to know more and grow Petrocosmea more successfully will find the information helpful.

So, I thought with this post, I would review the genus as a whole.

The genus Petrocosmea was first described in 1887 from Dr. Augustin Henry's Ichang collections by Daniel Oliver when he described the species P. sinensis from western Hubei, which is a province in central China, near the Yangtze River. In 1919, William Craib wrote the First Revision of the Genus Petrocosmea. No further revisions were done until Wang Wencai did the Second Revision in 1985. The genus includes three sections: Section Petrocosmea, Section Anisochilus, and Section Dienanthera. Among the three sections, the total described species in the 1985 revision is 27 known species and 4 varieties. A 28th species...P. formosa, was described by B.L. Burtt in 1998. The name Petrocosmea comes from the Greek words for "pretty" and "rock". The chromosome count for Petrocosmea is 34.


The geographical distribution of the 28 species contained in the genus includes 24 species and 4 varieties from Western and Central China, with the remainder found in Myanmar (Burma), Thailand, NE India and S. Vietnam. The species are often found in very restricted locations, in forests, growing among limestone rocks at elevations from 300 - 3200 meters. This elevation is typically cool to rather cold in temperature. Humidity is generally high due to mists at these elevations, and the locations are often near streams. The species are often found on only one or two mountain tops or on one or two islands.

The center of the rosette of P. sericea. I really like the cupping of the leaves on this furry species! It is one of the slowest growers of the genus, at least in my conditions.

The first Section described was Section Petrocosmea, which includes the species considered to be the most primitive of the genus. This section of genus contains seven species and one variety. One of the distinguishing features of the species in this section is that the upper lip of the corolla is nearly equal to the lower lip of the corolla. It contains the species P. flaccida, P. nervosa, and P. grandiflora. Examine the flowers of these species, and it will be apparent that the upper petals and the lower petals are very nearly the same length.

The flower of P. duclouxii, which I suspect may actually be P. grandiflora. This plant has also been distributed as P. floribunda, a species name that is invalid.

The second Section described is Section Anisochilus, the largest section, containing 16 species and two varieties. P. parryorum is a commonly grown species found within this section. One distinguishing feature of the species within this section is that the corolla upper lip is half the length of the lower lip. This section also includes P. barbata, P. rosettifolia, and P. forrestii

The flower of P. rosettifolia #1.

The foliage of P. rosettifolia #3. The lovely yellow veining along the central and lateral veins is passed along in hybridizing to the progeny....something I was happy to discover!


The third section within the genus is the last to be described, being added by Wang during his revision of the genus in 1985..Section Dienanthera. The flowers of this section have a uniquely different pollination mechanism from the other two sections. The anthers are constricted below the apex to form a short "beak" that actually ejects the pollen from the tip of the beak when pressure is applied to the base of the beak. P. formosa is a species found within this section along with P. kerrii. The species within this section often have a rather large leaf blades with longer peduncles.

So, as your Pets come into flower this season. Take the time to examine the individual flowers up close. I have learned a lot about the genus by examining the flowers. I am often asked if I know the natural pollinators of Petrocosmea. I do not. I have been unable to find any information or even speculation on how the flowers are pollinated in nature. If anyone know, please let me know!

The "Petrocosmea Lady" - People Who Inspire Us...

We're having another rainy day in Pittsburgh today, and I traveled to my basement upon arising this morning, to find some sunshine under the lights. As I looked around, I decided to pick a bouquet of my favorite flowers to bring upstairs for my desk, where I knew, later in the day, I had to get some work done. As I realized how great it is to have enough Petrocosmeas to be able to pick a bouquet of them, I began to think back to how my journey of love with these simple little purple flowers began. And when I think of Petrocosmeas, I always think of one person in particular....Mary Bozoian.

It is important to have people in our lives who inspire us. Mary has been just such a person for me in my devotion to knowing all that I can learn about Pets, and growing Petrocosmeas more skillfully. In 1998, when I first stumbled across a photograph of a Petrocosmea, I was immediately fascinated with them. In trying to learn more about them, I was led to the American Gloxinia and Gesneriad Society, now "the Gesneriad Society". And, in referencing Petrocosmeas there, one name kept coming up in association with them.... Mary Bozoian. Everytime one was listed, it was always noted as being grown by Mary. When reading about the annual Conventions, and all fo the exciting new species being introduced and offered in the auctions...again, Mary Bozoian was the person attributed to the Pets. Mary was "the Petrocosmea lady". So, in 2000, when I traveled to Tampa, FL for my first convention, I had to see for myself who this person was. What a delight it was to finally meet Mary!

