Common Name: Tittmannia
Scientific Name: Tittmannia (syn. *Pachycarpus*)
Native Habitat: Southern Africa (spanning regions like South Africa, Eswatini, Botswana, Namibia, Zimbabwe)

The genus *Tittmannia* was historically used to describe a group of plants within the milkweed family, Apocynaceae. However, taxonomic revisions over time have determined that these species are more appropriately classified under the genus *Pachycarpus*. Named in honour of Johann Tittmann (1784-1831), a German botanist, the original *Tittmannia* genus reflected the early botanical exploration and classification efforts in Southern Africa. The process of collecting, describing, and classifying plants from this biodiverse region began in earnest with European explorers and botanists from the 17th century onwards, intensifying in the 18th and 19th centuries. The plants now known as *Pachycarpus*, and formerly as *Tittmannia*, are predominantly found across the diverse landscapes of Southern Africa, from grasslands and savannas to open woodlands and rocky outcrops. Their discovery was likely part of the broader botanical surveys undertaken to document the unique flora of the Cape and surrounding areas. Early collectors like Carl Thunberg, William Burchell, and later, explorers associated with institutions like Kew Gardens, systematically gathered specimens, which were then sent back to Europe for study and classification by leading botanists of the time, such as Robert Brown, Joseph Dalton Hooker, and others. While many Southern African plants were discovered and named during this period, the specific species initially placed in *Tittmannia* didn’t necessarily gain widespread fame or cultivation early on compared to some of the more showy or economically significant plants. *Pachycarpus* species are often characterized by their tuberous roots, milky sap (typical of the family), and unique flowers and seed pods. They are not typically cultivated as ornamental houseplants or for widespread commercial purposes, although some species hold ethnobotanical significance in traditional Southern African medicine. The transition from *Tittmannia* to *Pachycarpus* highlights the dynamic nature of botanical classification, which evolves as new information, particularly from genetic studies, refines our understanding of plant relationships. Modern botanists and taxonomists have consolidated various historical genera based on morphological and molecular evidence, leading to the current classification. Therefore, the history of ‘Tittmannia’ is more a chapter in the history of Southern African botanical exploration and the evolution of plant taxonomy than a story of popular cultivation. Interest in these plants today is often driven by specialists in milkweeds, succulent enthusiasts interested in caudiciform plants (due to the tuberous roots of some species), or researchers studying their ecology and ethnobotanical uses. The geographical origins are firmly rooted in the diverse ecosystems of Southern Africa. The specific range varies by species within the *Pachycarpus* genus, but they are largely concentrated in countries like South Africa, Eswatini, Botswana, Namibia, and parts of Zimbabwe, adapting to varying climatic and soil conditions within this extensive region. Their presence across such a wide area suggests a long history of adaptation and distribution within the Southern African flora.

*Pachycarpus* species, historically known as *Tittmannia*, exhibit several notable adaptations to their Southern African grassland and savanna habitats, which are often characterized by periods of drought and intense sun. A primary adaptation is the presence of a large, often underground, tuberous rootstock (caudex) in many species. This structure serves as a vital storage organ for water and nutrients, enabling the plant to survive prolonged dry seasons and fires. The caudex can be quite large, often hidden just below the soil surface. Another adaptation is the production of milky sap (latex), a common feature in the Apocynaceae family. This latex contains various compounds, including cardenolides, which can deter herbivores from feeding on the plant tissue. The tough, often hairy or waxy leaves of some species also help reduce water loss through transpiration. The flowers are complex, adapted for pollination by specific insects, and the large seed pods (follicles) release numerous seeds attached to tufts of hair (pappus), allowing for wind dispersal across relatively long distances, aiding in colonization of new areas.

Propagation of *Pachycarpus* (formerly *Tittmannia*) species is typically achieved through seed or sometimes cuttings, though cuttings can be more challenging due to the plant’s growth habit and milky sap. Seed propagation is the most common and reliable method. Fresh seeds collected from mature follicles have the best germination rates. Seeds should be sown in a well-draining potting mix, lightly covered, and kept warm and lightly moist. Germination can be erratic depending on the species and freshness of the seed. Seed-grown plants will develop the characteristic tuberous rootstock. Stem cuttings can be attempted, particularly from non-flowering stems, but they must be allowed to callus (dry and heal) for several days or even weeks before planting to prevent rot. Once callused, cuttings can be inserted into gritty, well-draining soil mix. Keeping the soil slightly moist but not wet and providing warmth can encourage rooting, but success rates vary greatly between species and can be slower than seed propagation. Division of older, multi-stemmed plants is also theoretically possible but less common and carries a higher risk of damage and infection.

Plants in the Apocynaceae family, including *Pachycarpus* (formerly *Tittmannia*), are known to contain cardiac glycosides in their milky sap (latex). Ingesting any part of the plant, particularly the sap or roots, can be toxic to humans and pets (like cats and dogs). Symptoms of ingestion can include oral irritation, burning sensations in the mouth and throat, nausea, vomiting, diarrhea, and abdominal pain. In more severe cases, especially with larger quantities or in sensitive individuals/animals, the cardiac glycosides can affect heart rhythm and function, potentially leading to irregular heartbeat, weakness, collapse, and in rare, extreme circumstances, death. The milky sap itself can also cause contact dermatitis or skin irritation in sensitive individuals. Due to the potential for serious cardiac effects, ingestion should be considered a medical emergency, and veterinary or medical attention should be sought immediately.

• Aphids (attracted to new growth)
• Mealybugs (often hide in leaf axils or on roots)
• Spider mites (more common in dry, hot conditions)

• Root rot (caused by overwatering and poor drainage)
• Fungal leaf spots (less common, usually due to excessive moisture or humidity)

• Leggy growth: Insufficient light
• Yellowing leaves: Often due to overwatering or nutrient deficiency (less likely if soil is good)
• Failure to flower/set seed: Insufficient light, poor nutrition, or lack of appropriate pollinators

*Pachycarpus* species are not widely available in general horticulture and could be considered relatively rare in cultivation outside of specialist collections. Factors contributing to their rarity include:

• Limited Cultivation: They are not typically grown commercially on a large scale as popular ornamental plants.
• Specific Habitat: They are native to specific regions of Southern Africa, and wild collection is generally discouraged or regulated.
• Propagation Challenges: While seed propagation is possible, getting viable seeds or achieving successful germination can sometimes be inconsistent. Vegetative propagation can also be difficult for some species.
• Slow Growth: Some species, especially those developing large caudexes, can be relatively slow-growing, particularly in cooler climates.
• Specialist Interest: Demand is primarily from specialist collectors of milkweeds or caudiciform plants, rather than the general public.

The market value of a *Pachycarpus* specimen (formerly *Tittmannia*) is primarily influenced by its appeal to specialist collectors rather than mass market trends. Factors affecting value include:

• Species: Some species might be more sought after due to particular flower characteristics, caudex shape, or rarity within the genus.
• Size and Maturity: Larger, mature specimens, especially those with a well-developed caudex or unique form, command higher prices.
• Provenance: Plants originating from reputable growers or collections, or those legally and ethically sourced (e.g., propagated from known parent stock), can have higher value.
• Health and Condition: A healthy, well-grown plant free from pests or diseases is more valuable.
• Collector Demand: As with any niche plant group, value can fluctuate based on current trends and the specific demand within the succulent or milkweed collector community.