This last week was Invasive Species Awareness Week, and New York Restoration Project’s (NYRP) Filomena Riganti, a Project Manager who is an ISA Certified Arborist, did an entire week’s worth of posts to raise awareness about invasive species for the NYRP blog. Filomena was gracious enough to create an extra post just for the UEC blog about the Japanese angelica tree (Aralia elata), which you can read below. To see more of Filomena’s posts on invasive species that we frequently encounter you can visit Filomena’s blog page at https://www.nyrp.org/blog/by-author/37.
Beauty and a Beast by Filomena Riganti
This is National Invasive Species Awareness Week, a subject that deserves our attention. Invasive species are regarded as the second greatest global threat to biodiversity, after habitat loss. Within the United States, there are currently an estimated 4,300 plant, animal, and pathogenic species considered to be invasive—defined by the federal government as an exotic species whose introduction into an ecosystem in which the species is not native causes or is likely to cause environmental or economic harm or harm to human health.
Invasive species, regardless of their point of origin or taxonomy, tend to possess one or more common characteristics: high reproductive rate, rapid growth rate, quick dispersal, and few natural enemies. These traits hasten the establishment and spread of pests, and also makes their management a great challenge.
The best way to manage invasive species is to prevent them from becoming established in the first place, but this is unfortunately easier said than done. Increased international trade and changing land use patterns contribute to the migration of species from their native habitats to other regions. Additionally, many invasive species enter new habitats through intentional introduction, as released pets or as garden specimens, for example, and educating the public about the ecological risk posed by certain species can take time.
Take for example, the emerging threat caused by the spread of Japanese angelica tree (Aralia elata), a small, attractive flowering tree that poses a big threat to urban parks and natural areas. The angelica tree was introduced to the U.S. as an ornamental plant in the 1830’s, but has become an established weed in New York City, Philadelphia, and other urban or disturbed habitats of the Northeast. It spreads aggressively through root sprouts and seed dispersal. Due to its habit of forming thickets and by casting dense shade with its luxuriant canopy, the angelica tree suppresses indigenous understory plants.
Many people often confuse Aralia elata with Aralia spinosa, aka Devil’s walking stick, a plant native to the southeastern United States. The two plants are strikingly similar in appearance – both have the same thorn-covered bark, compound leaves, and white plume-like flowers. The easiest way to distinguish the two plants is to look at the flowers. The flowers of the native Aralia spinosa grow at the end of distinct central stem, while the flowers of the invasive Aralia elata are multi-branching with no central stem.
Control of Japanese angelica tree is difficult, but they can be pulled by hand or dug up to include the whole root system. Long-term monitoring for new invasion will be necessary.