Me, with my hero the "Petrocosmea Lady", Mary Bozoian at the Gesneriad Society Convention in Silver Spring, MD this past July.

Meeting Mary for the first time, I found her to be a warm, gentle soul with a giving nature. She was generous with her knowledge, and her plants, and we became great friends. When I returned home from that convention, I was honored to receive a box containing several Petrocosmea species, all tenderly wrapped and labeled, and of course, expertly grown. I still have those same plants in my collection nearly ten years later. I was struck by how warm and generous Mary was with a newby such as myself, and by how patient she was with my thousands of questions about growing Petrocosmeas. Over the next couple of years, Mary gave me lots of hints and instructions during the many phonecalls we shared to keep in touch.

A plant of Petrocosmea forrestii, propagated from the original plant sent to me by Mary Bozoian in 2000. I entered the plant in convention this year, and have used it as a parent in many of my hybrid crosses.

Seedpods forming last year on P. forrestii, a plant given to me nine years ago by Mary. It turned out to be a prolific pod parent in a number of my hybrids last year.

Mary provided much inspiration to me over the years. She always enters immaculately grown show plants and was almost always the first person to enter a new Petrocosmea species in a show. I always try to follow her example whenever I enter a plant for show....especially if it is a Petrocosmea. Mary grows her plants in her basement. Basements often offer ideal conditions for gesneriads as they are often cool and more humid than the rest of the house. Gesneriads that prefer cooler conditions, such as Streptocarpus, Chirita, alpines, and Petrocosmea often thrive in a basement. I grow most of my Pets in my basement, where they are quite happy, but find that they do fine upstairs too.

A tray of seedlings on my basement lightstands, a cross between P. forrestii and P. duclouxii. Several of these are forming buds now! The foliage on these is exceptionally soft and furry. I always have to touch them when I am in the plant room.....

Ten years later, the inspiration and encouragement, not to mention the plants, that Mary provided, continues to fuel my love of Petrocosmea. It is important to have heros and inspirational people in our lives, particularly with regard to our hobbies and passions. I got the opportunity this past July to visit again with Mary and her daughter, and to thank her for the passion for learning about Petrocosmeas that she inspired in me. Gesneriad devotees are wonderful people, as are plant people in general. The generosity of these people with their time, their knowledge, their plants, and their friendship touches many peoples lives and betters them in the process. The best tribute I feel we can make for such people is to continue to share our plants and our knowledge with those who are new to our hobby. I hope all of you have a "Mary Bozoian"... AND a Petrocosmea, in your lives.

Double the Fun!! The Apperance of Double Flowered Petrocosmeas

I will always remember the day when I first saw a photograph of Nagahide Nakayama's new hybrid. At that time, he was calling it cultivar 25 or 'cv25', it did not have a proper name yet. But, it's outstanding new qualities were remarkable, even in the photograph. For a Petrocosmea fanatic such as myself, this was a red letter day!

Through the generosity of a friend, I soon had a couple of leaves of this magnificent new Pet in my propagation boxes. So, it was different, and new, and beautiful, but as a budding hybridizer (no pun intended), I was curious about how it came about. Where did the trait towards double flowers come from? Certainly there were no double flowered Petrocosmeas to work with. As my hybridizing has progressed, one of the most exciting realities to come to light is that the genus Petrocosmea appears to have a great tendency toward mutation and variation in it's genetic pool. Working with the seedlings produced from crosses between two species is proving to produce a wide range of variation every time...at least so far.

Well, that beautiful new hybrid recently received a proper name...Petrocosmea 'Imperial Butterflies'...and the grandeur implied in the name fits the plant! As the picture above demonstrates, it does produce double flowers. Those few that are not fully double have extra petals and ruffling of the petal margins. I am most anxious to incorporate this plant into my hybridizing program.

