Overview
Erysimum asperum (Nutt.) DC. var. angustatum (Rydb.) Boivin, commonly known as tall western wallflower or narrow-leaved wallflower, is a flowering plant species in the Brassicaceae family. It is a long-lived herbaceous perennial that typically grows in dry, rocky soils and open areas in the western United States and western Canada.
Description
Erysimum asperum var. angustatum grows up to 3 feet in height with an upright, sparsely branched, and somewhat woody stem. It has narrow-lanceolate leaves that measure up to 6 inches long and 0.8 inches wide. The plant produces numerous bright yellow, four-petaled flowers that are 0.8-1.4 inches in diameter. Blooming occurs from May to August. The fruits are long, narrow siliques that contain many tiny seeds.
Uses
Erysimum asperum var. angustatum is primarily used as an ornamental plant for its attractive flowers and foliage. It is a popular choice for rock gardens, wildflower meadows, and xeriscaping. Its seeds are dispersed by wind and can self-sow, making it a good choice for naturalized landscapes. In some native cultures, the leaves and flowers of the plant are used for medicinal purposes, such as treating respiratory ailments and soothing sore throats.
Cultivation
Erysimum asperum var. angustatum prefers full sun and well-draining soil. It is adaptable to a variety of soil types, including sandy, loamy, and rocky soils. The plant is drought-tolerant and does not require frequent watering. It is hardy in USDA zones 5-9 and can be propagated by seed or division.
Conclusion
Erysimum asperum var. angustatum is a beautiful and versatile flowering plant native to the western regions of North America. It is valued for its ornamental and medicinal properties, as well as its ability to thrive in harsh growing conditions. Whether used as a garden staple or a naturalized accent, this plant is sure to impress with its vibrant yellow flowers and unique foliage.
Light Requirements
As a native plant to the western United States, Erysimum asperum var. angustatum is adapted to grow under full sun exposure. Therefore, it requires at least six hours of direct sunlight per day. Although the plant can grow in partial shade, its overall growth and flowering may decrease due to the lack of sufficient light.
Temperature Requirements
Erysimum asperum var. angustatum is a cold-hardy plant that can grow in USDA hardiness zones 4 to 8. The ideal temperature range for the plant is from 60°F to 80°F (15.6°C to 26.7°C). However, it can tolerate temperatures as low as -20°F (-28.9°C) during winter dormancy.
Soil Requirements
Erysimum asperum var. angustatum grows best in well-drained soils that are slightly acidic to neutral with a pH range of 6.0 to 7.0. The plant is tolerant of different soil types, including sandy, loamy, or rocky soils. Still, it prefers rich, fertile soils that are high in organic matter. To ensure optimal growth, the soil should be moist but not waterlogged, and the plant benefits from regular fertilization.
Cultivation of Erysimum asperum var. angustatum
Erysimum asperum var. angustatum is a herbaceous perennial plant that thrives in full sun to partial shade. It is best grown in USDA hardiness zones 5 to 9. The plant prefers well-draining soil with a slightly acidic to neutral pH, and it can grow in various types of soil, including sandy, loamy, and clay soils.
Watering Needs for Erysimum asperum var. angustatum
Erysimum asperum var. angustatum requires regular watering during the growing season, especially during hot, dry periods. However, it requires well-draining soil, so it is crucial to avoid waterlogging. It is best to water the plant in the early morning or late afternoon and avoid overhead watering as it can encourage fungal diseases.
Fertilization of Erysimum asperum var. angustatum
Erysimum asperum var. angustatum benefits from periodic fertilization to stimulate growth and blooming. Use a balanced fertilizer with an NPK (nitrogen, phosphorus, and potassium) ratio of 10-10-10 or 5-10-5. Apply the fertilizer in early spring when new growth appears and again in mid-summer. Be careful not to overdo the fertilization, as it can lead to excessive foliage growth at the expense of blooming.
Pruning Erysimum asperum var. angustatum
Erysimum asperum var. angustatum requires minimal pruning. Deadhead the spent flowers to encourage more blooms throughout the growing season. In early spring, prune back the top growth to promote bushier growth and prevent floppiness. If the plant becomes leggy or crowded, it can be cut back to the ground after blooming to encourage fresh growth for the following year.
Propagation of Erysimum asperum var. angustatum
Erysimum asperum var. angustatum is commonly known as the Western Wallflower. This plant can be propagated through several methods, including:
Seed Propagation
Western wallflowers can easily be grown from seeds. Collect seeds from mature plants when the seed pods have turned brown and dry. Sow the seeds in a well-drained soil mix, and keep it moist and in a sunny location. Germination typically takes around 2-3 weeks.
Cuttings Propagation
Propagation through cuttings is less common for Western wallflowers, but it is still an option. Take cuttings of mature plants during the spring or fall when the plant is not in bloom. Dip the cuttings in rooting hormone, and plant them in a well-drained soil mix. Cover and keep the soil moist. If all goes well, the cuttings should root within a few weeks.
Division Propagation
Western wallflowers can be propagated through plant division, but it is not the preferred method. Divide the plant during the spring or fall when the plant is not in bloom. Carefully lift the plant from the ground, and separate it into small sections. Replant the sections in a well-drained soil mix, and water generously.
Disease Management
Erysimum asperum var. angustatum can be prone to various types of diseases, including:
Leaf Spot
Leaf spot is a fungal disease that can cause circular lesions on the leaves of Erysimum asperum var. angustatum. Infected leaves can yellow, wither, and fall off. To manage Leaf Spot, remove and destroy infected parts of the plant. Avoid overhead watering if possible and only water in the morning to give the plant enough time to dry.
Black Rot
Black rot can cause wilting and yellowing of the leaves of Erysimum asperum var. angustatum, as well as blackening of the stem. The fungus behind the disease can survive in soil for years, making it challenging to prevent. However, good air circulation and proper watering practices can help prevent infection. Remove and destroy infected plants and keep the surrounding area clean and free of plant debris.
Club Root
Club root is a soil-borne disease caused by a fungus-like organism that attacks the roots of Erysimum asperum var. angustatum, causing stunted growth and yellowing of the leaves. To avoid Club root, rotate crops regularly and ensure soil is well-draining. Infected plants should be disposed of to minimize the spread of spores.
Pest Management
Erysimum asperum var. angustatum can also suffer from various pests, including:
Aphids
Aphids are small, soft-bodied insects that attack the leaves of Erysimum asperum var. angustatum by sucking the sap from them. This can cause deformities and weakening of the plant. To manage aphids, spray the plant with a strong stream of water or use insecticidal soap or neem oil.
Cabbage Worms
Cabbage worms are the larvae of white butterflies and moths that can feed voraciously on the leaves of Erysimum asperum var. angustatum, leaving behind holes and ragged edges. To avoid cabbage worms, cover plants with lightweight row covers or apply a pesticide containing Bacillus thuringiensis (Bt). Handpicking is also an effective method to get rid of them.
Slugs and Snails
Slugs and snails can be a nuisance to Erysimum asperum var. angustatum, leaving irregular holes in the leaves and stems. To manage these pests, remove debris around the plant to reduce hiding places for them. You can also use traps, copper barriers, or iron phosphate baits to keep them at bay.
