British Yellowhead (Pentanema britannicum) is unlike others in its genus, with fine hairs unlike the “wooley cost” most have. It’s considered an invasive species with no natural enemies. It is known to invest nursery crops, specifically hostas. Once established, it’s difficult to remove from the host plant of which it deprives valuable soil nutrients, making it a threat to plant ecosystems.
I. Appearance and Characteristics
Pentanema britannica, the British yellowhead or meadow fleabane, is a Eurasian species of plant in the daisy family.
Pentanema britannica is native to regions of Europe and Asia and was first observed in North America after introduction to Ontario, Canada in 1928 and observation in Long Island, New York before 1915. Following the introduction of Pentanema britannica in New York, it was then introduced to Michigan in 1990, Minnesota in 2004, and Oregon in 2002.
The current distribution of this species is extensive and includes a multitude of countries spanning several continents. In Europe, this includes Albania, Austria, Belgium, Bulgaria, Czech Republic, Slovakia, Denmark, Finland, France, Germany, Greece, Hungary, Italy, Luxembourg, Netherlands, Norway, Poland, Romania, Russia/USSR (Northern Region, Baltic Region, Central Region, Southwestern Region, Crimea, Southeastern Region), Spain, Sweden, Switzerland, Turkey (European part), and Yugoslavia.
In Asia, this includes China (North and Northeastern), Korea, Iran, Armenia, Kurdistan, Dzhyuungaria-Kashgaria, Mongolia, USSR (Eastern Siberia, Far East, Soviet Central Asia), and several of the Japanese islands (Hokkaido, Honshu, Shikoku, and Kyushu). In North America, this includes Canada (Ontario and Quebec) and the United States (New York, Michigan, Minnesota, and Oregon).
Pentanema britannica is an erect herb up to 75 cm (30 inches) tall, with fine hairs but not the thick woolly coat characterizing some related species. Leaves are lance-shaped, up to 5 cm (2 inches) long. One plant produces a few heads, each on a long flower stalk. Each had contains 50-150 yellow ray flowers and 100-250 yellow disc flowers.
The plant produces the flavonol axillarin.
Observations of Pentanema britannica in various new habitats have led to conclusions that it is capable of thriving in a wide range of temperatures as well as climates, indicated by its presence in Sweden and eastern North America, respectively. A limiting (and thus influential) factor of the successful establishment of P. britannica in new habitats is moisture, with higher moisture levels corresponding to a higher level of invasibility. Furthermore, this species was suspected to have been introduced without any natural enemies, which also has been speculated to contribute to its success as an invasive species
Within its original habitat as well as new ones, P. britannica is known to infest nursery crops, specifically hostas (also known as plantain lilies) in the Netherlands where their roots and rhizomes become intertwined with the hosta root systems. Specifically, root fragments of P. britannica are known to enter under bulb scales.
Once intertwined, this plant is aggressive and hard to remove, and can remain even after the infested hosta roots are washed. The overall impact of this species is that it is harmful, as upon infestation, P. britannica impedes hostas from retrieving valuable nutrients from the soil. It has been identified as posing a threat to the environments that it invades due to having the potential to cause damage to invaded plant ecosystems and loss of native plant life.
Additionally, economic risks have been weighed and taken into consideration, and it has been determined to pose a large one due to the wide range of habitats that it can invade and environmental damage it is capable of causing.
II. How to Grow and Care
Sunlight
British yellowhead flourishes under full sun conditions, which means it thrives with at least six hours of direct sunlight a day. This exposure promotes its health and robust growth, enhancing flower production and foliage vitality. With a tolerance for partial sun, british yellowhead can adapt to moderately lit environments, yet excessive shading may reduce blooming and lead to legginess. In outdoor settings, british yellowhead should be planted in areas where sunlight is ample. Its adaptability indicates some flexibility in light exposure, but for optimal results, a sunny site is preferable.
Watering
British yellowhead thrives in moist environments, akin to its origins near water bodies in temperate regions. It has a moderate drought tolerance but prefers consistent moisture, achieving a balance between hydration and drainage. Watering every week is ideal for maintaining this equilibrium. As an herbaceous perennial, british yellowhead is often cultivated outdoors where it can benefit from natural rainfall patterns, aligning with its need for regular watering during the growing season.
Soil
It prefers consistent moisture without being waterlogged, and thus, well-draining soil is essential to prevent root rot.
Fertilizing
For optimal growth, british yellowhead thrives with regular fertilization using balanced nutrition fertilizers. Apply a granular or liquid formulation with equal NPK ratios every 4-6 weeks during the growing season, adjusting to monthly in winter. Benefits include robust growth and vibrant blooms. Apply 1/4 to 1/2 recommended dose for potted plants to prevent root burn, ensuring soil is moist. Seasonal adjustments are crucial: less frequent in dormant winter months. Whether novice or expert, always wear gloves, and avoid over-fertilization to maintain british yellowhead’s health.
Pruning
Pruning is not typically necessary, but removing spent flowers can encourage additional blooms.
Propagation
British yellowhead is a hardy perennial that thrives in a variety of soil conditions and can be effectively propagated through division. Gardeners should take robust, healthy clumps and carefully separate them into smaller sections, ensuring each new piece has adequate roots and shoots for successful regrowth. These divisions are to be planted directly into prepared soil or grown in pots until established. Regular watering and a little patience will allow the divisions to flourish, enhancing the garden with british yellowhead’s vibrant yellow flowers.
Transplanting
Optimal transplanting of british yellowhead occurs as the chill of winter wanes, typically in the burgeoning warmth from late spring to early summer, ensuring strong root establishment. Choose a sunny spot with moist, well-drained soil for best growth.
III. Uses and Benefits
- Medicinal uses
Pentanema britannica is used in Chinese Herbalism by harvesting and drying the flower. It has been used to treat sputum, as the Chinese found it to be beneficial when phlegm has accumulated in the bronchi. Other symptoms in which it has been found to be a clinical remedy for are nausea, vomiting, hiccups, and flatulence. The severity of the condition determines what part of the plant is used; if the symptoms are mild, the leaves are used, whereas more severe cases require use of the flowers.
A multitude of different chemical constituents have been isolated from Pentanema britannica. Some of the chemical constituents include steroids, terpenoids, phenolics and flavonoids. The majority of these compounds are found in the flowers and have been found to have anticancer, antioxidant, anti-inflammatory, neuroprotective and hepatoprotective properties. Pentanema britannica has pharmacological potential.
IV. How to Control
Some of the first recommendations for controlling P. britannica when it was discovered in Michigan nurseries involved methods of both chemical and mechanical control. It was proposed that, from a mechanical standpoint, deep plowing or cultivation was effective, while Roundup was an effective chemical method of control. When using Roundup, one can be strategic in targeting the “mother plant” of P. britannica, which is known to connect to a network of smaller satellite weeds connected by a network of rhizomes.
Thus, by targeting the mother plant, the satellites can be effectively eliminated while using a minimal amount of the herbicide. A lesser-known form of control is biologic methods, in which known predators (pests) of P. britannica are deployed to consume the weed. One such predator is the moth Hellinsia inulae. There is not much information on the current status of mitigation efforts to control P. britannica.
After detection in its hosta nurseries in 1990, Michigan made efforts to restrict the movement, distribution, and sale of the infested hostas to prevent further spread. It was not until four years later that the Dutch placed P. britannica on their noxious weed list and began taking aggressive measures to treat infested fields and reject them from export as applicable.
