Origin
Phacelia sericea (Graham) Gray var. biennis (A. Nels.) Brand, commonly known as biennial phacelia, is a species of flowering plant that belongs to the family Boraginaceae. It is native to western North America and can be found in different habitats such as meadows, grasslands, prairies, and open woodlands.
Common Names
Phacelia sericea var. biennis is commonly known as biennial phacelia, silky phacelia, and Douglas' phacelia. The name "phacelia" is derived from the Greek word "phakelos," which means "a bundle" referring to the bundle of flowers at the top of the plant.
Uses
Biennial phacelia has both ecological and horticultural uses. It is an important plant for pollinators like bees and butterflies, as it produces an abundance of nectar and pollen. The plant is also used in habitat restoration projects, particularly in disturbed sites, to improve soil quality and prevent soil erosion. In addition, biennial phacelia is a popular ornamental plant in gardens and landscaping due to its showy violet-blue flowers and attractive foliage.
General Appearance
Biennial phacelia is a self-seeding annual or biennial herb that can grow up to 60 cm in height. The plant has a basal rosette of leaves with the stem bearing several branches topped with an inflorescence of violet-blue flowers. The leaves are up to 15 cm long, hairy, and have serrated edges. The flowers are tubular, bell-shaped and up to 1 cm wide. They are arranged in a cluster at the top of the plant and bloom in late spring to early summer.
Light Requirements
The plant Phacelia sericea var. biennis typically thrives in full sunlight. It is recommended to plant them in areas with plenty of natural light to stimulate robust growth. Insufficient natural lighting may cause stunted growth or lackluster blossoms.
Temperature Requirements
The plant Phacelia sericea var. biennis prefers temperatures ranging from 60-75°F (15-24°C). The ideal temperature for the growth of this plant is between 68-77°F (20-25°C) during the day and 50-60°F (10-16°C) at night. It is sensitive to frost and must be sheltered during the winter.
Soil Requirements
The plant Phacelia sericea var. biennis thrives in a well-draining soil with a pH ranging from slightly acidic to neutral (5.5-7.5). The soil should have adequate nutrient content, with moderate levels of nitrogen (N) and low levels of phosphorus (P) and potassium (K). It grows well in loamy soils with good structure, water retention, and air circulation, but can also grow in sandy or clay soils. Additionally, adding organic matter to the soil can significantly improve plant growth.
Cultivation
Phacelia sericea var. biennis is an easy-to-cultivate plant that thrives in well-drained soil, preferably with a pH between 6.0-8.0. The plant enjoys full sun to partial shade exposure, making it a versatile option for different garden conditions. Seeding can be done in either autumn or spring, and it is advised to protect the young seedlings from frost.
Watering Needs
Phacelia sericea var. biennis requires regular watering, especially during its initial growth stages when the soil should be kept moist at all times. Once the plant is mature, it becomes more tolerant of drought conditions, but it still requires occasional watering during prolonged dry spells.
Fertilization
While Phacelia sericea var. biennis doesn't need any extra fertilization if grown in average soil, it will respond favorably to occasional feeding with nitrogen-rich fertilizers. However, excessive nitrogen can cause the plant to produce more foliage than flowers, so it's essential to maintain a balanced fertilizer application.
Pruning
Phacelia sericea var. biennis does not require extensive pruning. Deadheading spent flowers will encourage the plant to flower more prolifically. Cutting back the plant's stems halfway through the growing season can promote more branching and blooms. Pruning should be done with clean and sharp tools to avoid any damage or infection.
Propagation of Phacelia sericea var. biennis
Phacelia sericea var. biennis can be propagated through both seed and vegetative means.
Propagation through seeds
The easiest and most common way to propagate Phacelia sericea var. biennis is through the use of seeds. Seeds can be collected from mature plants that have dried out or purchased from a reputable seed supplier.
Before planting, seeds must be stratified for at least 2-4 weeks to simulate the cold winter conditions they would experience in their natural habitat. This can be achieved by placing the seeds in a sealed plastic bag with some damp sand or vermiculite and keeping them in the refrigerator.
Once stratified, the seeds can be planted directly into the soil or started indoors in trays. Seeds should be covered with a thin layer of soil and kept moist until they germinate, which typically takes 1-2 weeks.
Vegetative Propagation
Phacelia sericea var. biennis can also be propagated vegetatively through stem cuttings. Select healthy stems from mature plants, ideally in the spring or fall when the plant is not in bloom. Cuttings should be taken from the upper part of the stem and should be at least 3 inches long.
Dip the cuttings in a rooting hormone to encourage root growth and plant them in a well-draining soil mixture. Keep the soil moist and provide indirect light until roots have formed, which usually occurs within 2-3 weeks.
Disease Management:
Although Phacelia sericea var. biennis is a relatively disease-resistant plant, it can still be affected by some diseases that may cause issues in crop production. Among the common diseases affecting this plant include:
- Root and stem rots: These diseases are caused by microorganisms such as fungi and bacteria that affect the root and stem parts of the plant causing discoloration, wilt, and eventual death. To prevent these diseases, ensure the planting site is well-drained, avoid overwatering, and incorporate organic matter to improve soil drainage.
- Fungal leaf spot: This disease is caused by fungi that lead to the formation of lesions on leaves and the eventual defoliation of the plant. Proper spacing between plants, crop rotation, and the application of fungicides can be employed to manage this disease.
- Viral diseases: Phacelia var. biennis is susceptible to some viral diseases that are mainly transmitted by pests such as aphids. Improve pest management practices to prevent aphids and other pests that may spread viral infections from infesting your crop.
Pest Management:
Phacelia sericea var. biennis can also be affected by different pests leading to losses in crop yield and quality. Some of the common pests known to infest this plant include:
- Aphids: These are small insects that often feed on the plant sap leading to stunted growth and the transmission of viral diseases. To manage them, use insecticidal soap or neem oil to control the pest population.
- Spider mites: These pests suck sap from the plant, leading to discoloration, and wilting. Proper irrigation and pest control can be used to manage these pests.
- Cutworms: These pests usually feed on young seedlings, cutting them off at the base. The use of insecticides or the placement of physical barriers around the crop can be used to manage these pests.
Proper pest and disease management practices are essential in ensuring high crop yield and quality. Regular scouting of the plants, early detection of pest and disease symptoms, and prompt control measures can minimize losses and increase profitability.
