Dr Katarzyna Zolkoś, head of the prof. Fryderyk Pautsch Biological Station at the University of Gdańsk passed away unexpectedly. It is a great loss for the community of our university. She worked with great passion and was involved in educational activities for nature conservation. On June 15, 2021, I interviewed her about invasive plants and the summary of the project: Aliens attack. - Young explorers investigate invasive plants. I did not know that it was the last one. She wanted, in the spirit of citizen science, to promote the possibility of introducing new locations of invasive plants spreading in our region to the inhabitants of Pomerania and creating a map of these species together with an educational path dedicated to the Górki Wschodnie. This talk is a tribute and thanks to her big heart and work for our university and environmental protection.

It's summer, we walk a lot, we see different plants and suddenly we meet in a nearby meadow, park, garden - an 'alien'. Who is it?

Let's start from the beginning, that is, from the two periods of colonisation: before the discovery of America, when plants were brought by old comers, and after - when newcomers arrived. Along with the plant species brought in knowingly, they brought in an intruder of which they had no idea - weeds. We must be aware that there are very different seeds in the yield of every crop. It may be invasive plant species that have been imported in this way. Plants sometimes seem so attractive to us that we bring them in as an ornament. It is worth knowing that these 'aliens' attacking us now were prize winners at world plant exhibitions in the past, and then these plants started to move in and colonise the whole of Europe. We can therefore divide alien plant species into two categories. Those that have come with man consciously (we adapt their genotype to local conditions) and those that we bring in unconsciously.

Canada goldenrod, impatiens glandulifera, Black cherry, E. lobata. The names of invasive plants do not sound threatening, but rather friendly. Why are they dangerous to our ecosystem?

Some of the species we have imported are the so-called queens of one night, or in fact, of one year. These are plants whose seeds cannot overwinter. Invasive species, on the other hand, have a very clever way of adapting to local conditions. What is more, they crowd out native species. The main characteristics of alien species are related to intensive dispersal, i.e. mass production of seeds and rapid movement of the plant.

If they are prettier, stronger, cleverer, why do we need to watch out for them?

I will start with the most dangerous ones, namely the Sosnowsky's hogweed and a very similar one, the Mantegazzi hogweed. These are two very closely related species. The hogweed itself, a species of the Heracleum genus in the celery family, occurs naturally in Poland and our ancestors pickled its leaves - it is edible hogweed. We imported Sosnowsky's hogweed because of its fleshy leaves and very large biomass. The inflorescences, which take the form of a canopy, are on very thick stems. In river valleys, the stem of the plant can reach up to five metres in height. It is the largest herbaceous plant that grows in Poland. The danger lies in the hairs on the leaves, which have reservoirs of a scalding substance. Nettle burns, in which the burning substance is formic acid, are not dangerous. In the case of Sosnowsky's hogweed, the mixture of scalding substances can paralyse nerve cells. When stung, there is no pain. But over time, especially when exposed to sunlight, the toxin breaks down in our body into additional, even more dangerous substances that cause tissue necrosis. Such wounds are compared to third-degree burns and can end up in hospital.

Where did we bring the Sosnowsky's hogweed from?

We brought it from the East, from the Caucasus, during the communist era, hoping that with such a biomass it would be ideal for silage for animals. But it spread uncontrollably, largely thanks to the State Agricultural Farms of the time. It also wandered along river valleys, which is where we can find it. But it was the State Agricultural Farms that were the source of its spread. An example is Trąbki Wielkie near Gdańsk, where there is a large population of both species of this alien hogweed.

Can invasive plants also be dangerous to animals, which, accustomed to local plant food and lacking access to it, can reproduce and migrate less well?

Definitely yes. Just look at the already mentioned Canadian goldenrod. Although it has such a nice-sounding name, it is an invasive species. And we have already lost the battle against it. It was imported as a pollen-growing species, but detailed studies have shown it to be pollen with no added value or vitamins. A kind of gut bomb.

So a kind of cake for the bees?

Something like that, if we look at this type of pollen from the perspective of our honey-growing species, which contain many valuable substances. The goldenrod fields, which we must admit look beautiful, are a landscape that has become firmly established in our consciousness. But the honey harvested from them is incomplete and it is worth knowing this.

Not knowing the dangers of invasive plants, can we plant such an 'alien' plant in the garden, for example, because of its beauty?

Of course, this is the case. Various species of Reynoutria are a case in point. While researching the distribution of these plants in small towns, villages and cities in Kashubia, we discovered something we can call the 'Mrs Zosia effect'. It consists of one neighbour recommending a plant to another neighbour as a kind of practical decoration. Knotweed is very fast-growing, tall and can be used as ground cover for garden fences. The distribution of knotweed literally pointed us to groups of friendly neighbours who recommended and planted this plant to each other.

If knotweed is pretty, practical and fast-growing, what does it lack or have in excess? Is the problem that they are crowding out other species?

