A Weekend With Petrocosmea

Autumn is my favorite season. Here in the northeast, it can be a spectacularly beautiful time as the trees and shrubs outdoors begin to show vivid colors. The blue sky outside my front door is framed with the most brilliant golden yellow leaves of the maples in all directions. While cooler weather and fall color marks the end of the growing season for the gardens outside, for Pet lovers, it marks the beginning of the heaviest period of bloom for many of the species. This autumn has been a beautiful one and a busy one, so far.

The photo above is a scene from Lewiston, NY, on Goat Island at Niagara Falls. This past weekend, I was priveleged to spend an entire weekend studying Petrocosmea genetics! (with a brief side trip to "the Falls". ) I must keep you in suspence a bit longer, but we are getting some interesting data on the interspecific relationships of the Petrocosmea species we have in cultivation at this time. This information will hopefully contribute some valuable data to our knowledge of this fascinating genus that is still largely unstudied. Of course, the taxonomic component still needs a lot of work, and we are slowly but surely working on that too.

Having access to a microscope allowed me to spend some time studying the anatomical and structural characteristics of Pet species. I could spend months just looking down those lens and gazing at the minute, and miraculous features of each species. Above are some quick, ten-minute sketches I drew of the anthers and filaments of P. nervosa and P. minor-smooth leaf form. The pollen is stored within two "pillow-like" cavities on either side of the mid-line of each anther. The pollen "shoots" out of an opening at the tip (pointed area) when pressure is applied to the "pillow". The shape of the anthers is one of the features that determines species' placement within the three Sections of the genus Petrocosmea. The more rounded shape of the tip of the anther of P. nervosa place it in the most primitive section..Section : Petrocosmea. The pointed tip of the anther of P. minor "likely" places it in Section : Anisochilus (that is my guess). The filaments of P. minor were thick and globular, with a white apex and deep blackish purple violet base. The tiny hairs on the filament were white, with purple tips on the white apex.....the pigments in the filament looked like little purple jewels under the microscope. Amazing and very beautiful!!!

As you can see from the drawing above, two things are evident. First, I am NOT an artist!! and second, there is much to learn from the differences in the anatomical structures of Petrocosmea. I hope to spend much more time in the next few months attempting to iron some of the mysteries and frustrations with the mis-labeling of species and perhaps even confirm that we have some unidentified (undescribed) species within our collections! For me, sketching and drawing the floral parts allows me to focus on every minuted detail. It is a trick I learned as a nursing student many years ago. As I draw, I notice things that I had never noticed before. Try it with your own Pets when they flower. Remove a leaf or a peduncle and spend a few minuted dissecting the structures and studying them. You'll gain a renewed appreciation for the miracles of nature and Petrocosmea!

Excitement continues in the plant room with all of the seedlings coming into first flower. The latest seedling to flower from the cross P. 'Asa Blue' x begoniifolia. Again, something new! This flower has some reddish and pinkish pigment. Note the reddish pigment in the upper petals near the base and at the base of the throat. (The picture doesn't do it justice!). This flower is quite large...the largest so far, and the petals are very broad and rounded with an unusual "serration" along the margin (I have no idea where that came from??!!) A different shape than any of the Pets we have so far. While the plant is still tiny, it is putting out a great number of buds.

The new seedling, (left) with a sibling (right...the more typical shape so far), to show the different shape of the new flower. The flower is large, and the peduncle is nice and short, and strong. This one has a lighter pinkish color also, sort of mauve in color. It definately deserves to be kept for further evaluation. Foliage has a nice purple band around the edge...as can be seen in this photo.

Photo of P. nervosa in flower. I love this species. The blue flowers floating above the silvery leaves.

