Overview
Oxytropis nigrescens (Pallas) Fisch. ex DC. ssp. pygmaea (Pallas) Hultén is a perennial shrub belonging to the legume family and is commonly known by several names such as dwarf oxytrope, black locoweed and Locoweed pygmée.
Description
The plant grows up to 2-8 cm in height and forms dense mats or cushions that are up to 30 cm in diameter. Its leaves are mostly basal, curved, and have narrow leaflets. It has a short stem that carries a spike of pea-like flowers that range in color from purple to pink, and occasionally white, in the summer. Its roots are large and robust with a penetrating taproot system.
Origin and Distribution
Oxytropis nigrescens (Pallas) Fisch. ex DC. ssp. pygmaea (Pallas) Hultén is native to the sub-arctic and alpine regions of Eurasia and North America. The plant is found in rocky, gravelly, sandy, and dry soils, primarily in subalpine and alpine habitats. It is widely distributed in Alaska, Canada, Greenland, and Russia.
Uses
Oxytropis nigrescens (Pallas) Fisch. ex DC. ssp. pygmaea (Pallas) Hultén has several medicinal uses. The plant has been found to contain alkaloids that have neurotoxic effects on livestock when consumed in large quantities. In traditional Chinese and Russian medicine, the plant was used to treat joint pain, arthritis, and digestive issues. The plant can also be used as a natural dye for wool and fabrics, producing shades of yellow, green, and brown.
Due to its unique appearance, the plant is also a popular choice for rock gardens and alpine gardens.
Light Requirements
Oxytropis nigrescens ssp. pygmaea grows best in areas with full sun exposure. It requires at least 6 hours of direct sunlight daily for optimal growth and flowering.
Temperature Requirements
This plant can be found growing in arctic and alpine tundra regions, so it can tolerate cold temperatures. It prefers a cool climate with average temperatures ranging between 0°C to 15°C. During the growing season, the optimal daytime temperature range is around 16°C to 20°C, while the nighttime temperature range is around 5°C to 10°C.
Soil Requirements
Oxytropis nigrescens ssp. pygmaea thrives in well-drained soils with adequate moisture retention, such as loam or sandy soils. It is also tolerant of slightly acidic soils with pH levels ranging from 5.5 to 7.5. In its natural habitat, this plant grows in nutrient-poor soils that are low in nitrogen and phosphorus, so it does not require excessive fertilizer application.
Cultivation Methods
Oxytropis nigrescens (Pallas) Fisch. ex DC. ssp. pygmaea (Pallas) Hultén can be grown in USDA hardiness zones 1 to 9. It prefers a location with full sun exposure and well-drained soil. The plant can tolerate high altitudes and cold temperatures, making it a suitable option for mountain gardens.
Watering Needs
Oxytropis nigrescens (Pallas) Fisch. ex DC. ssp. pygmaea (Pallas) Hultén does not require frequent watering, especially if planted in well-drained soil. During the growing season, it is best to allow the soil to dry out between watering. Overwatering can lead to root rot. However, the plant should not be left completely dry for an extended period, as it can stress the plant.
Fertilization
Oxytropis nigrescens (Pallas) Fisch. ex DC. ssp. pygmaea (Pallas) Hultén does not require frequent fertilization. A yearly application of a balanced fertilizer, such as 10-10-10, in early spring can provide necessary nutrients for healthy growth. Over-fertilization can lead to excessive foliage growth and reduced flowering.
Pruning
Pruning of Oxytropis nigrescens (Pallas) Fisch. ex DC. ssp. pygmaea (Pallas) Hultén is not necessary, as the plant generally maintains a compact growth habit. However, dead or damaged branches can be removed as needed to encourage new growth and maintain the plant's aesthetic appearance. Any pruning should be done in late fall or early spring.
Propagation of Oxytropis nigrescens (Pallas) Fisch. ex DC. ssp. pygmaea (Pallas) Hultén
Oxytropis nigrescens (Pallas) Fisch. ex DC. ssp. pygmaea (Pallas) Hultén can be propagated through various methods including seed propagation, vegetative propagation and division.
Seed propagation
Seed propagation is the most common and easiest method of propagating this plant. To propagate using seeds, collect seeds from mature plants and sow them in a well-prepared bed. The soil should be free from weeds and well-drained. Cover the seeds with a thin layer of soil and keep the bed moist by watering regularly. Germination usually occurs in about four weeks. Once the seedlings are a few weeks old and have developed a few sets of true leaves, they can be transplanted into individual pots or in the ground at the desired location.
Vegetative propagation
Vegetative propagation involves taking cuttings from mature plants and rooting them. This method is usually used when seeds are not available or difficult to propagate. This can be achieved by taking 6-8 cm long cuttings from the stem of mature plants and planting them in a well-drained soil. It is important that the cuttings are kept moist and in a shaded area to prevent water loss. Rooting usually occurs within a few weeks, after which the plants can be transplanted into individual pots or the ground.
Division
Division is done by splitting a mature plant into several parts, with each part containing roots and shoots. This is best done during spring when new shoots begin to appear. Dig up the mature plant and gently separate it into smaller parts with a sharp knife. Ensure that each part has a healthy root system and shoots before replanting in a well-prepared soil. Keep the new plants moist and in a shaded area for a few days to allow them to adjust to their new environment.
Disease and Pest Management for Oxytropis nigrescens ssp. pygmaea
Oxytropis nigrescens ssp. pygmaea, commonly known as black locoweed, is a beautiful flowering plant that grows in the alpine and subalpine regions of North America. While it is not particularly susceptible to pests and diseases, it is important to take proper care to prevent any potential damage. Here are some of the common diseases and pests that may affect this plant and ways to manage them:
Diseases
Fungal Diseases: One of the most common infectious diseases affecting Oxytropis nigrescens ssp. pygmaea is root rot caused by Phytophthora fungi. Symptoms of root rot are wilting and yellowing of foliage, stunted growth, and death of the plant. To manage this disease, one must avoid overwatering and ensure proper drainage. If the plant is already infected, it is recommended to remove all infected plants and avoid replanting in the same soil.
Bacterial Leaf Spot: Another infectious disease that might affect the plant is bacterial leaf spot. Symptoms include brown or black spots with yellow halos on the leaves, which can spread to the stems and flowers. To prevent and manage this disease, it is essential to maintain proper ventilation and humidity levels. Infected areas should be removed, and the plant should be treated with a copper fungicide spray.
Pests
Spider Mites: Spider mites are a common pest that might cause damage to Oxytropis nigrescens ssp. pygmaea. These tiny bugs feed on the plant's leaves, resulting in yellow speckles, defoliation, and stunted growth. To control spider mites, it is crucial to maintain proper humidity levels and hygiene. Infected leaves should be removed, and the plant can be treated with insecticidal soap or neem oil.
Aphids: Aphids are another common pest that might damage the plant by sucking its sap, leading to distorted leaves and stunted growth. To manage aphids, one can use a strong spray of water to wash them off the plant. Alternatively, one can use insecticidal soap or neem oil to control them. It is essential to maintain proper hygiene by removing dead plants and debris from around the plant to prevent aphids from proliferating.
Proper care and attention can go a long way in preventing diseases and pests from damaging Oxytropis nigrescens ssp. pygmaea. With regular monitoring and attention to hygiene, one can help ensure the plant grows healthy and vibrant.
