Wallflowers are vibrant, fragrant flowering plants belonging to the genus Erysimum. This diverse group is celebrated for its long blooming season and rich colors. The plant is remarkably robust and has been a staple in gardens for centuries. This article focuses on the biology, cultivation, and safety aspects of this popular garden plant.
Botanical Identity and Classification
Wallflowers belong to the genus Erysimum, a member of the extensive mustard family, Brassicaceae. This genus includes over 180 species found across the Northern Hemisphere, often growing in rocky crevices, which is the source of the common name. While some wallflowers were historically classified under the genus Cheiranthus, modern botanical analysis places most cultivated varieties firmly within Erysimum.
The flowers feature the characteristic four-petaled, cross-like shape typical of the family. These blossoms appear in dense clusters and display a striking color range, including vibrant yellows, oranges, reds, pinks, and purples. Many species are highly valued for their strong, often spicy or honey-like fragrance, particularly noticeable in the spring.
Most garden varieties are categorized as herbaceous perennials or biennials. Perennial types are often short-lived and can become woody over time. Biennials flower in their second year before completing their life cycle. The leaves are typically linear to lance-shaped.
Essential Growing Conditions and Care
Wallflowers thrive best in environmental conditions that mimic their native, often rocky, habitats. The most important requirement is excellent soil drainage, as the plants are highly susceptible to root rot. They prefer soil that is poor to moderately fertile and generally favor a neutral to slightly alkaline pH.
For optimal flowering and fragrance, wallflowers require significant sunlight, ideally six or more hours of direct sun daily. While they can tolerate partial shade, too little light may result in leggy growth and fewer blooms. Established plants exhibit drought tolerance and should not be overwatered, which is a common cause of failure.
Maintenance practices extend the plant’s lifespan and blooming period. Deadheading, the removal of spent flowers, encourages new flower buds rather than setting seed. Perennial varieties benefit from a mid-summer trim to prevent them from becoming woody and promote a compact, vigorous shape. In colder zones, perennial wallflowers may require winter protection, as hardiness varies.
Common Varieties and Safety Considerations
Common Varieties
Many popular wallflower varieties are hybrids prized for their extended bloom time and striking coloration. The English Wallflower (Erysimum cheiri) is frequently grown as a biennial, offering fragrant clusters of yellow, orange, or reddish blooms in the spring. The Siberian Wallflower (Erysimum asperum or E. capitatum) is generally hardier and often features bright yellow or orange flowers.
A widely cultivated perennial hybrid is ‘Bowles’s Mauve,’ known for its long flowering period and rich purple blossoms. Other popular cultivars like ‘Winter Orchid’ and ‘Winter Passion’ have been bred to bloom through mild winters, providing color when other plants are dormant. These varieties are often evergreen in warmer climates and are valued for their continuous display.
Safety Considerations
Wallflowers contain defensive compounds that necessitate caution, particularly around children and pets. As members of the Brassicaceae family, they produce cardiac glycosides. These chemical compounds can affect heart function if ingested. While these compounds serve as a natural defense against herbivores, they make the plant mildly toxic. Therefore, all parts of the wallflower should be considered unsafe for consumption.