One last comment that I keep getting lots of questions via email about. Shallow pots. Let me just say, if you are struggling with growing Petrocosmea....my first bit of advice is always... "Shallow pots, shallow pots, shallow pots!!!". Once after giving a talk where I had just advocated and preached the virtues of using shallow pots for Petrocosmea culture, a lady came up and proudly announced that she NEVER used shallow pots and her Petrocosmeas won awards all the time in standard pots. She was quite proud of herself and her Petrocosmeas and wanted to let me know that I was mistaken. It was a fun conversation and I got a chuckle out of it. YES, Petrocosmea can be grown very well in standard pots. I'm sure prize-winning specimens could be grown in pots three feet deep if one wanted to adjust culture to accomodate this. But, in my experience, shallow pots prevent a lot of extra effort and disappointment from root rot when the large volume of soil results in soil staying damp for too long. Shallow pots, allow more air to get to the roots, more horizontal room for the shallow and wide root system to roam and great evaporative surface area to increase humidity, keep roots cool, and again, allow soil to dry quickly after watering. They just work better for me. I've used them in the humid and hot south of the USA, the mountains of West Virginia, and now the cooler climate here in Pennsylvania. I use them in windowsill culture and under lights, with top watering, bottom watering, mat watering and wick watering, all with better results than I get from a taller, deeper, narrower standard pot. And, the plants seem to shape up better, with nicer symmetry with the wider diameter of the shallow pots or "pans" as they are usually called. But, to answer the question I keep getting, YES, Pets can be grown quite successfully in standard pots as long as one is cautious of the potential for root rot. As for me, I'll use shallow pots.

Tribute to a Lovely Lady - P. 'Rosemary Platz'

The flower of Petrocosmea 'Rosemary Platz', my first hybrid. The flower shows the influence of both parents. A lovely sky blue from P. sericea, with the yellow in throat from P. rosettifolia #3.



Friends are among the dearest of all things in our lives. My love of gesneriads has afforded me the opportunity to meet so many wonderful people who share my fondness for these plants and I now count many of those people among my best friends. When my first hybrid Petrocosmea flowered a couple of years ago, I knew exactly who I wanted to honor with the naming of the first selection. Rosemary Platz is one of those spirited, energetic people who makes anyone she meets feel good. Her smile is bright and constant, and her laughter is infectious. A beautiful person, inside and out, she always wants to learn more about gesneriads, and she is an accomplished grower, a master judge, and skilled designer in gesneriad shows. I am honored to call her my friend.

My dear friend, Rosemary, at the annual convention of the Gesneriad Society last July.

P. rosettifolia #3 was the seed parent from my hybrid. This form has the eye-catching yellow patterning along the central veins of the dark green glossy leaves. Seedpods took 67 days to ripen. The cross produced pods with large quantities of seeds and excellent germination.

The pollen parent, P. sericea. This species contributed the pleasing lavendar coloration to the flower, as well as it's size and form. A reciprocal cross using P. sericea as the pod parent produced few seeds, from which only two plants have survived.

My original plant of P. 'Rosemary Platz' is now coming into flower for it's third bloom cycle. Each time it flowers, I am reminded of my friend, and it's namesake. (As it comes into flower, I will post a photo of the whole plant, showing the foliage.) It has proven, so far, to be an easy plant to grow. It shapes well for show, and has so far, had no problems with disease or insects. Leaves are glossy and show the best qualities of both parents. In a five inch pot, my plant is maintaining a diameter of about six inches and it has more flowers each time it blooms, as it gains more maturity. It propogates easily from leaves and the plantlets grow quickly and flower at an early age, usually about five or six months. I've been pleased with it. The name was registered with the Gesneriad Society last January. It marks the first time either species has been used in hybridization.

In Bloom Today...The "White" Petrocosmeas

The clean, white flowers of Petrocosmea begoniifolia at are a lovely contrast to the dark green, purple-backed leaves that this plant bears. The purple of the leaves is carried into the pedicel and calyx, as can be seen here. The flower also has two lemon yellow splashes and has a more cup shaped corolla than most Pet species.



Although white flowers in the genus Petrocosmea are among the minority, it occured to me this morning as I tended my beloved Pets that all of my white-flowered species are in flower now. I've always been partial to white flowers, any white flower...gardenias, magnolias, white roses....and the white flowered Pets are also among my favorites. So, I thought I would take advantage of natures gifts to post an entry about the white flowered Pets I grow.