Not only. They often form single-species aggregations, taking up large spaces. This is a plant that can reach a height of four metres, and its leaves are the size of a dessert plate. It takes huge amounts of water and nutrients to produce such biomass - this threatens our plants directly. However, a two-centimetre rhizome can also grow into a whole plant and is strong enough to burst concrete. If you plant such a plant near a fence with a concrete foundation, it may turn out that in time, through its underground rhizomes, it will completely destroy your fence.

We want our gardens to look nice, can we buy such an 'alien' at the market, not knowing what we are doing to ourselves?

Not only at the market, but also in large garden shops and supermarkets.

Do we not regulate this by law?

The current legislation in force is the Ministerial Decree on invasive plant and animal species. It only states that such species exist. There is no regulation on the responsibility for maintaining biodiversity in our areas. Due to the toxicity of hogweed, municipalities have taken very effective measures themselves. A new law is already in the pipeline which will regulate responsibility for actions against invasive plants.

In addition to legislation, how can we defend ourselves against such species?

To fight the enemy, you have to recognise it. If we look at southern and eastern Poland, we have nothing to fight for. The soils there are older and better formed, and invasive species are keen to use places that make it easier for them to grow and develop. Such species have already settled in natural or ecologically similar systems there. In Pomerania, on the other hand, we are still 'a day ahead'. We have a colder climate, in which the development of plants is delayed, and they are 'scheming' and if they can choose better conditions, they will choose them. Teams of botanists, also from the Biological Station of the University of Gdańsk, have been studying these plants for a long time. Many articles have been written, noting where these plants occur and how they spread. We tried to create a database using the tools that were available at the time, which were spreadsheets. Our students also took part in the research, and theses were written comparing different areas and the extent of the spread of invasive plants. The results have proven to be very valuable. For example, cutting down or mowing down the Sosnowsky's hogweed, especially the so-called canopy, the part where the seeds are located (there can be as many as forty thousand seeds in one), is only seemingly a good solution. Research has shown that Sosnowsky's hogweed is a biennial plant. The first year the plant emerges and the second year it flowers and dies. Only when we cut it down does it go into a permanent state, becoming a perennial plant. To get rid of it, you have to "trick" it. Botanists from the Hungarian National Park have come up with the best solution of bagging the inflorescence and cutting it down only after the seeds have matured when the plant has fulfilled its 'biological function'.

Today, the 'alien' is recognised with much more modern tools. At the University of Gdańsk, the project 'Aliens attack. - Young explorers study invasive plants'. What are its effects?

The project was primarily educational. It was aimed at the youngest audience. The aim was to improve their ability to recognise alien species, not just invasive ones. This is also the title of the 'Aliens attack' website, which is still up and running. It contains all the information about invasive plants, and everyone can help to mark the places where they occur. You need to learn about these plants, register on the website and send a photo with their location and a questionnaire. There are also tips on how to identify invasive plants and photos with descriptions. We verify the completed surveys and place new locations of invasive plants on the map of Pomerania, marking them with different coloured circles. As part of this project, schools entered data from a specific area - this part has already finished. The individual path for entering new locations is still open. As part of the project, an educational path dedicated to a part of the Sobieszewska Island - Górki Wschodnie - was also created. On its route, we watch invasive plants and solve sentences. A field game was also created and is now available online.

You said that in Pomerania we are 'one day ahead' when it comes to the fight with invasive plants. What does this mean?

Invasive species are mainly found in areas that have been transformed by humans. So far, some of them have not appeared in our forests. We must prevent them from entering our natural ecosystem. First, we need to identify where they occur, and when the new law comes into force, we need to develop programmes with municipalities to combat invasive species. But any such intervention must be analysed so as not to inadvertently destroy the ecosystem and many of its vital species.

Can we somehow make friends with "strangers"?

Being an ecoterrorist, i.e. a person orthodox to nature has never been my goal. We have to accept the presence of some invasive plant species, such as goldenrod. The wrinkled rose is also a good example. It was planted to stabilise the dune substrate along the entire Polish coast. And unlike the invasive sharp-leaf or long-leaved violet willow, it can fulfil its useful function in the ecosystem. It is a highly pollen-producing plant, with a high yield, long flowering season, and also has fruit that is a vitamin C boost for many birds. There is therefore no point in eradicating it. The general idea is not to deliberately introduce alien species but to try to replace them with a whole range of native species or also alien species, but ones that do not have invasive characteristics.

So let's walk, let's visit, and let's look for invasive plants while we're at it, and let's chip in, to our knowledge of them.

This is important, especially because we cooperate with other research centres all over Poland. If we work together on the Pomeranian database, it will be possible to add it first to the national database and then to the European one.

Interview by dr Beata Czechowska-Derkacz, Institute of Media, Journalism and Social Communication, University of Gdańsk, PR specialist for promotion of scientific research.