Green Alkanet

Introduction

Green alkanet (Pentaglottis sempervirens) is a perennial herb that belongs to the Boraginaceae family. With its striking blue flowers and broad, hairy leaves, it is both admired for its beauty and scorned for its invasive nature. This plant is often encountered in gardens, hedgerows, and woodlands across the UK, raising questions about its origins, uses, and management.

History in the UK

Green alkanet is native to southwestern Europe, including Spain and France. It is believed to have been introduced to the UK in the 18th century, likely as a garden plant due to its attractive flowers and ability to thrive in various conditions. Over time, it escaped cultivation and became naturalized in the wild. Today, it is widespread across much of the UK, particularly in southern and central regions.

Identification and Characteristics

Green alkanet can be identified by its rough, hairy leaves and vibrant blue, five-petaled flowers that bloom from late spring to early summer. The plant can grow up to 60-90 cm in height. Its deep taproot makes it particularly resilient and difficult to remove once established.

Uses

Historically, green alkanet was valued for its dye-producing properties. The roots contain a red dye, similar to that of the true alkanet (Alkanna tinctoria), which was used in cosmetics and textiles. However, in modern times, its practical uses have diminished, and it is primarily grown for ornamental purposes.

Is Green Alkanet a Weed?

Whether green alkanet is considered a weed depends on the context. In gardens and managed landscapes, it often behaves invasively, spreading rapidly and outcompeting native plants and desired ornamentals. This aggressive growth habit, combined with its resilience, leads many gardeners to classify it as a weed. However, in wild or unmanaged areas, it can contribute to biodiversity by providing nectar for bees and other pollinators.

Eradication and Management

Eradicating green alkanet can be challenging due to its robust taproot and ability to regrow from root fragments. Effective management typically involves a combination of methods:

1. Manual Removal: This is the most straightforward approach but requires persistence. Plants should be dug out, ensuring that the entire taproot is removed to prevent regrowth. This method is most effective when the soil is moist, making it easier to extract the roots.
2. Mulching: Applying a thick layer of mulch can suppress green alkanet by blocking light and limiting its ability to photosynthesize. This method is best used in conjunction with manual removal.
3. Chemical Control: Herbicides can be effective, particularly systemic types that are absorbed and translocated throughout the plant. Glyphosate is commonly used, but care must be taken to avoid harming surrounding vegetation. Herbicide application is best done during the plant’s active growing season for maximum uptake.
4. Regular Monitoring: Given its propensity to regrow, regular monitoring and prompt removal of new seedlings are crucial in preventing re-establishment.

Conclusion

Green alkanet, with its striking appearance and resilient nature, is a plant of contrasts. While its history in the UK as an ornamental plant is well-documented, its invasive tendencies have led to its classification as a weed by many. Understanding its characteristics and implementing effective management strategies are key to controlling its spread and minimizing its impact on native ecosystems and cultivated gardens. Whether admired for its beauty or managed as a nuisance, green alkanet remains a notable component of the UK’s botanical landscape.