A flower of P. 'Imperial Butterflies' with 12 petals...more than double the normal number of 5 petals. Flowers are large for a Petrocosmea, and are a rich purple color. Flowers are also longlasting on the plant.

A sibling of 'Imperial Butterflies' is the new hybrid 'Asa Blue'. P. 'Asa Blue' produces a large number of large five petaled flowers. I was thrilled last year, when a cross utilizing P. 'Asa Blue' set seeds. The cross used pollen from P. begoniifolia. Over the past two months, those seedlings have begun to flower. I am growing out 27 seedlings at the moment. Out of the seven that have bloomed so far....... I got one double!!!! Pictured below, this seedling produces double flowers, that have the extra petals coming out of the center of the flower. This appears to be a different mechanism for doubling than I see in 'Imperial Butterflies, which produces extra petals within the outer corolla of petals. Often, with 'Imperial Butterflies' the buds appear to be two fused buds, forming a flower out of 'two buds', whereas my seedling forms a normal, or typical bud, with the extra petals in a tuft in the center of the outer corolla. Regardless of how and why, I am thrilled to have this plant among the seedlings. Petals on the seedling are shorter and rounder, similar to the begoniifolia parent, with a white center to the flower as if they are being lit from within the calyx. The plant has now produced eight flowers and all have had extra petals in the center.

The flowers appear to often be missing the anthers or the anthers are deformed or tiny. Perhaps the anthers are being transformed into the extra petals?

My seedling...the result of a cross between P. 'Asa Blue' and begoniifolia. So far, all flowers on this plant have been doubles.

I was a great day when I first saw these buds open and realized they were doubles! Hybridizing Petrocosmeas is turning out to be a wonderful adventure!

Two siblings....P. 'Asa Blue' on the left, and the double flowered P. 'Imperial Butterflies' on the right. Both the result of a remake of the cross that produced P. 'Momo' many years ago.... P. nervosa x flaccida. Note the differences if the habit of these two siblings.

So the future of Petrocosmea hybridizing appears bright and exciting at the moment. I feel this must be a taste of what the early hybridizers of Saintpaulia must have experienced when African Violet hybridizing was in it's infancy. Do you think I can get my double seedling to cross with 'Imperial Butterflies'??????

Zippers and Offsets - Problems Affecting Symmetry in Petrocosmeas

I was happy, and relieved at a recent Gesneriad Society show, to see that the judges has given a blue ribbon to a Petrocosmea that had "zippered". Zippering is a term sometimes applied to a phenomenon seen among some Pet species as they mature, where the normal circular central growth point begins to elongate and become linear, creating the appearance of a "zipper" down the center of the plant. It is often felt that this ruins the symmetry of the plant, which we've come to expect, and perhaps even demand be a perfect, symmetrical circular rosette of leaves. I have heard judges comment that they "don't like" this appearance, however it is "what the plant does", and therefore should not be penalized substantially, when judging.



A plant of Petrocosmea 'Short'nin' Bread' that has "zippered", causing the central growth point to elongate. P. 'Short'nin' Bread' is a hybrid between P. flaccida and P. forrestii. P. forrestii is prone to zippering, and is likely the reason this hybrid is also prone to this phenomenon.

A plant of P. 'Short'nin' Bread' showing the more typical, and aesthetically pleasing round growth point in the center. With maturity, this plant could still go on to zipper.

Zippering is one of those qualities that is not common among all Petrocosmea species but is typical of a few. Those species that are prone to zippering are P. rosettifolia P. forrestii, and P. species 'China-2005'. One of the goals of my hybridizing program is to select cultivars that are free of this trait. This will require growing the plants until they are mature up to three or four years of age, as this trait does not often show up until the plants are a few years old. P. forrestii is a prolific parent for me, and I have used it in a number of crosses, so these will have to be evaluated for a while in order to check them for this trait. As P. forrestii contributes a smaller plant size, floriferousness, and a pleasing leaf shape and rosette shape to it's progeny, it is still worthwhile to utilize the species as a parent in spite of the tendency to zipper.

