Urban nature: more survivalists

Some plants are true survivors, they naturally grow ininhospitable situations, for instance rocky crevasses or windswept costal cliffs. Some of these plants have become quite at home in our urban environment, especially due to the heat island effect (which accommodates the less hardy species and annuals) and the sheer amounts of artificial rocks we have created with our walls, buildings and pavements.

Sedum reflexum also known as Prick-madam (left) grows naturally on dry soils and rock, so a garden wall is ideal. This succulent can live off the occasional rain runoff and stores it in its glaucous fleshy leaves. This tiny Bellflower (Campanula rotundifolia) likes the relative dampness this crevasse between the plinth of a building and the edge of the pavement provides. Thrift (Armeria maritima) is often found near the coast, but also thrives along motorways where winter gritting (the application of a mixture of sand and salt) creates an environment that hampers the growth of most plants. This little plant with pink flowers also grows in great abundance on former industrial wasteland, especially with metal pollution.

Other plants grow where few plants manage to hang on to life. Nestling in the gaps between paving slabs these plants either grow very fast making the most of the heat radiating of the concrete, or store food in their roots to resprout after having been destroyed at ground level.

On the left a plant originally from North America that feels right at home in the urban environment: Disc mayweed (Matricaria discoidea). It is an annual exuding a sweet scent when crushed. Finger grass (Digitaria) is also an annual that now grows worldwide, but originated in subtropical Eurasia. It is well at home in pavements where its seeds germinate earlier than in normal soil. The Dandelion (Taraxacum officinale agg.) is known to most people for its seed heads and its yellow composite flowers. The tiny seeds can grow into plants even in between pavement slabs. The taproot grows over time sustaining the growth above. Normally these plants are seen in meadows and lawns.