Is the Canada goldenrod, which is "despised by everyone," a flower or a weed?

Produced by: Science Popularization China

Produced by: Jiang Shan (Wuhan Botanical Garden, Chinese Academy of Sciences)

Producer: Computer Network Information Center, Chinese Academy of Sciences

On November 12, the topic "Wuhan citizens please report this yellow flower if you see it" topped the Weibo hot search list, attracting the attention of many netizens. According to reports, on November 10, eight departments in Wuhan City jointly held a meeting to deploy governance actions, calling on citizens to report if they see this flower and remove it.

So, what kind of flower is this, and what kind of harm will it bring to the local ecology?

Image source: CCTV Finance WeChat Official Account

Grass from the genus Solidago

This plant is called Solidago canadensis L., a perennial herb of the genus Solidago in the Asteraceae family.

There are four species of Solidago in China. Except for Solidago canadensis, the other three are native species, namely Solidago decurrens, Solidago virgaurea and Solidago pacifica.

Although all of them have "Goldenrod" in their names, Canada goldenrod is fundamentally different from the other three species. That is, it is not only an alien species, but also a "domineering" invasive species.

1. It’s an invasive plant

Before we get to know "invasive species", let's first talk about the concept of "alien species".

First of all, the concept of "alien" is not limited to a narrow geographical concept, but refers to the entry of a species into a new area where it has never been distributed in its evolutionary history.

Secondly, this species achieves a certain degree of dominance in the new ecosystem it enters, disrupting the balance of that ecosystem and threatening the survival of the original species.

If a species accidentally enters an ecosystem where it has never been distributed, but dies before it can accomplish its mission due to "acclimatization", or ends up being "alone and helpless" because it has no competitive advantage, then it cannot be considered an invasive species.

Again, this species poses varying degrees of impact on socioeconomics and human health.

From this we can see that although tomatoes, passion fruit, peppers, carrots, etc. are alien species, they either make us taste good or are pleasing to the eye, and their distribution is under the absolute control of humans, so they can never be considered invasive species.

2. It spreads due to human activities

Currently, the vast majority of biological invasions around the world are related to human activities such as trade, transportation and tourism, while the introduction of alien plants as ornamental plants is the main way to cause large-scale invasions of invasive plants.

Canada goldenrod was introduced to Shanghai in 1935 as an ornamental plant because of its brightly colored flowers. It was then introduced from Shanghai to Nanjing, Wuhan, Hefei and other places.

On the open spaces on both sides of the Hefei-Nanjing Hening Expressway, there are Canada thistles distributed along the road. Therefore, the spread of Canada thistles in China is closely related to its introduction and human transportation, trade and exchanges.

"Curse of the Golden Flower"

There are three main reasons why Canada goldenrod is called the "ecological killer" and "the king of flowers".

First, its seeds are huge in number, small in size, light in weight, and have pappus. They can drift with the wind or migrate by sticking to moving objects, making them easy to spread over a large area.

In the warm and suitable southern region, each Goldenrod plant has an average of more than 1,500 flower heads, each of which can produce an average of 10-15 seeds, with a seed germination rate of 43%. According to a rough estimate, a plant of Canada Goldenrod can produce more than 20,000 seeds in a growing season, sprouting nearly 10,000 seedlings.

Second, it has a strong reproductive capacity. In addition to sexual reproduction through seeds, it can also reproduce asexually, but it uses rhizomes, just like the roots of bamboo, which spread everywhere underground and quickly form a forest after two or three years.

The third is to secrete allelopathic substances that inhibit the growth of other organisms. As a plant of the Asteraceae family, Canada solidago can release allelopathic substances that inhibit the growth of other plants.

In short, Canada goldenrod has a very strong growth competitiveness. It occupies space and crowds out the growth of other plants. It not only competes with surrounding plants and cash crops for sunlight and fertilizer, causing a direct reduction in the yield of many cash crops, but also has an inhibitory effect on native plants, posing a serious threat to biodiversity. It can be said that "the whole city is covered with golden armor."

Solidago canadensis (Photo from Solidago canadensis, a Flower or Weed?)

Lend you a pair of "wise eyes"

Autumn is the flowering period of Canada goldenrod, and it is also the best identification period. We should seize the favorable opportunity and carry out prevention work before the seeds mature.

First, we should learn how to identify Canada goldenrod.

The way to distinguish Canada solidago from the other three native species of solidago is that the flowers of Canada solidago only grow on one side of the inflorescence, while the inflorescences of the other three species of solidago grow all around.

Left: Canada goldenrod (Photo source: Wiki Commons)

Right: Goldenrod (Image source: China Plant Image Database)

Left: Solidago serrata Right: Solidago obtuse

(Image source: China Plant Image Database)

Secondly, we should understand the prevention and control methods of Canada goldenrod.

On the one hand, targeted prevention and control measures can be carried out according to the occurrence location and characteristics of Canada goldenrod, such as recultivation and replanting, and manual removal. If possible, its underground rhizomes should be completely dug out to prevent perennial root regeneration; on the other hand, after cutting Canada goldenrod, different chemical agents can be prepared for thorough prevention and control.

This time, "Wuhan citizens please report this yellow flower if you see it" ranked first on Weibo's hot search list, which shows that the public's awareness of biodiversity protection is gradually increasing.

We should always bear in mind that biological invasions not only threaten the stability of ecosystems, but also have serious impacts on local socio-economy, human health and biodiversity.

If we personally want to do something for biodiversity conservation, then we can clean our backpacks before returning from a trip; manage our own aquariums, keep a close eye on our pet red-eared sliders, golden apple snails, giant African snails, and crayfish (Procambarus clarkii) in our kitchens; and report Canada goldenrod when we see it, which is a piece of cake.

References:

1. Don’t mistake the fashionable-sounding “Canada goldenrod” for an invasive species. Guokr.com

2. A brief discussion on the harm and control techniques of Canada goldenrod. Anhui Agricultural Science Bulletin

3. Canada goldenrod green control "four in place" pest control

4. Alien Biological Invasion - A War Without Gunfire. China Agricultural Press