The harsh, brutal urban environment is increasing. In Europe, the Netherlands ranks as one of the countries with the lowest forest cover (10%), with wooden forests being replaced by concrete jungles. Seas of asphalt, bricks and cement dominate as ground cover, while masoned walls provide shade. The sun’s warmth, absorbed by the black asphalt, is retained within city walls through a phenomenon called the urban heat island. Water is scarce, and the soil nutrient-poor. Compared to the forest, little biodiversity can persist in such an unforgiving environment. However, those with keen eyes can find a little act of defiance every spring: the tiny flowers of Draba verna sticking up from in between pavement tiles.
Where no one will grow
Draba verna L., commonly known as Common whitlowgrass or Spring whitlowgrass, is a small but resilient organism that has found its niche in the harsh urban environments across the world. It is an early-flowering annual plant with small, white flowers, often standing just centimeters off the ground. The plants appear in colonies in early spring, with first flowerings in cities starting mid-February. By the end of April, the entire plant will have died off and its seeds dispersed. This diminutive member of the mustard family (Brassicaceae) has adapted remarkably well to the challenges presented by city landscapes, thriving in areas that might otherwise seem inhospitable to other plant species. In its native habitat, Draba verna thrives in disturbed soils such as roadsides, heath meadows, and dune clearings. It is a pioneering species and is often one of the first plants to colonize bare, disturbed ground where nothing else will grow. Its ability to grow in these nutrient-poor and dry soils already made it a hardy species in its natural habitat.
The diminutive plants can grow in tiny patches of soil in between the pavement.
The urban environment as an advantage
In cities, it is often found growing in tiny cracks in sidewalks, along roadsides, next to lamp posts, and other areas with just mere centimeters of disturbed or exposed soil. While water availability in these urban environments can be unpredictable, its ability to germinate and establish quickly allows it to complete its life-cycle before water scarcity can become a limiting factor. Its pioneering nature also allows it to outcompete other slower growing species. The plant’s tolerance for heat and dry conditions enables it to thrive in the warmer microclimates found in cities, particularly in early spring when the ground warms earlier than in rural areas. Together with its early blooming, this gives Draba verna a head start over possible competitors, allowing it to complete its life-cycle long before others start growing. The white flowers cover the pavement and roadsides, taking advantage of the available sunlight before spring vegetation blocks it. As an autogamous plant, Draba verna is capable of pollinating its own flowers. This is an important advantage in concrete jungles where pollinators are often scarce, making it possible to complete its life-cycle even in urban environments far away from their natural habitat and pollinators.
Unjustly, Draba verna remains a neglected plant. The incredibly successful and resilient member of the urban flora is largely ignored, or, when noticed, considered a weed. However, its presence in urban environments can also indicate soil health. Draba verna’s ability to colonize disturbed and bare ground suggests that certain areas may need more intensive greening efforts. In this sense, Draba verna acts as a pioneer species, paving the way for more diverse plant communities in urban spaces. Its presence can also be seen as an important ecological addition to urban green spaces, creating microhabitats for insects between the pavement tiles, thereby supporting biodiversity. The plant’s ability to colonize areas with minimal soil also makes it useful in green roof designs or in creating low-maintenance ground cover in difficult urban spaces.
In short, we should all appreciate what grows in between the pavement cracks more and try to enjoy the little defiant flowers while we can.
A larger, more robust plant from a humus pocket in the concrete.
References
Buch, C., & Jagel, A. (2018). Draba subgen. Erophila – Hungerblümchen (Brassicaceae). Jahrb. Bochumer Bot., 9, 207–211.
Denters, T. (2020). Stadsflora van de Lage Landen. Fontaine Uitgevers.
Duistermaat, H. (2020). Heukels’ Flora van Nederland (24th ed.). Noordhoff.
Eurostat. (2022). Forests, forestry and logging. https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Forests,_forestry_and_logging
Li, D., Stucky, B. J., Deck, J., Baiser, B., & Guralnick, R. P. (2019). The effect of urbanization on plant phenology depends on regional temperature. Nature Ecology & Evolution, 3(12), 1661–1667. https://doi.org/10.1038/s41559-019-1004-1
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