Origin
Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox is a species of flowering plants in the Lobeliaceae family. It is native to the eastern part of Africa, specifically the Meru and Kilimanjaro regions of Tanzania and Kenya, respectively. These plants are found growing at an elevation of about 1500 to 3000 meters above sea level. They can occur in various habitats, including moist woodlands, forest edges, rocky areas, and alpine zones.
Common Names
Lobelia deckenii is commonly known as the Meru lobelia, Meru giant lobelia, or Decken's giant lobelia in reference to Baron Carl Claus von der Decken, a German explorer who first recorded the plant in 1861.
Uses
Lobelia deckenii has significant cultural and medicinal importance among the people living near its native range. The plant is often used to treat respiratory ailments such as pneumonia, asthma, and bronchitis. The leaves and stem of the plant possess anti-inflammatory and pain-relieving properties, making them useful in treating bruises, skin infections, and other injuries. The plant's fleshy leaves are also edible and are a good source of moisture for hikers and local people experiencing dehydration.
General Appearance
Lobelia deckenii subsp. meruensis is a large herbaceous plant that can grow up to 10 meters tall in its native environment. Its stem is thick and fleshy, and its leaves are large, simple, and arranged in a rosette at the base and smaller further up the stem. The leaves are elliptical, ending in a pointed tip and have serrated edges. The lobelia flowers are tubular and blue in color, forming a spike inflorescence that can reach a height of 4 meters. The plant has a fast growth rate, and some individuals can live for over 20 years.
Light Requirements
Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox requires full to partial sunlight to grow properly. It should be grown in a location that receives at least six hours of direct sunlight every day.
Temperature Requirements
This plant thrives in moderate to warm temperatures. It cannot survive in temperatures below 10°C or above 28°C. The ideal temperature range for its growth is between 14°C to 25°C.
Soil Requirements
The plant requires well-drained soils that are rich in humus. The soil pH should be slightly acidic to neutral, with a range of 5.5 to 7.0. Sandy loam and loamy soils are preferred over heavy clay soils. The addition of organic matter such as compost, manure, and leaf litter enhances soil fertility.
Cultivation of Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox
Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox commonly grows in Mount Meru, Tanzania, in areas with altitudes of up to 3000m above sea level. The plant thrives in cool, moist areas with plenty of sunlight. Therefore, cultivate it in a well-draining potting mix in a location that receives full sun or partial shade. Lobelia deckenii is not frost resistant, so avoid exposing it to severe cold. Transplant the plant in late winter or early spring.
Watering Needs
Frequently water the plant throughout the growing season to keep the soil moist. However, ensure the soil does not become waterlogged, as it may cause root rot. Irrigate the plant when the top inch of the soil is dry to touch. During winter, reduce the frequency of watering but never allow the soil to dry out completely.
Fertilization
Feed the plant occasionally with a balanced, water-soluble fertilizer throughout the growing season. Mix the fertilizer as instructed by the manufacturer and apply it to the plant once every four weeks. Avoid over-fertilization, as it may encourage excessive foliage growth and hinder the plant's flowering.
Pruning
Prune Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox throughout the growing season to encourage bushy growth and improve flowering. Pinch off the growing tips of the plant using clean, sharp shears, leaving at least two leaves per stem. Deadhead spent flowers regularly to prolong the flowering season.
Propagation of Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox
Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox can be propagated both through seeds and vegetative methods.
Propagation through Seeds
Propagation of Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox through seeds is the most common method. The ideal time to collect the seeds is when the capsules are mature and dry. The collections should be placed in a paper bag to dry out further. Once the seeds are dry, the capsules should be crushed, and the seeds can be separated from the debris. The seeds can be sown immediately into the potting mix. The potting mix should be kept moist, but not wet, and covered with a clear plastic bag to maintain humidity. Germination typically occurs within two to four weeks.
Propagation through Vegetative Methods
Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox can also be propagated through vegetative methods such as stem cuttings, division, and layering. However, propagation through these methods is less common as compared to seed propagation.
Stem cuttings should be taken from healthy plants during the growing season. The cuttings should be around 5-10 cm in length, with at least two or three nodes and should be planted in a potting mix that is kept moist but not wet. The cuttings should be covered with a clear plastic bag to maintain humidity. Rooting typically occurs within four to eight weeks.
Division can be done during transplanting by separating the plant into sections and planting them in individual pots. Layering can also be done by pinning down the stem to the ground and covering it with soil. Within a few weeks, new plants will emerge from the covered stem, and it can be separated and transplanted.
Disease Management
Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox is susceptible to various diseases that can negatively affect the plant's yield and quality. Some of the common diseases that affect this plant include:
- Powdery mildew: This is a fungal disease that appears as white powdery spots on the leaves, stems, and flowers of the plant. It can cause leaf drop and stunted growth. To manage powdery mildew, you can spray the plant with a fungicide like sulfur or neem oil.
- Leaf spot: This is a fungal disease that causes brown or black spots on the leaves of the plant. It can cause defoliation and reduce the plant's yield. To manage leaf spot, you can remove and destroy infected leaves and spray the plant with a fungicide like copper sulfate.
- Root rot: This is a fungal disease that affects the roots of the plant, causing them to rot and turn brown or black. It can cause wilting and death of the plant. To manage root rot, you can improve soil drainage and prevent overwatering. You can also apply a fungicide like chlorothalonil.
It's important to prevent these diseases from occurring by practicing good sanitation, such as removing infected plant material and avoiding overhead watering. Also, avoid planting Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox in poorly drained soil.
Pest Management
Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox is also susceptible to various pests that can cause damage to the plant. Some of the common pests that affect this plant include:
- Aphids: These are small insects that suck the sap from the leaves, stems, and flowers of the plant. They can cause curling and distorted leaves. To manage aphids, you can spray the plant with insecticidal soap or neem oil.
- Spider mites: These are tiny insects that feed on the undersides of leaves, causing yellowing and stippling. They can be managed by regularly spraying the plant with water to wash them away and using insecticidal soap or neem oil.
- Caterpillars: These are the larval stage of butterflies and moths that feed on the leaves of the plant. They can be managed by handpicking them off the plant or using a biological pesticide like Bacillus thuringiensis.
It's important to monitor Lobelia deckenii (Asch.) Hemsl. subsp. meruensis E.B.Knox regularly for pests and manage them before they cause extensive damage. Also, avoid using broad-spectrum pesticides that can harm beneficial insects and pollinators.
