August 24, 2026, 4:46 am | Read time: 7 minutes
A sponge garden absorbs water when it pours and holds on when not a drop falls for weeks. Discover the design concept behind it, the elements involved, and why often just a shovel is needed, here on myHOMEBOOK.
Overview
What Is Behind the Concept of Sponge Gardens?
Imagine pouring 6,000 watering cans filled with rainwater into the sewer system, year after year. That’s essentially what happens if your roof is about 100 square meters and the rain falls normally. A sponge garden reverses this equation: It retains some of this water on the property instead of letting it simply drain away.
Driven by the climate crisis, heat waves, drought, and heavy rain are intensifying, putting every garden under pressure. Sometimes there’s too much water, and sometimes far too little. Balancing this imbalance in one’s own green space is a mystery for many garden owners. Often, an underground cistern seems to be the only solution, but it’s complex and expensive. Sponge gardens prove: It can be done without buried containers and heavy technology. What matters is design. Sponge gardens utilize the garden’s topography. Gravity works for free, the soil filters for free, and deep-rooted plants draw the buffered water back up when everything above dries out.
A Matter of Design
The sponge is the program’s namesake. The garden is meant to absorb rainwater first and release it later. This principle is already used in many cities. Appropriately designed areas are intended to prevent sewers from overflowing during heavy rain and flooding tunnels, basements, or streets. Similarly, they prevent street trees from drying out in the heat because their root space never fully saturates.
“A sponge garden is nothing more than the idea of sponge cities applied to gardens. Water is no longer seen as waste to be quickly disposed of but as a resource. Since climate change has been on our backs, I’ve been deeply involved with it,” says landscape architect and author Jens Maute, who won the German Garden Book Prize 2026 for best guide with his book “Clever Water Management in the Garden.”
Understanding rainwater like apples or potatoes as a potential harvest is the core idea of U.S. permaculture expert Brad Lancaster. His motto: “Slow it, spread it, sink it.” The elements that make a garden spongier follow this principle: They use the soil as storage and keep the water in the regional water cycle.
Many Factors Are Important in Implementation
In practice, sponge gardens rarely rely on a single measure. Usually, several elements work together with the soil and planting to make the garden spongier. Almost always, a slope plays a role, even if it’s not immediately visible in the garden. “Very few gardens are truly level. Even a tiny, barely visible slope is enough to gently direct water,” explains Maute. You can test this simply: Pour a liter of water at two or three spots in the garden and observe where it flows. For more precision, use a water level.
The Basin: The Easy Entry Into Sponge Gardening
The simplest method is the basin: a shallow depression, ideally where water already collects during rain, at least three meters from the house—more for older buildings with sensitive foundations, like sandstone cellars. “You dig a minimal bowl shape, about twenty centimeters deep, and direct the roof water into it to let it slowly seep in,” says Maute. Even simple lawns can be effectively used this way.
For more, plant the basin with species that tolerate both drought and brief flooding. Marsh marigold, purple loosestrife, meadow cranesbill, or yellow flag iris are recommended by Maute. All are robust, native perennials. Edible plants like rhubarb, Swiss chard, or Jerusalem artichoke are also suitable for planting in infiltration basins, as are young trees. Some call such a planted basin a rain garden, but there’s no fixed terminological distinction.
Contour Trench and Mound: More Control Over Water
An advancement of the basin is the contour trench. In its simplest form, it follows the slope line horizontally: The water doesn’t move but stays put and seeps in. However, if you give the trench a slight slope of one to three percent, the water moves, albeit with a speed limit. Water is lazy—left to itself, it rushes straight down, taking valuable soil with it. The gentle slope forces the rain to take a slalom course. The water meanders gently from station to station to where you want it.
Where feasible, you can connect multiple basins or trenches along the slope: Once the top station is full, excess water is directed to the one below. This creates a small network that distributes larger amounts of rain instead of letting it seep in at just one spot. For an extra step, combine basin and mound: The excavation from the depression is piled up right next to it, so nothing needs to be transported away. Herbs or drought-tolerant perennials thrive on the dry mound, while plants with higher water needs grow in the wetter basin. This also creates more visual variety than a traditional lawn ever could.
What Exactly Is Drainage for Plants?
4 Methods for Collecting Rainwater in the Garden
Creating a Sponge Garden: Effort and Costs
The cost depends entirely on how much you want to do yourself. At the low end, a shovel is enough.
A basin costs nothing but time: dig out the soil, plant if desired, and you’re done. If you already have a spot in the garden where rain naturally collects, there’s even less work. The only requirement: The soil itself must cooperate. Sandy soil lets water through quickly, clay soil stores much more, and loam stores the most—up to 45 percent of its volume. But that’s not helpful if the water is trapped there: Loam holds it so tightly that roots can hardly access it. Humus can offset this disadvantage: It stores many times its weight in water and releases it, unlike pure loam.
A bit more expensive, but still affordable, is a rain collector for the downspout, available for around 50 euros at hardware stores. “As long as the target isn’t higher than the rain collector itself, no electricity or pump is needed. The water flows simply to where I lay the hose, and gravity does the rest,” says Maute. For it to work long-term, check it regularly for moss and leaves. However, there’s a catch to watering with the rain collector: You have to go out when it rains—saving water in a raincoat. But you can direct the water specifically to a basin, a thirsty hedge, or a tree disc. For more storage without digging, use an IBC container: a thousand-liter plastic tank, often a cheap recycled product from industry, which can even be stacked if needed.
At the high end of the cost scale is the cistern: an underground storage that quickly costs as much as a premium garden house, more sensible for new constructions where it can be planned from the start. In existing gardens, the effort often doesn’t justify the benefit.
Small Gardens Can Also Become Spongy
Even properties where you can barely fit two deck chairs side by side can become spongy. A soakaway needs hardly any space: Use a simple earth auger to drill a hole up to one and a half meters deep. Filled with gravel, grit, or sand, it channels rainwater into the depths. “A sponge garden, no matter how small, is a cell of the sponge city. Disposing of water via the sewer is absurd. We do it anyway and then complain that we have none left. We really need to rethink this,” says Maute.