EUROPEAN PINGUICULA : alternative cultivation method.

By Iwein  Coppens, August 2004

iwein.coppens@pandora.be

    In this article I would like to share some growing experience concerning temperate Pinguicula. These Pinguicula species are to be found in relatively high regions of the Alps, the Jura mounts and the balkan region. The method I am going to describe is based on the well known dripping wall system, but is more simplified and does not require special installations.

Growing cycle :

    These temperate species have two different growing periods. In summer they expose a carnivorous rosette of leaves. However in by the end of the growing season, these leaves completely disappear and the plant survives by forming a hibernaculum. These hibernacula are an excellent way of propagation. After two or three growing seasons such a hibernaculum grows into a mature specimen that will flower, provided enough sunlight was present in the previous growing season. Flowering will occur in the beginning of the growing season. Mature plants often expose more than one flower.

An experimental method for cultivation :

    In general carnivorous plant literature will specify these temperate Pinguicula as difficult to keep in long term cultivation. Contrary to what is usually told, I believe that it is quite simple, if some rules are kept in mind. Therefore I would like to share my experience. The species I have successfully tested are: Pinguicula grandiflora, P. grandiflora x fiorii, P balcanica, P.vallisneriifolia en P vulgaris var. bicolor. The only one that didn’t survive was Pinguicula vallisneriifolia.

    As these species grow in mountain regions, soil often consists of rocks, bonded together with organic matters. Keeping this in mind I wanted to try growing these species not in a pot, but on a rock stone. The pores of the stone were filled with a mixture of organic matters, soil, loam and perlite. The advantage of this method to the dripping wall is that one doesn’t need a special purpose built greenhouse.

     So, what kind of rock was used in the experiment? I went to some specialised garden centres looking for suitable rocks. the sheer amount of different rocks was overwhelming.

    The ideal rock would contain several crevices. Every crevice is a possible location to put a plant. It should also have a lot of pores which could draw water by the capillarity effect. The small pores will allow the soil to be moist, even if the rock is not watered from above. for this test I have prepared two different typed of rock. First one is a sandstone based rock, and another has more structure of so called lava rock.

    Before planting the plants in their definitive location, it is recommended to keep the prepared roc in a tray with a couple of cm water. This period can be used to check if the water reaches all desired locations, without need for top watering the rock. During this period the rock can be started up with some mosses to give it a weathered effect. During this testing period is became clear that the sandstone rock is more difficult to keep moist, and that some crevices needed an extra soil bridge to a moist area.

    The planting with Pinguicula was done in early spring. Hibernacula of different species were placed in groups on the rocks (See picture 1 below) .

    On the sandstone rock I planted different species together: At the top, 6 small Pinguicula grandiflora hibernacula were planted at a distance of 4 cm each. During the second growing season on the rock it became clear that this was far too close to each other. I didn’t imagine that the plants would expand so quickly. They even flowered (see picture 2 and picture 3 below).

     At the left sloped edge I placed two specimen of  P. vulgaris var. bicolour. Although P. vulgaris is said to be much more difficult, even these plants showed a first flower in the second season.

    On the other slope following species were planted: P. balcanica, P. vallisneriifolia and the hybrid P. grandiflora rosea x fiorii. These plants didn’t flower yet. As these have expanded their rosette and hibernaculum after the second growing season was definitely bigger than before, I have good hope they will flower in future seasons.

    However not all ended good. My only two plants of P. vallisneriifolia have dried out suddenly and have sadly disappeared.

    The second rock I have planted only one species. Pinguicula balcanica. (see picture 4 below) 

    It soon became obvious that this rock has a much better transfer of moist from rock to the adhered soil. Mosses have already covered a large part of the surface. Due to favourable conditions, the P. balcanica are doing well and the biggest plant even flowered. The  P. balcanica’s  I grow have white flowers with a slight impression of pink.

    Both rocks are in an unheated greenhouse. The greenhouse doesn’t receive full sun until late evening. During the growing season the rocks were placed in a couple of cm water, just enough to keep the surface of the soil moist. During the winter, I have kept the plants outside all the time. The rocks were placed in an insulated box, covered with a glass lid.  During winter the amount of watering was very small. At the end of the winter season the rocks appeared bonedry. I have had no losses due to this dry treatment in winter. All plants that had formed hibernacula before winter, had survived very well.

     If I compare surviving rates of plants cultivated in separate pots to these of plants cultivated on the rocks, my experience is that plants in separate pots are more vulnerable.

Conclusions of the experiment :

    Keeping temperate Pinguicula appears to be less difficult than it is told. Although some rules have to be applied.

    A good balance in the moisture levels is needed during growing season and during winter. Too much water in winter will cause the hibernacula to rot. In summer plants seem to be impossible to recover when soil dried out.

     Also the days of good weather in late winter are dangerous. Plants tend to start growing too early and can be surprised by late frost. For this reason some people keep the hibernacula in the refrigerator until the risk of frost is gone. In this experiment I have kept plants outside during winter, shielded from rain. Rocks and soil were completely dry during winter season. I imagine that these dry conditions prevented the plants from starting too early.

    Also the summer has some difficult days. The hottest days make the plants suffer. We shouldn’t forget that these temperate plants are naturally growing in mountain area’s, where even at full sun, temperatures are not as high as in the average greenhouse.

     It seems that this growing method is quite as good, if not more successful, than keeping plants in separate pots. However during the 5^th ICPS expedition I noticed that the actual natural habitat of temperate Pinguicula is still different.