Creating, maintaining and cultivating a food pond

What to understand before starting

• An available spot, ideally at a natural low point where water tends to gather.
• 5 to 6 hours of sun per day (enough light for aquatic life, no crushing full-south exposure that would make algae proliferate).
• Distance from large deciduous trees (dead leaves over-enrich the water and silt up the pond).
• Distance from pollution sources: roadside, runoff from sprayed crops, suspected old urban soils. A reinforced criterion for a food harvest.
• A rainwater harvester available for the initial fill and summer top-ups.

Detailed steps

1. Step 1

   Draw the tiered shape

   The secret of a stable pond is a stepped profile: a deep zone of at least 60 to 80 cm, ideally 80 to 120 cm (a refuge for the fauna against winter frost and summer heat); marginal shelves of 20 to 40 cm for the bank plants; and a gently sloping bank ('beach') on at least one side. This beach, where water meets land, hosts varied life and lets hedgehogs, birds and amphibians get in and out without drowning. Even a small pond works if it respects these tiers.

2. Step 2

   Choose the waterproofing method

   Three options depending on your soil and budget. Naturally present clay: if your soil is rich in clay, you can ram it (the gley technique) to make the bottom watertight, the most natural and durable solution, but it depends on the soil's nature. Bentonite: a swelling clay incorporated into the bottom to seal a leaking soil, a good compromise. EPDM liner: a flexible rubber, neutral for the fauna, that easily lasts 20 to 30 years (manufacturer data, Firestone, Carlisle), the most reliable option. Always protect it with a geotextile (felt) underneath and a thin layer of sand, to stop a root or a stone piercing it. Avoid PVC, less durable and less ecological.

3. Step 3

   Fill with rainwater, with clear eyes

   Fill preferably with rainwater. Tap water is chlorinated and above all loaded with nitrates and phosphates, which feed algae and unbalance the pond from the start. If you only have tap water, let it stand a few days before introducing the plants (the chlorine evaporates in 48-72 h). BUT beware: the science of 2020-2024 has challenged the idea that 'rainwater is pure'. The Cousins study (2022, Environmental Science & Technology) showed that levels of PFOA (a 'forever chemical') in rainwater exceed US drinking-water health advisories even in remote regions, and PFOS levels often do; microplastics and atmospheric heavy metals are also detectable. Rain remains preferable to the mains for the pond, but the word 'impeccable' should be used with measure. See the 'Rainwater quality' concept for the detail.

4. Step 4

   Plant by tiers, native oxygenators first

   Submerged oxygenating plants are essential: they produce oxygen and compete with algae. Favour hornwort (Ceratophyllum demersum) or spiked water-milfoil (Myriophyllum spicatum), native species. Absolutely avoid the invasive exotics banned by EU regulation 1143/2014 and the French order of 14 February 2018: water primrose (Ludwigia grandiflora and L. peploides), Crassula helmsii, Nuttall's waterweed (Elodea nuttallii), parrot's-feather (Myriophyllum aquaticum). Add floating plants (dwarf water lily, a controlled amount of duckweed) to shade the surface, and bank plants on the shelves (yellow flag iris, water mint, cattail in a container).

5. Step 5

   Aim for a vegetation balance of a third to a half

   Aim in the long run for a third to a half of the surface covered by vegetation: it is the balance that limits the light available to filamentous algae, without smothering the open-water zone the fauna needs.

6. Step 6

   Be patient, life comes on its own

   A pond takes one to two seasons to find its balance. Life comes on its own: dragonflies in a few days, amphibians in a few weeks, birds as soon as insects appear. Never introduce goldfish (Carassius auratus), they devour amphibian larvae and eggs and cloud the water. Nor introduce plants or animals taken from a wild pond, a health risk and a regulatory risk.

7. Step 7

   To grow edible cattail: submerged basket + impeccable water

   Always plant the cattail (Typha latifolia or T. angustifolia) in a submerged basket or container, openwork pond baskets lined with jute, set on the marginal shelf 10-30 cm below the surface. You thus control its spread and can harvest it cleanly. For a food harvest, the pond must be fed with rainwater and away from any contamination source, see 'mistakes to avoid'. The ideal alternative: a separate basin dedicated to cattail (a reed-bed zone or watertight tank), both for controlled harvest and for its purifying qualities.

What is the minimum size for a pond to work?

There is no strict minimum size: the larger a pond, the more wildlife it draws, but even a very small pond gives a home to plenty of small creatures (RHS). The profile matters more: depths that vary gradually and at least one gently sloping bank (RHS; LPO Auvergne-Rhône-Alpes).

Do I need a pump or a filtration system?

No, not for a natural pond. Filtration is only needed if you introduce fish (not advised). A balanced ecosystem with its oxygenating plants, its bank vegetation and its fauna regulates itself without energy.

Can you eat the other pond plants?

Water mint (Mentha aquatica) is edible under the same precautionary conditions as cattail, impeccable water required. Yellow flag iris, water lily: not edible, to be left for biodiversity and beauty.

How long before you can harvest cattail?

Count 2 to 3 years from planting to have rhizomes developed enough to harvest without exhausting the plant. The young shoots ('Cossack asparagus', a traditional name documented by Couplan) and the pollen can be taken from the second season.

Does the pond attract mosquitoes?

A balanced pond attracts no more mosquitoes than a forgotten bucket of water, on the contrary: mosquito larvae are devoured by dragonfly larvae, newts, backswimmers and several species of aquatic beetle. Ponds with goldfish or stagnant lifeless water attract many; living ponds host few.