Why plants zipper is a mystery, however, I have a theory. As the zipppered plants continue to mature, they bloom much more heavily and will eventually form multiple crowns, which will eventually seperate on their own and become seperate plants. I feel that zippering may be an evolutionary tactic to increase the species by forming new plants as the crowns seperate, and perhaps, with the heavy flowering, making the plant more likely to produce more seed for propagation of the species. Of course, I have not idea if any of this is true, but it is my own theory of why this might happen in some species.

An example of a plant that never zippers for me ( at least it hasn't yet on my seven year old plants). Petrocosmea sericea forms and maintains a beautiful symmetrical flat round rosette.

Another bothersome habit of some Petrocosmea species is that of abundant offset production. As some plants mature, and near flowering size, the flat round rosette suddenly will begin to become "crumpled" and the orderly leaf arrangement becomes jumbled and messy. Soon after, offsets can be seen enlarging underneath the leaf crown. As they mature, the plant begins to look more like a mass of jumbled leaves. This ruins the symmetry of a plant that might otherwise have been a perfect showplant. Of course, the offsets can be removed and rooted for instant plants, or left on the plant if a flat rosette is not that important to you. The offsets will bloom too, creating a large mass of flowers .

A four-year-old plant of P. rosettifolia #3, in a five inch pan pot, showing this year's crop of offsets. I have chosen to leave them on the plant to let it mature and see what continues to happen. Offset production seems to be triggered by stressing the plant from underwatering or as the plant nears flowering size.

Again, offset production is a problem from the standpoint of selecting future showplants. It is another trait I have chosen to select against in my hybridizing program. Species prone to offset production are P. nervosa, P. flaccida, P. barbata, P. rosettifolia, P. sp. 'China-2005', and P. forrestii. P. duclouxii and P. sp. 'Yumebutai' have been rare producers of one or two offsets per plant. P. minor, P. sericea, and P. begoniifolia have never produced offsets for me in my conditions.

A three year old plant of P. forrestii showing a splitting of the crown into three seperate crowns. This particular plant did not zipper, but just formed three crowns. As the plant continued to mature, these three crowns eventually "fell apart" in the pot and continued to grow as seperate crowns. This plant flowered very heavily, with in excess of two hundred flowers produced last season.

Since most Petrocosmeas entered in shows are entered "not in flower", as foliage plants, the plants must have a high degree of ornamental value to score well. Ornamental value, to many judges, seems to demand a Petrocosmea have a perfectly round, flat rosette, with the leaves arranged in an orderly spiral extending out from a single crown in the center of the plant. Again, this is most, but not all judges. Therefore, I feel that selection of clones and new hybrid cultivars that maintain a rosette free of offsets and zippering is a trait hybridizers should be striving for.

Petrocosmea flaccida - A New Clone !

Petrocosmea flaccida 'ABG 1990-1581' - a dainty new addition to cultivation!

I was pleased during a visit to the Atlanta Botanic Garden in June, 2005, to find that they had in cultivation a new collection of P. flaccida. As I've said before, new Petrocosmeas always create a stir, so I'm sure my excitement was evident to my friend Mike Wenzel, who was patiently showing me around. At the conclusion of my visit, he was gracious enough to offer me a couple of leaves. Now, I treasure it in my collection.

As for the history lesson, ......Petrocosmea flaccida is often one of the first Pets that many of us started out with. It's name refers to the flaccidity of the soft, silvery leaves. P. flaccida was first described by Craib in 1919, having been collected in Muli, Southwestern Sichuan, and near Yongning, in northwestern Yunnan Provinces in China. Plants were found "growing on rocks in thickets, 1830-3,000 meters above sea level." It is grouped within Section: Petrocosmea of the genus, which as of the second revision of the genus done by Wang in 1985, included only 4 species and one variety. P. nervosa, another of the older Pets in cultivation, is also contained within Section : Petrocosmea.

The "traditional form" of Petrocosmea flaccida, which I have grown for a number of years. This plant is growing in a four inch pan pot and is approximately six inches in diameter.

My "traditional" P. flaccida, which I've spent many years with now, grows significantly larger than this new form. The leaves on my P. flaccida are more cordate in shape, and are nearly three times as large in diameter as the dainty little leaves on the new one. The flowers are darker on my older form, larger, and have two prominent white dots at the base of the lower petals on either side of the opening of the throat. The new form does not have these dots.

