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Brooklyn Greenbridge

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High School Activity: Washtub Pond

Goal:

To help teens see water as important in the garden and to give them an opportunity to create a water-garden corner in the garden.

Time:

Allow 2-1/2 hours.

Materials:

In advance:

  1. If you use a metal tub and you paint the tub on the day of the pond-digging, it will still be wet and you will not be able to fill and plant it. Therefore, do the following at least 24 hours before the workshop:
    • Prime the tub by scouring it and rubbing it with vinegar.
    • When the vinegar has dried, paint the tub with the blue enamel paint. (At the hardware store, explain what you'll be using the paint for so that they will steer you towards the proper paint. They may also have ideas for additional treatments that can slow rust.)
  2. At least four days before your workshop, if your garden has a rain barrel, fill it with water. Stir it daily. This will allow chlorine in the water to evaporate. The chlorine may otherwise harm plant and animal life. You can also simply fill recycled gallon jugs with water in advance.
  3. Go to a nearby pond at a park or botanical garden and scoop up a cup of duckweed (be sure to get permission first). Duckweed is the small, floating plant that lives on the surface of many ponds. When your pond is filled, you can pour the duckweed in. It will spread, shading the surface of the pond and keeping the water temperature lower, reducing algae problems.

Activity sequence:

  1. In a group, explain that you are going to build and plant a small pond garden. Ask:
    • What is water used for in the garden? (watering plants, keeping cool, providing drinking water for wildlife)
    • Why do people like water gardens?
  2. Show the group the tub and explain that you are going to sink it in the ground to create a small pond. Explain how you have treated the tub in preparation.
  3. Show the site you and your garden group have picked, explaining why.
  4. Explain the steps in building the pond and then set the group to work:
    • Dig a hole deep enough to hold the tub. Even out the bottom of the hole with sand, soil or gravel, so that the tub sits in the hole with the rim about 1 inch higher than the ground. (Set a board across the tub and place a level on it to see if the tub rests evenly.)
    • Fill in with soil around the sides of the tub.
    • Dig down a few inches around the tub and line the border with rocks or bricks, extending this surfacing out in one or all directions for a patio-like effect. Fill the spaces between the stones or bricks with sand.
    • Fill the tub with water. Overfill it and ask the children to watch for where water runs off. During heavy rain, this is where the pond will drain. You may want to put gravel and rocks along the course that the run-off water will take. If it takes a route that is disruptive to your garden beds, dig a small channel to guide the water in another direction.
  5. Finally, populate your pond. Because the pond is so small and does not have circulating water, it will be difficult to maintain a balanced system. Tadpoles are adap and can survive less s ponds. The plants mentioned above, duckweed and cabbage plant, will also do well. In any event, you may want to discuss the factors at play in regular ponds (see background information, below). After discussing these factors, do the following:
    • submerge the aquarium plants,
    • pour in the duckweed and
    • add the tadpoles.
    Bear in mind that the pond will require ongoing care and maintenance, including emptying, cleaning and refilling. Working to maintain it as a living system is an exciting longterm project that some children in the group may want to take on.

Background information: