Origin
Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. is a species of flowering plant from the family Fabaceae (legume family) that is native to western North America, specifically to California, Nevada, Oregon, and Washington.
Common Names
This plant is commonly known as bicolor lupine, miniature lupine, and narrowleaf lupine.
Uses
Bicolor lupine is an important forage plant for many wild animals, including deer, elk, and mountain goats. It is also cultivated as an ornamental plant due to its striking bicolor flowers that bloom in late spring and early summer. This plant is also valued for its nitrogen-fixing properties, which enrich the soil and promote growth of other plants.
General Appearance
This plant is an herbaceous perennial that typically grows to a height of 30-60 cm (12-24 inches). It has a deep taproot and erect, unbranched stems. The leaves are palmate with 5-7 leaflets that are 2-5 cm (0.8-2 inches) long and 3-8 mm (0.1-0.3 inches) wide. The flowers are arranged in dense, elongated clusters that are 4-10 cm (1.6-4 inches) long and are pink to blue or purple in color. The flowers have a distinctive upper lip that is raised and a lower lip that is reflexed. The fruit is a narrow, elongated pod that is 3-6 cm (1.2-2.4 inches) long and contains several small, black seeds.
Light Requirements
Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. requires full sun to partial shade to grow properly. It is better to provide at least 6 hours of direct sunlight a day for better growth.
Temperature Requirements
The ideal temperature for this plant to grow and develop properly is between 15°C to 20°C. However, it can tolerate a wide range of temperatures from -15°C to 40°C.
Soil Requirements
The plant requires a well-draining soil that is slightly acidic or neutral with a pH range of 6.1 to 7.5. It can grow in different types of soil such as sandy, loamy, or clayey soil. The soil must be fertile and rich in nutrients such as nitrogen, phosphorus, and potassium.
Cultivation Methods
Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. can be grown either from seeds or cuttings. If starting from seeds, it is recommended to scarify them first or soak them in warm water overnight for better germination. Plant the seeds in well-draining soil with a pH of 6.0 to 7.5 and keep them moist until they germinate in 7-14 days. When the seedlings reach a height of about 2 inches, thin them out to prevent crowding. If growing from cuttings, take them during the spring, and root them in a well-draining medium with high humidity.
Watering Needs
Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. prefers slightly moist soil, but avoid overwatering, which can cause root rot. The frequency of watering depends on the climate, soil type, and age of the plant. In general, water the plant deeply once a week during the growing season and reduce watering during winter dormancy. It is recommended to water the plant in the morning or late evening to avoid evaporation and sunscald.
Fertilization
Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. is a nitrogen-fixing plant, meaning it can convert atmospheric nitrogen into a form that is usable by the plant. Therefore, it does not need much fertilization, especially if planted in nutrient-rich soil. However, if the soil is poor, you can apply a balanced fertilizer with an N-P-K ratio of 10-10-10 once or twice a year during the growing season. Be careful not to overfertilize, as this can lead to excessive foliage growth at the expense of flowers.
Pruning
Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. does not require pruning for its growth. However, deadheading spent blooms can encourage the plant to produce more flowers and prevent self-seeding, which can result in overcrowding. Cut the stem just above the first set of leaves after the bloom fades. Additionally, remove any damaged or diseased foliage or stems to keep the plant healthy and prevent the spread of diseases.
Propagation Methods of Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats.
Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. is a beautiful California native plant that can be propagated by several methods:
Seed Propagation
Seeds of Lupinus micranthus can be collected from the plant during the flowering season. The seeds should be cleaned and stored in a cool, dry place until sowing time. It is recommended to scarify the seeds to break their hard coat and allow water to penetrate. Seeds can be sown directly in the ground or in pots. If sown in pots, they should be kept moist until germination. Seedlings should be transplanted after they have developed their second or third set of leaves.
Cuttings Propagation
Lupinus micranthus can be propagated through stem cuttings. Cuttings should be taken from healthy plants in late spring or early summer when the plant is actively growing. The cuttings should be about 4-6 inches long and should be taken from the tips of the stems. Remove the lower leaves, leaving only a few leaves at the top. Dip the cuttings in rooting hormone and plant in a well-draining potting mix. Keep the soil moist and place in a shaded area. After roots have formed, move the plant to a sunny location.
Division Propagation
Lupinus micranthus can also be propagated through division. This method can be used to split a mature plant into smaller sections, each with its own roots and shoots. It is recommended to do this in the spring when the plant is actively growing. Dig up the plant carefully and separate the roots into smaller sections, making sure that each section has several shoots. Replant the new sections in a well-draining potting mix and water thoroughly. Keep the soil moist and place in a shaded area until new growth appears.
Disease Management:
Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. is prone to fungal and bacterial diseases, which can cause significant damage to the plant. One common disease is powdery mildew, identified by white powdery spots on the leaves. The disease can be managed through proper maintenance of the plant. It is advisable to provide adequate air circulation and avoid overcrowding of plants. Fungicides such as sulfur or copper-based products can also be used to treat the disease.
Another disease that affects the plant is root rot, caused by fungi that thrive in waterlogged soil. Symptoms include wilting and yellowing of leaves, stunted growth, and eventual death of the plant. Proper drainage of soil, avoiding overwatering, and removing infected plants can help prevent the spread of the disease.
Leaf spot, caused by the fungus Phyllosticta concave, is another disease that affects Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. Infected plants show small, circular brown spots on the leaves, which may merge, causing leaf drop and defoliation. Fungicides can be used to manage the disease, and infected leaves should be removed to prevent the spread of the fungus.
Pest Management:
Lupinus micranthus Dougl. var. bicolor (Lindl.) S. Wats. is susceptible to infestations by various pests. Aphids, for instance, are common pests that suck sap from the leaves, causing the plant to weaken and become prone to diseases. Insecticidal soaps and horticultural oils can be sprayed onto the plant to suffocate and kill the pests. A strong spray of water also helps to dislodge aphids and prevent re-infestation.
The bean beetle, which feeds on the plant's leaves, flowers, and seeds, can also be a major pest. Handpicking, applying insecticidal soaps, and planting companion crops such as onions, garlic, and chives can help deter the pests. Another pest to look out for is the spider mite, which feeds on plant juices and causes yellowing of the leaves. They can be managed by spraying the plant with insecticidal soaps or neem oil.
Regular monitoring of the plant for any signs of pest infestation or disease can help prevent and manage any potential problems. Ensuring proper cultural practices, such as adequate watering, fertilization, and pruning, also goes a long way in maintaining healthy, pest-free plants.
