PENROCK SEEDS AND PLANTS NEWSLETTER: MAY/JUNE 2002.

SOWING OTHONNA AND SECTION HOAREA PELARGONIUM SEEDS IN THE AUTUMN AND EARLY WINTER. The best month for sowing Othonna and Section Hoarea Pelargonium seeds in Johannesburg is May. Young Othonnas and Section Hoarea Pelargoniums usually require 12-14 weeks to develop from the time they germinate until they enter their first dormancy period. May is an ideal time for sowing since days are warm and sunny and temperatures generally range between 2º and 5º Celsius at night. The mild temperatures usually mean there is little or no “damping off” amongst the young plants. Some methods for germinating Othonna and Section Hoarea Pelargonium seeds are discussed below. Othonnas: Othonnas are indigenous to the Cape Provinces particularly the Western and Northern Cape and the south western corner of Namibia. The rainfall occurs in winter in the Western Cape and the Northern Cape. The south western corner of Namibia receives rain in winter and may also get autumn thundershowers which also occur in the extreme western corner of the Northern Cape. Othonna species have adapted to this rainfall pattern either by flowering in the leafless state such as in Othonna armiana and Othonna herrei, when autumn rains are likely or at the height of the rainy period between July and September. This applies to the majority of species. Othonna seeds germinate well when fresh but good germination results occur for at least 2 years after seeds have been harvested. The best germination mixture consists of 3/6 sandy soil, 2/6 fine river sand and 1/6 sieved germination mix. Germination mix is used for germinating seeds in South Africa and the equivalents are likely to be available all over the world. Seeds should be scattered evenly over the surface of the mixture and large deep propagation trays are ideal for sowing. Seeds should be just covered with a very thin layer of the propagation mix. This can be lightly scattered over the seeds until none of them are visible. The trays should be kept moist until the seedlings are well developed and then watering can be reduced as the young plants start to mature. Othonna seedlings should be grown hard in strong sunlight. This allows them to retain their natural compact habit. Germination takes from 24 hours to 2 months. Some Othonna species germinate erratically over a two year period. Amongst these species are Othonna hallii and Othonna wrinkleana. Some Othonna species are difficult to germinate successfully. These are usually species found on very alkaline soils such as O. hallii and O. wrinkleana. Agricultural lime should be added to the sowing mixture to ensure that the germination mixture is sufficiently alkaline. One large heaped teaspoonful of agricultural lime is sufficient for one large propagation tray. Othonnas should be kept dry during their summer dormancy. Care needs to be taken with some succulent species to prevent the stems shriveling completely during dormancy. This is often done by placing plants out of direct sunlight under greenhouse benches where other dormant plants are not watered during a summer dormancy. Pelargoniums in the Section Hoarea. The majority of Pelargoniums in the Section Hoarea are found in the Western Cape, the winter rainfall section of the northern Cape, the south eastern Cape and the autumn and winter rainfall south western corner of Namibia. The majority of these tuberous plants flower and set seed in the spring and summer. This germinates at its best the following autumn and early winter particularly from late April to early June with a germination peak in May. An ideal sowing mixture is that described above for Othonna species. Seeds should be sown in deep seed trays about 1 cm apart with the top of the seed at ground level or just below. Seeds should ideally be sown in rows each row about 1 – 1.5 cms apart. The sowing medium should be kept moist until the seedlings are well developed. At that time watering can be reduced as the leaves of the young plants screen the soil from the sun. The majority of species start to enter dormancy as the days lengthen and the weather starts to warm up in August. As soon as the leaves have withered the plants should be prepared for dormancy by drying the seed trays. The trays, full of dormant tubers, must be kept completely dry until the following April. Some species in the Section Hoarea are prone to shriveling completely during dormancy such as Pelargonium chelidonium. These species need to be stored out of direct sunlight under greenhouse benches where other dormant plants are not watered in summer. They can also be stored in a well-ventilated storeroom ideally with shelving racks. Some Section Hoarea species reach flowering size in their first year but the majority of species flower in their second or even third year from seed. CEROPEGIA CRAIBII: A NEW SPECIES FROM KWAZULU NATAL. Ceropegia craibii was described by Janine Victor in Curtis’s Botanical Magazine Volume 18 Part 4 November 2001:210-213. The plant has a short annual stem which sprouts from a tuber in early summer. 1-4 extremely beautiful flowers are produced with lime green horizontal corolla lobes. The intricate complex floral structure suggests a special pollinator. Only a few tubers have been located on one hill at the type locality and despite thorough searches no further plants have been located. The type locality and surrounding area consists of numerous hills and mountains near the Bivane River east of Vryheid.