More and more often, cities are experiencing two extremes at once: intense downpours that turn streets into streams, and long rainless periods when plants weaken and the soil cracks. In response, we usually talk about planting trees, because trees are a visible symbol of change. The thing is, without water even the best plantings become a short-lived effect.
That is why the key question today is not only “how many trees,” but: can the city retain water, clean it, and give it back to greenery when it is needed most. This is exactly what the “wet greenery” approach describes – designing greenery and retention as one coherent system.
Why does water “disappear” in a few minutes in the city
In an urban environment, water has a harder time than in a natural landscape. Sealed surfaces – asphalt, paving blocks, concrete – cut it off from the soil. Rain that used to soak in and feed plants now quickly runs into the sewer system. The effect is paradoxical: after an intense rainfall the risk of local flooding increases, and a few days later the soil and greenery suffer because there is nothing for evaporation and transpiration to “work with.”
As a result, trees begin to function like organisms in energy-saving mode: they limit transpiration, close their stomata, grow more slowly, and tolerate heat stress worse. Residents feel this as hotter streets, more stifling nights, and less comfort in public space – even when, “on paper,” the city does not lack greenery.
What is “wet greenery” and why does it work better than plantings alone
“Wet greenery” means a way of thinking in which greenery and retention are one system. It is not only about large reservoirs or expensive hydrotechnical investments, but about ensuring that rain – especially intense rain – does not disappear from the city in a few minutes. If water is to stay, it needs space in the ground and sensibly guided runoff.
In practice, wet greenery means designing greenery so that it takes in water from nearby surfaces (sidewalks, streets, roofs), filters it through soil and substrate layers, stores moisture in the root zone, and then releases water gradually to plants and the atmosphere. Such a system works like a natural sponge: it softens rainfall peaks, reduces the load on the sewer system, and creates a moisture buffer for times of drought.
Soil: the foundation without which retention does not work
The most underestimated element here is soil. Without it, retention becomes decoration rather than a solution. Compacted, degraded soil with a low content of organic matter will not accept water even if there is a nice flower bed nearby. Water will run off the surface, and plants will still require watering.
That is why real improvement starts with the quality of the substrate: its structure, permeability, ability to store moisture, and biological life. If the soil is “dead,” the city can invest in saplings, but it will pay for watering and replacements. If the soil works, plants cope better on their own and maintenance costs drop in the following seasons.
At One More Tree we increasingly emphasize that planting is only the beginning, not the end of change. A tree may be planted correctly, but if it has no access to water and stable soil conditions, the effect can be short-lived. That is why, alongside the plantings themselves, the “invisible” elements are just as important: substrate quality, space for roots, and retention solutions that make sure rain does not disappear from the city in a few minutes. This is exactly where wet greenery stops being a slogan and becomes a practical condition for durability.
From “drain as fast as possible” to “keep it where it fell”
For years the dominant model was: collect water from streets and get it into the sewer system as quickly as possible. With increasingly frequent downpours, this approach has limitations—drainage systems are overloaded, and the city loses a resource that could stabilize the microclimate.
That is why more and more cities are moving toward the logic of “keep water where it fell.” The design of streets, squares, and courtyards is changing. Greenery stops being a thin strip of lawn and becomes an element of infrastructure with a specific task: to cool, irrigate, filter, and stabilize.
What wet greenery looks like in practice
The best results do not come from one “big project,” but from a set of dispersed elements that together capture water: rain gardens and retention basins, bioretention strips (bioswales) along roads and parking lots, de-sealing surfaces and permeable pavements where possible, trees planted in conditions that provide real substrate volume and water inflow, as well as green roofs and “blue-green” solutions that flatten runoff from buildings.
What matters is that well-designed wet greenery is “visible” not only during a downpour. It improves the microclimate every day: it increases local humidity, limits the heating of surfaces, and allows trees to maintain activity during the most difficult weeks of summer.
Why a systemic approach makes the biggest difference
Wet greenery makes the most sense when it is implemented consistently, not as a one-off fix. If in one place you create space for water, but the surrounding area remains fully sealed, the effect will be limited.
The biggest difference is made by a systemic approach: planning greenery where water naturally flows; limiting sealed surfaces; designing substrate that will accept rainfall and keep it in the soil profile; and maintenance that allows plants to take root and enter a stable seasonal rhythm. This approach is also more honest in communication: instead of promising an immediate change after one planting event, it shows a long-term improvement in the city’s resilience.
The role of companies and communities: partnerships that sustain the effect
Retention in public space often requires partnerships. Companies that want to support ecology in a real way can think more broadly than just planting. Supporting projects that combine plantings with improved substrate and retention brings a more durable effect and translates better into residents’ quality of life.
At One More Tree we also see that partnerships make the most sense when they include not only a one-time action, but the whole logic of “maintain the effect.” Supporting projects that combine plantings with retention and improved habitat conditions is more resilient to the realities of the city: downpours, droughts, heat, and rapid soil drying. This direction is also easier to communicate honestly, because instead of promising immediate change after one planting, it shows a real system: water stays on site, greenery has something to draw on, and residents feel the difference in comfort day to day.
Water as a resource, not a problem to remove
If we want urban plantings to stop being a seasonal event and become a lasting change, we must treat water as a resource, not a problem to remove. Trees do not only need a place in the ground. They need conditions that allow them to live in the city for years: healthy soil, space for roots, and water that does not escape into the sewer at the moment when it is needed most. Then greenery begins to work for real – for the climate and for people.
