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Mesembs

 

MESEMBS  by Mario Cecarini
Mesembryanthemums (Livingstone daisies), once classified in a family of their own (Mesembryanthemaceae), have now been assigned to the wider family of Aizoaceae and are grouped, more or less, into the subfamily of Ruschioideae. They vary greatly in form and dimensions: some are small plants growing up to a few centimetres only, while others may reach a few metres. In the wild they normally grow in winter, which is the wet season, usually forming clumps. Some are able to store water during the dry summer months, entering some kind of dormant state; others exploit the moisture contained in old leaves to form new ones; some others use their tap-roots as storage organs or bury themselves in the soil. Shrub-like species are perennial, while annuals complete their life cycle within the brief wet season and propagate by setting seed.
     Mesembryanthemums are to be found almost anywhere in South Africa with the highest concentration occurring in Karoo, a winter-rainfall region. Proceeding northwards we come across areas characterized by summer rainfall, therefore Mesembs become rarer, disappearing almost completely in the North Province. However, they are also present on the eastern mountain ranges and further north as far as Ethiopia, Somalia and the Arabian Peninsula. Some can also be found in Australia. For further information visit the page dedicated to Aizoaceae.
     The glossy and showy flowers may be solitary or arranged in an inflorescence and are attractive to pollinating insects. Spring is the blooming season for most of the species which lasts, on average, from three to four weeks. Flowers generally open during the midday hours although species like Faucaria, Lithops, Pleiospilos, Stomatium, Hereroa, tend to do so in the late afternoon or early evening.
     The fruits are capsules, mostly dry, usually with multiple valves. Many of them have the ability to open out on wetting and close on drying (hygrochastic), which ensures the dispersal of seeds even at some distance from the plant. Some genera rely on wind to spread their seeds. Nananthus, Delosperma and Aptenia simply drop their seeds on the ground.
     Mesembs seeds are not difficult to germinate if planted in free-draining sandy soil. In some cases the seed coat may contain chemical inhibitors which cause delayed and uneven germination.
     By the time the second pair of leaves is formed, the plant can be considered established and starts growing quickly becoming a real succulent. Some develop tuberous roots, as is the case with Mestoklema tuberosum.
     A few genera like Conophytum and Lithops are able to camouflage amidst the rocks to defend themselves from predators; others grow on steep slopes. Some plants have thorny capsules or inflorescences, others synthesize toxic substances to deter animals from feeding on them.
    Growing Mesembs is an art perfected by learning from experience and the mistakes we make. To get more information about the growing and flowering season for each genus, please refer to the Cultivation Table. Propagation is fundamental to the conservation of the species, especially of those that are the most endangered or the rarest in the wild; it can be done by cutting or seed. The more closely your climate resembles their indigenous climate, the more likely you are to succeed in propagating these plants (unless you can avail yourself of a greenhouse).
    If you intend to raise them from seed it is best to utilize a propagator with a transparent cover. Even though many species can be sown at any time of the year it is always best to respect the plants natural rhythms. Mesembs that grow in winter-rainfall areas should be sown in the autumn or winter when day-length is short, making sure the soil is not too moist. Genera that are native to the Western and Southern Cape, like Glottyphyllum and Faucaria, which usually receive some rainfall both in the summer and winter, can be sown in any season.
Seeds are prone to fungal diseases (Phytium), therefore it is advisable to store them in small boxes or plastic bags with some powder fungicide (such as Ziram, benzimidazolics). Square pots of 8 to 10-centimetre side make ideal containers for sowing; previously disinfected they are to be filled up to one centimetre from the rim with a sterilized mix composed of 2 parts sand, 1 part acidic soil, 1 part garden soil sieved through a 3-mm mesh. Some species like Argyroderma, Gibbaeum, Pleiospilos and Lithops, though, are best grown in a mix containing less organic matter. Further information can be found on the page about sowing. Germination occurs in less than 20 days at a temperature between 16 and 24°C with a 30% shading from direct light. As seeds emerge we have to reduce air moisture. Seedlings growth is influenced by soil temperature and its nutrients. Pricking out, if thought necessary, can be performed no sooner than one year following germination.
    Vegetative propagation can be obtained either by stem or by leaf cuttings as well as by separating stolons or suckers and also by dividing the clumps. However, the method which is most often used is stem cutting. Conophytums root best if cuttings are taken in the autumn or winter, which coincides with their growing season. As for genera with woody stems, take stem portions approximately 10 cm long, cutting them just below an internode. Then plant the cuttings in a close cabinet, poking them into moist sand. You can find more information on the vegetative reproduction page.
    Special care. Growing your plants in a greenhouse may not solve all cultivation problems. The reason for this is that some species are native to subtropical areas, while others are from warm-temperate zones. Some of them need watering during the summer months, others in the wintertime and some others all year round. That is why it is essential that we know the provenance and habitat of the species we intend to grow, even though many Mesembs are tolerant of a wide range of conditions. Therefore it is preferable to choose plants adapted to similar climate conditions thus requiring the same treatments.
    We should not worry about whether the plant growth follows the cycle of seasons of the northern hemisphere or if it is the other way about: what we should pay attention to is the exact moment in which the plant starts growing and adjust our watering and fertilizing schedule accordingly. These plants respond to day-length and temperatures of the hemisphere they are grown in and their life cycle is regulated by these factors. Still, it is very useful to know the characteristics of the region in which they naturally occur and get as much information as we can about the plant cycle of dormancy and vegetation season, in order to recreate favourable conditions to their growth.
     It is not necessary to overwinter Mesembs inside a greenhouse, even those requiring some extra care; a makeshift structure covered with some plastic or a cold frame will provide sufficient protection from rain and frost. Of course you will have to move them out of the structure as soon as the cold season comes to an end.
     Potting mix. Use the same mix recommended for sowing with the addition of some bone meal.
    Location
. Almost every species of Mesembs prefer full sun but since they can get burned quite easily it is best to exposed them gradually to the sunlight at the beginning of the warm season.
    Pollination. Nearly all Mesembs do not self-pollinate, although flowers are bisexual, therefore you can cross-pollinate plants of the same species only if they are clones of different parent plants. In the wild pollination is carried out by insects. Cleitogamous (self-fertile) species are very rare.
Seeds may be collected once capsules are dry. You can choose either of these two methods: the first one is wetting the capsule so that it can open up and naturally release the seeds; the second one consists in placing the capsule between two thin cardboard sheets, crushing them with a blunt object. Seeds need to be stored in a dry place and remain viable for several years, especially if kept in a cool environment such as your fridge (ideal temperatures are  between 3 and 10°C).
     Watering. Mesembs are able to tolerate long dry periods but thrive if watered well occasionally and sprayed with room temperature water during the hottest hours. Leaves that begin to shrivel are a clear symptom of water deficiency. Watering schedule depends on weather conditions, temperature, humidity, soil properties and type of container. Do not water during their rest period.
    Parasites. Many diseases can be prevented by ensuring cleanliness of the places where plants are kept, as well as of gardening tools and containers. If you notice that a plant has been attacked by fungi or mould, you must isolate the specimen at once in order to prevent the disease from spreading. Damping off of seedlings and soft rot are also caused by a type of fungus which can be controlled with a suitable product (like Ziram, Iprodion).
Often check plants for parasites, possibly with the aid of a magnifying lens, like red spider mite, aphids, mealy or scale bugs, caterpillars and slugs.
For more information go to "Diseases" page.

If you wish to know more about all the genera and their species we advise you to read the book "Wygies, gems of the Veld" by E.J.van Jaarsveld and U. de Villiers Pienaar.

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