Overview
Polystachya johnsonii Kraenzl. is an epiphytic orchid species found in tropical Africa. It is known for its showy pink and white flowers that bloom from October to February. This plant is also commonly called the "Johnson's Polystachya" or the "Pink-spiked Polystachya".
Appearance
Polystachya johnsonii Kraenzl. has long, thin, and narrow leaves that grow up to 20 cm in length, and are borne on pseudobulbs. The plant typically reaches heights of up to 30 cm, and its stem has a cylindrical shape. While the leaves are plain green in color, the flowers are striking. The pink flowers, which are often fragrant, are held on a long inflorescence that is around 30 cm long. Each inflorescence can carry up to 20 flowers, each measuring around 1.5 cm in diameter. The flower's petals are broad and round, while its sepals are slightly narrower, and its fringed lip is the showiest part of the flower.
Habitat and Distribution
Polystachya johnsonii Kraenzl. is native to sub-Saharan Africa, specifically in Angola, the Democratic Republic of the Congo, Ivory Coast, Ghana, Kenya, Liberia, Nigeria, Sierra Leone, Tanzania, Uganda, and Zambia. This plant usually grows as an epiphyte, which means it grows upon other plants and trees, up to 3000 m above sea level.
Uses
Polystachya johnsonii Kraenzl. is primarily used for ornamental purposes, and it is frequently grown in gardens, greenhouses, and other indoor settings. Its showy flowers make it a popular choice among orchid enthusiasts. This orchid is easy to grow and can tolerate a wide range of temperatures and humidity levels.
Light Requirements:
The plant Polystachya johnsonii Kraenzl. requires bright, filtered light to grow properly. It cannot tolerate direct sunlight and needs to be protected from intense rays. It is best to place the plant in a partially shaded area where it can receive some indirect sunlight.
Temperature Requirements:
The plant Polystachya johnsonii Kraenzl. thrives in warm temperatures. It cannot tolerate extreme fluctuations and needs a stable and consistent temperature. The ideal temperature range for the plant is between 18°C to 24°C. It is important to keep the plant away from cold drafts and sudden temperature changes.
Water Requirements:
Polystachya johnsonii Kraenzl. requires regular watering to keep the soil moist. However, it should be noted that the plant is susceptible to root rot, so the soil should never become waterlogged. It is best to water the plant when the top layer of soil has become dry. The frequency of watering may vary depending on the humidity levels and temperature of the environment.
Soil Requirements:
The plant Polystachya johnsonii Kraenzl. requires a well-draining soil mix to grow properly. It is recommended to use a mixture of sphagnum moss, fine bark, and perlite or sand. The soil should be aerated and have good drainage to prevent waterlogging and root rot. The plant can also be grown in a basket or mounted on a piece of wood.
Fertilizer Requirements:
The plant Polystachya johnsonii Kraenzl. requires regular fertilization to replenish the nutrients in the soil. It is best to use a balanced fertilizer with an NPK ratio of 20-20-20. The plant should be fertilized once every 2-3 weeks during the growing season and once a month during the dormant season. Over-fertilization should be avoided as it can damage the plant.
Cultivation
Polystachya johnsonii is an epiphytic orchid that can be grown in a pot or mounted on cork or tree fern. It should be grown in a well-draining and porous orchid mix containing bark, sphagnum moss, and perlite.
It prefers bright, filtered light and does best in warm temperatures between 70-85°F during the day and slightly cooler temperatures at night.
Watering Needs
It is important to keep the soil moist but not waterlogged. Watering should be done early in the day, allowing time for the foliage and roots to dry before nighttime. When watering, it is recommended to use tepid water to prevent shocking the roots and avoid overhead watering to prevent rotting of leaves and flowers.
During the growing season, which is typically in the summer months, the plant will require more frequent watering than in the winter months when growth slows down.
Fertilization
Polystachya johnsonii should be fertilized every two weeks during the growing season using a balanced formula such as 20-20-20 or 30-10-10. It is important not to over-fertilize as this can result in salt build-up and damage to the roots.