Petrocosmea kerrii boasts white flowers with yellow highlights, much like P. begoniifolia, however, the yellow highlights on P. kerrii are uniquely on the top petals or "roof" of the throat, rather than the "floor" of the throat. Now, I have to see if I can cross P. kerrii with begoniifolia and get flowers with yellow on both the top and bottom petals??!!!




It was interesting to me, to note that ALL white-flowered species have yellow in the flowers....something that is rarely ever noted in the blue flowered species. The yellow is usually found on the lower petals....with the exception of P. kerrii. P. kerrii is placed within Section Dienanthera of the genus, where a yellow blotch on the upper petals is a characteristic of the species within this section. (P. formosa, which has lavendar flowers is also placed within the Section, and it too, has yellow on the upper petals. ) By crossing the white-flowered species (with yellow in the lower petals) and the blue-flowered species (with no yellow in the flower), I have been able to get some yellow in purple flowers on the hybrids.


The Petrocosmea rosettifolia group (I have at least four different forms of P.rosettifolia), generally has lavendar flowers, with the exception of one form which I received labeled P. sp. 'G25KC00'. I have since labeled it P. rosettifolia #3. This form is the only one with white flowers. I used this form in my first hybrid - P. rosettifolia x sericea and got one white flowered seedling which also happened to be a miniature sized plant. I named that hybrid P. 'Keystone's Bantam'. All of the other seedlings from that cross have been lavendar, so far, however, I have about twenty more to flower this year, so I may still get some new white forms.

The white-flowered form of P. rosettifolia which I labeled #3 in my collection in order to identify it seperately from the other three forms that I have. This form also has three bracts on the cyme, and the flowers have a heavier substance and larger size than the other forms of the species that I grow. The cymes are also larger in diameter and grow taller.

The dainty little charmer, P. barbata has flowers that almost always open white and stay white until the wither. For others, these same plants produce lavendar flowers, so P. barbata may not truly be "white flowered", and the trait may be cultural or environmental. It has the smallest and most fragile, thin flowers of any of the Pet species, for me. A heavy bloomer that is often among the very first species to bloom as Pet season approaches each autumn. One other thing of interest with this species is the fact that it tends to have a "semi-dormancy" after flowering where the outer leaves are dropped and only a tightly cupped center "button" of green leaves remains, until spring approaches, when the plant once again, springs into growth.

Petrocosmea 'Keystone's Bantam'--- My only white-flowered seedling from among about forty seedlings that I have flowered, so far. The happy result from my first hybrid cross P. rosettifolia #3 x sericea. This seedling was tiny from the very beginning and has never exceeded three inches in diameter, even after three years of growth on the original plant. Flowers are large for the size of the plant, and are purest white, with NO yellow! The flowers on this seedling resemble the flowers of the rosettifolia parent, pictured above, most closely, while the flowers on all of it's siblings have favored the sericea parent more. The little plant originally had an "odd" center that resembled a little furry button, (note this in the photo above), however, the plant grew out of this and now this same plant has a "normal" center of tiny leaves. The plant above is in a two inch pot. Potting it into a larger pot did not result in a larger plant. Leaves are a little more reluctanct to produce babies than it's siblings, however, the plant does propagate true from leaves. It is quite floriferous at maturity and has been used once successfully in a hybrid with P. forrestii, which has produced 100% seedlings that are just as small or smaller than P. 'Keystone's Bantam'. I am awaiting the first flowering of these seedlings this winter. This is, I believe, the first and only hybrid Petrocosmea to date with white flowers.

So, now that I am blessed with an assortment of white flowered Pets all flowering at the same time, you KNOW that I have to attempt some hybrids among them. P. kerrii might introduce more flowers into hybrids, since it's flowers are often borne in clusters of several flowers each. P. kerrii also has the potential to extend the yellow to the upper petals of the flowers, so in combination with another species with the yellow in the base of the flower, one might acheive flowers with yellow on all petals. P. rosettifolia #3 has a lovely yellow veining down the center of the dark leaves, so more attractive foliage might be possible with it as a parent. So, the potential is certainly there for some exciting new hybrids! Now, off I got to the plant room...........

