Origin
Dendrosenecio johnstonii subsp. refractisquamatus is a subspecies of the giant senecios known scientifically as Dendrosenecio johnstonii and is endemic to the Rwenzori Mountains, located along the border of Uganda and the Democratic Republic of Congo.
Common names
The plant Dendrosenecio johnstonii subsp. refractisquamatus is known by many common names, including Johnston's tree groundsels, Rwenzori giant groundsels, and giant lobelias.
Uses
The plant's large leaves can be dried and used as insulation material for bee hives and homes. It also plays an important role in maintaining the biodiversity and ecosystem of the Rwenzori Mountains.
General Appearance
Dendrosenecio johnstonii subsp. refractisquamatus is a large plant that can grow up to 10 meters tall in high altitudes. It has a tree-like appearance with a single trunk and branches that grow outwards near the top. The leaves are large and can measure up to 1 meter long and are deeply lobed. The flowers are arranged in large, terminal corymbs and have yellow petals.
Light Requirements
Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord. is a sun-loving plant that requires a minimum of 6-8 hours of direct sunlight per day. In the wild, it typically grows in open, exposed areas above the treeline, where it receives ample sunlight.
Temperature Requirements
This plant is adapted to cold temperatures and is therefore best suited to growing in cool environments. Its natural range includes high-altitude areas, where temperatures can drop below freezing. A temperature range of 5-15°C is optimal for the growth of Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord.
Soil Requirements
The soil in which Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord. grows must be well-draining, as this plant is prone to root rot in waterlogged conditions. The ideal soil type for this species is sandy or gravelly, with a pH between 5.5 and 7.5.
It is also important to note that this plant is adapted to growing in nutrient-poor soils. Therefore, adding too much fertilizer can actually be detrimental to its growth. Organic matter can be added to improve soil structure, but it should be done sparingly.
Cultivation Methods for Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord.
Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord. is native to high altitude regions of East Africa, specifically the Rwenzori Mountains. It is a herbaceous plant that grows up to 8 feet tall. To cultivate this plant, it is best to mimic its natural habitat by providing cool temperatures and moist soil.
Watering Needs for Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord.
This plant requires regular watering during its growing season, especially in the first few months after planting. However, it is important to avoid overwatering as excessive moisture can cause root rot. Watering should be reduced during the dormant season to prevent waterlogging or dehydration. It is recommended to water deeply and infrequently.
Fertilization for Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord.
This plant does not require regular fertilization, but it can benefit from occasional doses of an all-purpose fertilizer during the growing season. It is important to avoid using excessive amounts of fertilizer as this may lead to weak growth and susceptibility to pests and diseases.
Pruning for Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord.
Pruning is not necessary for this plant as it forms a single stem with a crown of leaves at the top. However, if it grows too tall, it can be cut back in the dormant season to rejuvenate growth and prevent it from toppling over due to its weight. Dead or damaged leaves should also be removed when necessary.
Propagation Methods for Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord.
Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord. is commonly propagated through its seeds and vegetative means.
Seed Propagation
Seeds need to be collected from mature plants during the flowering and fruiting season which usually happens from January to March. The collected seeds must be immediately stored in a cool and dry place to avoid any moisture which can cause the seed’s decay. The seeds must be cleaned before sowing to prevent any fungal infection upon germination. The ideal temperature for propagating the seeds is between 20 to 25°C. Plant the seeds in a well-draining soil mixture, with good aeration, and high organic matter content. The required moisture level for seed germination is around 40-50% which must be maintained in the soil medium.
Vegetative Propagation
Vegetative propagation is a useful technique for Dendrosenecio johnstonii (Oliv.) B.Nord. subsp. refractisquamatus (De Wild.) B.Nord. As the plant can easily propagate via suckers that form from the roots, or via the stem cuttings. A healthy stem from a mature plant can be cut at nodes which will develop adventitious roots and can be later transplanted to the soil. Stem cutting is usually planted directly into the soil or in a well-draining mix of perlite, peat, and sand. Use of rooting hormone can speed up the growth process.
Disease and Pest Management for Dendrosenecio johnstonii subsp. refractisquamatus
Dendrosenecio johnstonii subsp. refractisquamatus is generally a healthy plant, but there are a few diseases and pests that can affect it. In this section, we will discuss the common diseases and pests that can impact the plant and suggest ways to manage them.
Common Diseases
Fungal Leaf Spot: This is a common disease that can affect Dendrosenecio johnstonii subsp. refractisquamatus. It is characterized by small, dark spots on the leaves. To manage this disease, remove infected leaves and dispose of them properly. Also, avoid overhead watering and improve air circulation around the plant.
Crown Rot: Crown rot is a fungal disease that can affect the plant. It is characterized by a rotting of the plant at the crown. To manage this disease, remove and dispose of affected plants. Also, avoid overwatering and improve soil drainage by adding organic matter.
Powdery Mildew: Powdery mildew is a fungal disease that appears as a white powdery coating on the leaves. To manage this disease, remove affected leaves and dispose of them properly. Also, improve air circulation around the plant and avoid overhead watering.
Common Pests
Aphids: Aphids are small insects that can feed on the sap of the plant. They are commonly found on the undersides of leaves and on the shoots of the plant. To manage aphids, try spraying the plant with a strong jet of water to dislodge them. You can also introduce natural predators such as ladybugs, lacewings, or parasitic wasps.
Spider Mites: Spider mites are tiny pests that suck the sap from the leaves of the plant, causing them to turn brown and die. To manage spider mites, regularly inspect the plant for the pests and spray them with a mixture of water and dish soap. You can also introduce natural predators such as ladybugs or lacewings.
Thrips: Thrips are tiny black or brown insects that feed on the plant's tissues, causing the leaves to become distorted and discolored. To manage thrips, regularly inspect the plant for the pests and remove any affected leaves. You can also introduce natural predators such as mites or parasitic wasps.
By following the above management techniques, you can keep Dendrosenecio johnstonii subsp. refractisquamatus healthy and free from diseases and pests.
