Why we are inspired by imagery of flowers – “weeds” – growing in concrete and asphalt cracks. It’s the way of nature, but it also suggests repairs are needed.

“A Tree Grows in Brooklyn,” the 1943 semi-autobiography by novelist Betty Smith, is a story of resilience against inopportune circumstances. That tree, like many other “weed” saplings that manage to thrive in what appear to be harsh conditions, symbolizes inspiring tenacity for the book’s main character – and its legions of fans.

But in the concrete and asphalt environments of all New York boroughs – as well as on play lots in California, parking lots in Florida, and airplane runways in Illinois – it’s not at all surprising to see a daisy, a shoot of dill, or any number of flowers and grasses that find their way into a small fissure in the pavement. Seeds carried by wind and birds lodge in tiny cracks that have a tiny amount of dirt and which capture a tiny amount of rain.

Of all those seeds, just one needs just a tiny bit of growing media (dirt) to germinate and take root. When the ambitious plant produces its own flower, it’s hard not to notice its yellow or red or blue or white color against the grey concrete or black asphalt.

For as pretty as they are, those flowers can also be a sign that the pavement is in need of asphalt repair. If not, water and roots doing what they do, in a few years it will need wholesale replacement and an asphalt contractor will need to be contacted.

Like Smith’s book, these are things that inspire us. A simple search online, such as on Pinterest, for “flower growing from crack in asphalt,” yields scores of photos of many such plucky plants. Captions for several tell a story: ”Life will find a way,” “Persistence is fertile,” and “To innovate within concrete, start with the cracks.” They might make great inspirational posters.

Looking at it a bit more scientifically, and with far less prose, the business of plants growing in hard surfaces is basically how ancient rocks became dirt. In a process geologists refer to as mechanical weathering (some call it biological weathering), roots of plants that take hold in tiny cracks ultimately break apart those rocks. The bigger the plant, the more power to do this. It may start with tiny mosses and lichens, but eventually those weed trees in Brooklyn can upraise and separate slabs of concrete sidewalks and sections of asphalt pavement.

Other things that break apart rocks (and concrete and asphalt) are water, frozen water in particular, but also seawater. In a process called haloclasty, saltwater gets into tiny fissures of any hard surface, leaving behind salt crystals. The water itself evaporates but the salt stays behind. With the endless cycles of saltwater tides and the cycles of evaporation, the salt crystals accumulate and put pressure on rocks, slowly breaking them apart.

All of which is to say few things are permanent in life – even the largest rock in the world, the 1,100 foot monolith known as Uluru (the former Ayres Rock, in central Australia), is slowly – very slowly – being eroded by weathering, erosion, and those persistent, tenacious if scrubby plants. But quite like sidewalks and parking lots made of concrete and asphalt, it’s the human hikers that are causing the most deterioration.

Since 2019, those hikers have been banned from climbing on Uluru. The plants growing in its cracks, however, as in Brooklyn, New York, are not and cannot be deterred. There are few things more determined than a daisy.