Additionally, using a fertilizer high in nitrogen during the winter months can stimulate new growth at the expense of flower development.
Pruning
Pruning is necessary only when the plant becomes too large for its pot or if the roots begin to outgrow the pot. To do this, remove the plant from its pot, cut away any dead or damaged roots, and repot it in a larger container.
Dead or damaged leaves and flowers may also be removed as necessary.
Propagation of Polystachya johnsonii Kraenzl.
Polystachya johnsonii Kraenzl. can be propagated through seed or division of the plant's rhizomes.
Propagation by seed
The seeds of Polystachya johnsonii Kraenzl. are small and rattle around in the capsule, and they should be sown as soon as possible. The seeds can be sown onto a seed-starting mix and covered lightly. Keep the soil moist and warm, and the seeds should germinate in a couple of weeks. Once the seedlings are large enough to handle, they can be transplanted into individual pots.
Propagation by division of rhizomes
Polystachya johnsonii Kraenzl. can also be propagated through division of the plant's rhizomes. Carefully remove the plant from the pot or garden bed. Gently separate the rhizomes, making sure that each division has at least one healthy pseudobulb. Pot the divisions up in individual pots using a well-draining orchid mix, making sure to keep the soil moist but not waterlogged until they become established.
Disease Management for Polystachya johnsonii Kraenzl.
Polystachya johnsonii Kraenzl., like any other plant, is susceptible to diseases that can shorten its lifespan and inhibit its growth. The following are some of the common diseases that might affect this plant:
- Leaf Spot: This fungal disease causes the leaves to have black or brown spots and may cause premature leaf drop. The disease spreads through contaminated soil, water, and tools.
- Stem Rot: This fungal disease affects the roots and stems of the plant, causing discoloration and wilting. It spreads via contaminated soil, water, and tools.
- Viral Diseases: Polystachya johnsonii Kraenzl. is also susceptible to viral infections like mosaic virus that can cause the leaves to become mottled, distorted and stunted. The viral diseases spread through contaminated tools and sap.
To manage these diseases, the following practices should be observed:
- Practicing Good Hygiene: To limit the spread of diseases, the leaves, tools, and pots should be regularly cleaned and disinfected, and the infected plant parts removed and disposed of accordingly.
- Use of Fungicides and Pesticides: Apply appropriate fungicides and pesticides as soon as the diseases are spotted. This should be done as per the instructions on the products and regularly to inhibit re-infestation.
- Use of Disease-resistant Varieties: Choose healthy and resistant varieties of Polystachya johnsonii Kraenzl. to prevent the plant from getting diseased.
Pest Management for Polystachya johnsonii Kraenzl.
Polystachya johnsonii Kraenzl. is vulnerable to insect and mite infestations that can weaken and cause its leaves and stems to look unsightly. Some of the common pests that infest polystachya johnsonii kraenzl include:
- Spider Mites: These tiny pests attack the leaves and cause them to turn yellow and have a stippled appearance. They suck out sap from the leaves and can weaken the plant if not managed appropriately.
- Thrips: These pests are tiny and slender and can infest the buds and flowers of the polystachya johnsonii kraenzl. Their feeding causes deformation, discoloration, and even death of the plant parts.
- Mealybugs: These insects prefer the undersides of the leaves where they feed on sap and cause wilting and leaf drop. They secrete honeydew, which hosts sooty mold that can blacken the plant parts.
To manage these pests, the following practices should be observed:
- Practicing Good Hygiene: The infected plant parts should be removed and disposed of appropriately, and the plant, pots, and tools regularly cleaned and disinfected.
- Use of Pesticides: Appropriate insecticides should be applied to the plant while following instructions provided to prevent further damage to the plant.
- Biological Control: Introduce natural predators like ladybugs or lacewings to prey on the pests. This practice should, however, be used with caution on indoor plants and greenhouses to avoid destabilizing the ecosystems.
- Use of Sticky Traps: These are essential for trapping the flying pests that infest the plant like spidery thrips. The traps should be placed on the leaves and disposed of appropriately once they are full.