Barney, The Cat

I've had a few inquiries and requests for a photo of Barney, The Cat. Here he is! My profile description mentions that I am the personal assistant to Barney, which is true. Barney took me on as his "P. A." about twelve years ago, when he was leaving the home of my sister upon the impending birth of my nephew, Matt. Barney was not willing to share a home with a newborn infant, so was actively seeking new accomodations at the time. Finding himself in search of a new residence and "P.A", Barney offered me the position after he had conducted a thorough inspection of my residence. He informed me that my employment was on a trial basis and that I would be offered permanent employment only upon having met his strict standards and requirements. I was reluctantly offered the job.

As can be clearly seen by Barney's expression in the photo, he merely tolerates my presence, and often finds me a nuisance. I am occasionally allowed on the sofa and the bed which he uses daily. When I am allowed to sit on the sofa with him or sleep on the bed with him, I am allowed only along the edge, since he requires the middle of the bed for himself.

Barney observes a strict diet, which he demands to be served, often at three a.m. He drinks only the highest quality and purest of water from an immaculately clean dish. My failure to observe his strict and demanding dietary requirements results in a vocal protest that will not cease until his requirements are met. This vocal display is accompanied by a forceful thrashing of this tail.

Barney, too, is a plant enthusiast, and often enjoys strolling about the plant room and sunroom as I tend the plants. He also enjoys horticultural journals, and will eagerly position himself squarely in the middle of whatever page I am attempting to read in the journal at the time.

Posted by Tim, Personal Assistant to H.R.H. Barney, The Cat.

Petrocosmea cavaleriei - A New Kid in Town

The flower of P. cavaleriei. Very similar in appearance to P. sericea and P. sp. 'HT-2'.




By now, those who have been reading my blog have probably realized how much I love to announce a new addition to my collection of Petrocosmea, and when the new addition is a species, I am on Cloud 9. Recently, I've been enjoying and studying the blooms on P. cavaleriei, which my friend Mike Wenzel of the Atlanta Botanic Garden was kind enough to share with me last year. The label on the leaves I received show it having been collected in 2005, but gives no further information.

This photo shows one of my plants, growing in a four ounce condiment cup, with a diameter of about four inches. The plant is very similar in appearance both in leaf and flower, to P. sericea and P. sp. 'HT-2'. The plant, in all parts, though, is smaller than either of these species, and the leaves have a slightly different shape. Flowers are very similar in appearance to these two species also, with the exception of a much hairier calyx.




The Flora of China description, appears to match my plant pretty closely. FOC lists P. cavaleriei as having been described by H. Leveille in 1911 from material collected in Guizhou, China.

It is always exciting anytime a new species comes into cultivation. I have already distributed a few leaves and plants to friends, in the hope that this beautiful new addition to our Petrocosmea collections will become more widely cultivated and appreaciated. I feel we all have a responsibility to try our best to preserve plant species whenever we can. Often Petrocosmea are found in very limited numbers in a few or perhaps even one lone site on a hilltop or valley that is vulnerable to development or other loss of habitat. As was done with me in this case, the passing along of leavews or cuttings from friend to friend is how many of these rare beauties are distributed. I have acquired perhaps 85% of my Petrocosmea collection via this method. So, share your Petrocosmeas with a friend, you might just be helping to save a precious species from extinction.

A New Seedling Flowers!

P. forrestii's flower is nothing special as far as striking features, but it makes up for the lack of drama by the shear numbers of flowers produced! It was easily the most prolific parent in my hybridizing efforts last year. It rarely failed to produce seed when pollinated by another species.

The flowers of P. duclouxii are among the largest of the Petrcosmea species. The shape is unique as is the deep purple blotch at the base of the throat...something no other species has. (This species is almost certainly NOT the true P. duclouxii..... I feel it matches the description of P. grandiflora more closely.)

