Winter aconites in the Rautal valley near Jena

The Rautal – yellow wonderland
The Rautal valley near Jena is known far beyond the borders of Thuringia for its unique mass occurrence of the winter aconite in Central Europe. The yellow carpet of blossoms spreads over almost five hectares and grows larger every year. As soon as the first strong rays of sunshine warm the ground and the days become longer again, the small flowers germinate and cover the otherwise still bare forest floor with their intense shade of yellow. The winter aconite was probably brought to the Rautal as a root bulb together with vines from Southern Europe. It was first mentioned there in 1803.

Accompanying heralds of spring
The hardwood forest, which is home to the mass occurrence of the winter aconite, has been a protected landscape since 1965 and covers an area of 4.3 hectares. In addition to the winter aconites, more than 120 different vascular plants occur in this area, signifying a high species richness for a forest. Among the estimated 1.6 million winter aconites, there are also individual occurrences of liverworts, lungworts or mullein in spring.

Explore the trail of winter aconites
To see the “yellow wonder”, many people make their way to the Rautal valley on sunny spring weekends. For this reason, a hiking trail leading to the winter aconite has been established. It leads through mainly beech forest, past outcrops of rock and, with only a slight incline, leads to the best views of the sea of yellow. However, good footwear is recommended as the path can often be muddy. The trail starts at the road between Jena and the village of Closewitz and can be extended as far as desired through the adjacent “Windknollen” nature reserve.

Documenting plant diversity with Flora Incognita
Did you know? The flowering of the winter aconite is a good indicator for monitoring the phenological seasons throughout Germany. If you have shared your location with Flora Incognita and identify a winter aconite (or other early bloomers), you are making an important contribution to the preservation of plant diversity!

This article was displayed as a story in the Flora Incognita app in winter 2022/23. In the app you can always find exciting information about plants, ecology, species knowledge, as well as tips and tricks for plant identification. Check it out!


The future of key-based plant identification – a user study

Our publication “Towards more effective identification keys – a study of people identifying plant species characters” shares insights into this by systematically examining how well people with different backgrounds in botany perceive, understand and relate morphological plant characteristics. In the end, our assessment suggests a set of design principles for intuitive and user-friendly identification keys.

Read it here: Towards more effective identification keys – a study of people identifying plant species characters


The correct and quick identification of plant species plays an important role in the protection of biodiversity, because people can only protect what they know. Automated species identification via apps like Flora Incognita can help closing the knowledge gap, but still the most common way of identifying plant species is working with character keys in printed books. For laypersons, these keys are often difficult to understand because of the widespread use of technical terms and the lack of easily understandable illustrations.

But biodiversity monitoring often involves or even relies on citizen scientists. In many cases, detailed information on species, phenological characteristics or other markers are required to fulfill the given tasks. To be able to keep and grow the number of citizen scientists contributing to monitoring projects, new approaches to support beginners would be helpful – especially in building species identification skills based on plant characteristics quickly and reliably.

Why is the correct perception of plant characters important?

In this example, you can see pictures of the European buckthorn (Rhamnus cathartica) and the common dogwood (Cornus sanguinea). On first sight, both species look very similar, so the exact perception and description of the leaves’ edges is a determining factor of species identification:

A leaf of Cornus sanguinea, the common dogwood

Cornus sanguinea, the common dogwood

A leaf of Rhamnus cathartica, the European buckthorn

Rhamnus cathartica, the European buckthorn

With its grey-brown bark and often thorny branches, Rhamnus cathartica has elliptic to oval leaves with serrated margins.Cornus sanguinea on the other hand has dark greenish-brown branches with elliptic to oval leaves that have an entire margin.
The determining factor in this case is one adjective that needs to be known, understood and perceived to identify the plant in question.

The study

We conducted an online survey with 484 participants. After assessing the participant’s prior plant and species knowledge, they were given the task to identify morphological plant characters from a number of plant images, supported by pictograms, as shown below.  In total, 25 different plant characters were shown on 6 images from different perspectives.


On average, the participants identified 79% of the characters correctly, even those without extensive species knowledge. Those who declared themselves as intermediate or expert in terms of plant expertise needed less images of the respective plant to give a clear answer, and felt overall more sure about their answer. On average, flower-related characters were identified significantly more often and faster than leaf-related characters. Also, flower-related characters needed less images to find a definite answer.


