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