The first flower from a cross of P. forrestii and P. duclouxii. A much reduced version of P. duclouxii on spectacularly soft foliage!

Having made 14 new Petrocosmea crosses last year, I am excited to see the cooler months of autumn approaching, for that means the peak season of bloom for my Petrocosmea collection is here! And this year, with the bloom season comes the special bonus of seeing many of those seedlings begin to flower for the first time. This week, I am excitedly watching buds develop on a batch of seedlings resulting from a cross between P. forrestii and P. duclouxii. The first to open is pictured above.

The seedlings resulting from the pairing of the floriferous and compact little species P. forrestii and the large, and equally floriferous P. duclouxii have been my favorites, hands down, in the foliage category. I love the foliage on these little guys! The leaves on these seedlings look like large P. forrestii leaves, but are incredibly furry....the hairs on the leaves are dense, long, and very soft. I have always believed the plants should be experienced with all of the senses, including the sense of touch. One of the endearing charms of many Petrocosmeas is the way the foliage feels when it is touched. These seedlings have among the softest, if not the softest foliage of any in my collection. P. duclouxii has long, soft hairs on the dorsal of the leaves, so I was happy to see that they inherited this feature.

Now as for the flowers, I honestly was not expecting anything spectacular here, since I fing the flowers of both parent species to be nothing special. I made the cross with a goal of a heavily flowered, very symmetrical plant, that did not sucker and was easy to grow. I can't say that I have acheived any of those qualities with just a lone flower on one of twenty seedlings, but there are lots of buds coming, so I am still hopeful of floriferous plants. The flower, as you can see above, is a smaller version of the flower on P. duclouxii. I see no sign of P. forrestii in the flower, other than the flowers' reduced size and less prominent purple blotch at the throat (which P. duclouxii is noted for.).

One last note to make....... As I am seeing more and more flowers opening on Petrocosmea hybrid seedlings, I am noting a curious, and disturbing trend.... Many of the flowers have malformed, or missing anthers. Some, as with the seedling above, also have missing or deformed pistils also. If this continues, it may result in Petrocosmea hybrids that cannot be used for further hybridizing. I'm continuing to watch this. This is also noted in some Sinningias...especially the doubles; in Kohleria hybrids, and in some Chirita hybrids.

The journey continues!!!!

Propagation of Pets - Producing Seeds

Seedpods forming on Petrocosmea forresttii at about 6 weeks after pollination.




Propagation of Petrocosmeas from seeds is unfortunately a rare occurence for most of us. For years, the only option many of us had to grow Pets from seeds was from the small quantities of seed that the late Gesneriad Society Seedfund Chairperson, Maryjane Evans produced. Maryjane was able to produce seeds from gesneriad species when most other people failed. She managed to produce seeds from a few species in the late 1990's and those quickly disappeared from the seedfund list. But, recently I've had some success. I thought I would share what has worked for me, in the hope that others might be able to produce Petrocosmea seeds.

For me, the two key factors that have proven necessary through three flowering seasons now are 1) high humidity, and 2) low temperatures for both seed production and seed sowing. In my conditions, I have been unable to produce any seeds in the absence of either of these factors. When both are present, I get seeds 33% of the time. While not great percentages, it is sufficient to get more seeds than I can grow.

So here's how I do it and what I've learned. First, as the plants start to show buds forming underneath the leaves, I place the entire plant inside a plastic nursery tray that is lined with a section of acrylic blanket cut to fit the tray. This blanket is kept barely moist until I harvest the seed pods. I place a plastic humidity dome over the tray so that the plant is enclosed in a "terrarium" environment. The tray is placed on the light shelves where the Pets normally grow and the plant's care remains the same as always. As the flowers open, I wait until they are open about four or five days. At that time, I note that the stigma has enlarges a bit and if viewed under a magnifying glass, it appears "sticky". At this point it is receptive to fertilization. I remove the pollen from the "father flower" and place as much of the pollen as I can onto the stigma. I label the flower with a small tag containing a number, which I note in my hybrid log with the cross and the date. If fertilization occurs, the stigma will "reorient" itself and will point upwards at approximately a 45 degree angle. The ovary will begin to enlarge. I sometimes remove other flowers and buds on this plant to allow more energy to be focused into the seedpod's formation.

