Othonna and Senecio are two very similar genera found within the Asteraceae family (Compositae). The Asteraceae group happens to be the largest of all families of flowering plants including numerous garden favorites such as sunflowers, dahlias, chrysanthmums, dandelions and many others. Othonnas are confined to mainly the winter rainfall areas of Southern Africa, with most all species native to South Africa. The geophytes or dwarf caudiciforms are prevalent in the western Cape and Namaqualand. Both succulent and non-succulent species are found within this genus of more than 100 species. Othonnas are quite diverse and range from succulent shrubs, pachycaul trees, and geophytes with underground tubers. The most distinguishing characteristic of this succulent genus is the bright yellow daisy or dandelion like flowers. Othonnas are still somewhat uncommon and only a handful are readily available and only offered from specialty nurseries.

Most Othonnas exhibit smooth often fleshy leaves similar to Crassulas and in some species can resemble a jellybean. All leaves and flowers emerge from branch nodes that look like white woolly tufts. Othonnas tend to be fairly hardy and hassle free however I know that for some they can be extremely difficult. Most of mine receive generous watering during the strict winter growing season and in the summer I never let them go bone dry for too long. During the active growing season I have noticed that a misting of water once or twice a day helps in promoting leaf and flower growth. In the hot summer growing months, place them in a shaded, cooler area of the greenhouse or back them away from getting direct sunlight and/or high temperatures in a window.

As noted earlier, the caudex shape can range significantly between the different species. I have listed some of the more dramatic and interesting species below. The caudex on Othonnas naturally forms both above and below the soil level and in some extreme cases, the caudex thrives wedged in between rooks. All Othonnas should be grown in strong direct sunlight to encourage compact growth during their active growing cycle. A common cacti / succulent soil mix should be ok and additional drainage material would be recommended.

Othonnas tend to thrive in slightly cooler temperatures than most succulents but very similar growing conditions to most African Pelargoniums. Their active winter growing months typically include early fall through late spring or when the daily highs are cooler (Oct. – early May). The warmer months force many Othonnas to go into dormancy and include the summer months (early June – late Sept.). Most Othonnas are summer deciduous, commonly loosing their leaves in late spring with the onset of hot summer temperatures. Most Othonnas are not conducive to Colorado’s cold winters and therefore will not survive outdoors if the temperature reaches less than 40 degrees. However there are some species that can survive the dry winter Colorado months. One such species is Othonna capensis and I have seen this species offered at two of Denver’s local greenhouses.

All of the species found in the Compositae family, Othonnas are distinguished by a flower head that appears to be a single large flower, but is really a cluster of many smaller flowers (florets) protected (and advertised to passing pollinators) by colorful bracts. The flowers of both Othonna and Senecio show resemblance to dandelions and sunflowers. The seeds are held in loose clusters, and scattered by the wind, just as with dandelions. The flower is a bright yellow (occasionally purple) and are long lasting when the temperatures are cooler and water plentiful.

While getting Othonnas to flower and set seed is easy, most of the seeds tend to be no good. To further complicate things, each of the different Othonna species seem to have their own flowering times and germination characteristics (sowing times). On top of all this, the seeds are difficult to germinate once obtained. Most people have had some success by exposing the seeds to temperature fluctuations and sowing seeds in the late fall to winter months where the average daytime high is 50-70 degrees Fahrenheit and the nights get ever colder. By planting seeds in the fall or winter months, maximum growth and development of the water storage tissue is possible before the summer heat. Most seeds will take anywhere from days to weeks and even months before they are triggered into germinating further demonstrating that optimal conditions are a must. One interesting characteristic of Othonna seeds is that viable seeds will form a thin film or mucilaginous coating to help protect the seed and retain moisture.

Propagation from cuttings is also possible and formation of a "typical" caudex is possible. While cuttings do not ensure genetic diversity, it is the easier and the principal method for propagation.

Othonna armiana, O. cacalioides, O. clavifolia, O. euphorbidies, O. lepidocaulis.

For more information on Othonnas, please consult Gordon Rowley's book titled Succulent Compositae. Next month I will discuss caudiciform Pelargoniums. Pelargoniums are not known for a showy caudex but the flowers are truly amazing.

THE AMATEURS DIGEST Caudex Vol. #9, (1999): 11-14.

Rowley, Gordon Succulent Composite. 1994

San Gabriel Valley Cactus and Succulent Society - Succulents of the Month January 2002 - Senecio and Othonna (Tom Glavich December 2001)

If you would like to contact me, you can email me at brad_w_johnson@hotmail.com or visit my website at: http://communities.msn.com/TheCaudiciformPachycaulSucculentSite/_whatsnew.msnw.