The new P. flaccida 'ABG 1990-1581' is much smaller in all regards. Leaves have a rounder shape, and are only about one third the diameter of the regular P. flaccida's leaves. This plant is in a three ounce condiment cup and the whole plant is less than four inches in diameter. I tiny little plant....

A photo showing both forms of P. flaccida in my collection. These plants were grown side by side on my light shelves and had uniform culture. Both plants are in their second year of growth and second flowering season.

A well grown P. flaccida exhibited in the Gesneriad Society Convention in Silver Spring, MD this past July.

Having a new collection of P. flaccida is exciting for several reasons. First, it is great to have now genes available, as most P. flaccidas are likely just propagations from a few original plants. The new form also offers an exciting option for hybridizers (like me). One of my goals in hybridizing Petrocosmea is to create miniature Petrocosmea. I have a couple of promising tiny Pets and this new P. flaccida, with it's small stature, will definately be involved in some hybridizing efforts this year! As for growth and culture, it definately needs a smaller pot. Placing this plant in a four or five inch pot would likely result in the loss of the plant due to root rot, and would be of no benefit as I doubt it would ever need such a large pot. Otherwise, I grow it exactly as I do my other Pets. I have noticed that it is painfully slow to propagate, but if one is patient, it is easy to prop. It is just going to take a while for it to reach a decent size.

I began distributing leaves and plants this year at the Gesneriad Society convention, so hopefully, within a few years, this new form of our old friend will make it's way into more homes!

Two New Hybrids from Japan

Petrocosmea 'Asa Blue' - a new hybrid with lots of flower power!


New Petrocosmeas always create quite a stir among those who admire and collect them. The genus has proven very difficult to hybridize, so a new hybrid is really exciting. For over a decade, we had only one hybrid Petrocosmea....P. 'Momo', a hybrid between the species P. flaccida and P. nervosa. This hybrid was made by a gentleman from Japan named Nagahide Nakayama and was named for his wife. Now, after many years, he has remade the same cross, and the remake has produced two promising introductions...P. 'Asa Blue' and P. 'Imperial Butterflies'.

I am often asked how I get my new Pets. The answer is that almost every time, they were given to me by a friend. That was the case with these two hybrids when last fall, a friend sent me leaves of both of these beauties. Even as leaves, I could see a lot of differences in the two plants. As they have matured, the differences are dramatic and exciting. It's hard to believe that they came from the same seedpod.

P. 'Asa Blue' looks very much like 'Momo' with a couple of exceptions. The flowers are different, lighter blue and more numerous. This plant really blooms heavily and at an early age. It has proven easy to grow. It was selected by Mr. Nakayama due to its very heavy flowering habit.

P. 'Imperial Butterflies' is a real breakthrough for Pets. It is a much heavier plant in all respects. Leaves have a heavier substance, a slightly serrated edge to the leaves, and the leaves are rounder and larger. But, it is the flowers that are such a knock-out. For starters, they are "double" and have pronounced ruffling of the petals. The color is a darker purple than 'Asa Blue' and the calyx lobes at the base of the flowers have fingers along the edges, giving them a feathery appearance. The flowers often have 10-12 petals, which is more than double the usual number of five petals for a Pet flower. It too, blooms heavily, and the buds appear very early, and the base of each leaf, looking like little grean pearls lying on each leaf. A spectacular "must have" Petrocosmea if you are a fan.

As often happens with hybrids, the flowers of 'Asa Blue' are significantly larger than the flowers of either of it's parents.

Even as a young plant in a three inch pot, P. 'Imperial Butterflies' is a great plant. Every flower is ruffled and has extra petals.

Petrocosmea hybridizing, while in it's infancy, is proving to reveal a surprising amount of variation in the seedlings from the same seedpod. This high degree of variation among the progeny of a single cross gives exciting promise for the future of the genus and those who adore Pets. This photo shows the distinct differences between 'Asa Blue' and 'Imperial Butterflies'...two siblings from the same cross. These two plants are exactly the same age and were grown side by side on the light shelf with uniform culture.

Note: P. 'Imperial Butterflies' was orginally distributed with the cultivare name 'CV-25'. If you have the plant under that name, change the label to 'Imperial Butterflies'.

Tim