Petrocosmea seeds. This photo was taken by my friend Dale Martens. She photographed a packet of seeds that I had shared with her.




Once the seedpods begin to enlarge, I start to count the days. For me, Petrocosmea seedpods have ripened between 57 and 80 days, depending upon the species used as the pod parent. I harvest the seeds, label them and place most of them into the freezer, inside a double layer of ziplock bags to ensure that no moisture gets to them. In this way, I've had good germination on seeds stored for one year. I only plant a small quantity of the seeds for both insurance in case the first planting does not germinate, and because I do not have the space to grow hundreds of seedlings from each cross. I have now accumulated quite a "bank" of Pet hybrid seeds in my freezer!

Petrocosmea seedlings two weeks after germination. I plant on either straight fine vermiculite or peat pellets that I moisten and sterilize in my microwave for three minutes on high.


I've now sown more than 50 batches of Petrocosmea seeds. I've had some total failures and some thrilling successes. I've learned a couple of critical points. First, the seeds must be sown on sterile medium. I microwave whatever medium I use in the microwave on the high setting for three minutes. I allow it to cool and sow the seeds. I sow the seeds in an enclosed environment, such as a ziplock bag or covered plastic bowl as shown above. The seeds must not dry out. Perhaps the most critical factor, though, seems to be cool temperatures for seedling germination. This has been proven now by myself and four other growers. Petrocosmea seed germination seems to be greatly enhanced by keeping them quite cool...for me around 40 degrees F seems to work best. Warm temperatures in the 60 degree or higher range has resulted in total failure to germinate for me in three seperate experiments and has had the same results for four other growers now. I have no idea why this is a factor for both seed production and germination. Perhaps in nature, the seeds are produced in the winter and early spring months so that the resulting seedlings will have a longer time to produce good root systems before the following winter hits them??? I don't know, but I do know that for me, cool temps are crucial in my environment.

The happy result of persistence in attempts to produce seeds on Petrocosmeas. These are the seedling community pots from three of my current crosses.....where am I going to find the room to grow all of these seedlings???? (Note the tray in front shows the seedlings from a cross I made with the intent of producing miniature Pets....these seedlings are the same age as the seedlings in the other two pots!)

A nursery tray underneath the lights in my basement. These are seedlings from the same cross of P. 'Asa Blue' x begoniifolia. Note the variation in the foliage texture, color and shape.


Once the Petrocosmea seeds germinate, I move them to slightly warmer temperatures to increase the rate of growth. After about a month of age, I begin to fertilize the seedlings as I do my mature Pets. Seedlings usually flower for me in about 8-9 months from seed sowing.

I am often asked if Pets are known to be self-fertile and do the self-pollinate. I have never had a Pet self-pollinate. If I get a seedpod, it is always the result of my crossing activities. So, if the ovary begins to enlarge, I usually always have a successful pollination. Since my success rate is only about 33%, I try to pollinate several flowers. That usually gives me one or two seedpods from each cross. Some pods produce one or two seeds, some hundreds. I've only had an empty seedpod once, on a cross that I attempted to make on a plant that was not in a terrarium. It was the only plant to ever form pods outside of an enclosed environment, but when I opened it, it was empty.

Lastly, I have found that some species seem to be happier to become parents than others. For me, P. forrestii has been a prolific seedpod parent, but has failed as a pollen parent. P. rosettifolia #3 is the same. P. duclouxi, P.barbata 'Keystone' and P. nervosa are also great seedpod parents. P. sericea is a fair parent as either the pollen or seedpod parent. P. minor does not want to cross with any of the other Pets. It has been reluctanct, having only been a pollen parent in two crosses.

So, do try to make some Petrocosmea crosses. I tried every year for ten years before I stumbled upon my current methods. It was just an accident that it worked, but I am most grateful that it did work!!!