It seems that with carefully derived plant characters, illustrated by a combination of icons and explanatory text, even complex structures can be understood and correctly addressed even from laypersons. With this, we show that future design of traditional identification keys should not only focus on botanical terms, but also on the users and their current skill set. Improving the species knowledge and learning plant identification methods via apps or printed guidelines can be supported by intuitive icons, descriptions and questions that guide the user through the identification process.


Wäldchen, J., Wittich, H. C., Rzanny, M., Fritz, A., & Mäder, P. (2022). Towards more effective identification keys: A study of people identifying plant species characters. People and Nature.

What is the earliest flower to bloom?

The phenological early spring officially begins with the flowering of hazel and snowdrops. Exactly when the first species begin to flower varies greatly over the years, and it also depends on the location. High up in the mountains it is far colder than in the lowlands. There have been observations as early as December, but in some places as late as mid-February. In any case, the use of Flora Incognita is recommended right from the start of flowering: with every plant identification you contribute to the monitoring of biodiversity! (But only if you have shared your location) – So it is worthwhile to continue photographing early bloomers every year, even if you already know the species. Read more

How do plants survive the winter?

How do plants survive the winter?

Plant cells consist largely of water – if this freezes, it expands. This would damage the cells and, in the worst case, kill the plant. So how do plants protect themselves from freezing to death?

Botanical winter dormancy
The falling leaves of the pedunculate oak, the late-ripening apple and the falling needles of the European larch mark the beginning of the phenological winter. There are warmer days in the Central European climate even in winter, but the plants native here still remain in winter dormancy. The reason for this is the breakdown of certain phytohormones (e.g. abscisic acid), which regulate when seeds and buds (re)sprout after the cold period.


Hibernation as seeds
Annual herbaceous plants die in autumn and only ensure their survival through seeds. These consist of a seed coat, a nutritive tissue and the embryo. Humans use plant seeds as a valuable part of their diet – beans, peas and lentils are rich in protein; wheat and oats provide starch. Some seeds, on the other hand, are high in fat, such as oilseed rape, flax or pumpkin. Their hard shell and low water content protect them from freezing. The duration of dormancy varies greatly among individual plant species, as do the factors that lead to its breakdown. Possible influencing factors are: Humidity, temperature, light conditions and the nutrient content of the soil.


Above-ground withering
Perennials are herbaceous, perennial plants that can survive many winters. Their survival strategy is to store energy-rich nutrients (mostly starch) in roots, bulbs, tubers or the rhizome. New buds and shoots develop from the so-called meristem – a tissue consisting of undifferentiated cells that continuously divide and thus release new cells into the plant body. In winter, these tissue parts often rest as „sleeping eyes“ (botanically: provenance bud) just below the soil surface.


Retreating back into the wood
When deciduous trees show their typical autumn colours, this is a sign that no more new chlorophyll is being produced in the leaves – the constant process of decay is now visibly taking place. Over several days to weeks, the chlorophyll is transferred to the trunk along with other energy-rich particles. The vacuoles therein divide themselves and become enriched with sugar, but also with proteins and other dissolved substances such as potassium, magnesium and phosphorus. Other cell parts – the amyloplasts, become starch reservoirs, which are eventually used up by the time the leaves emerge.


Natural antifreeze
Evergreen plants do not die above ground and keep their leaves. Ice-covered blades of grass don’t break if you step on them – what strategy protects them from freezing? Water freezes at 0° – but not necessarily! Seawater remains liquid because salt, as an osmotically active substance, lowers the freezing point. In plant cells, various sugars, alcohol compounds and also potassium are found as effective antifreeze agents. The more of these molecules are dissolved in the cell water, the stronger the effect of lowering the freezing point.


Cold protection through growth forms
The growth form of the plant also plays a role in frost protection: especially in the high mountains, one encounters dense plant cushions in which the branches stand very closely together. This protects the inner leaves and buds like a blanket from the damaging effects of frost. Plants have found many ways to defy the icy months. But it is also exciting to look further afield! Some plant survival strategies are useful on completely different levels: A study from England for example, found that a dense growth of ivy (Hedera helix) can significantly reduce the number, duration and severity of frost damage to historic walls!

This article was displayed as a story in the Flora Incognita app in winter 2022/23. In the app you can always find exciting information about plants, ecology, species knowledge, as well as tips and tricks for plant identification. Check it out!