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Self-watering planter from recycled soft-drink bottles (膠樽廢物利用, 不用日日淋水,慳水環保種植方法 ) - Updated on 10 December 2009

What follows is a way for making your own self-watering planter. This self-watering planter uses the well-known capillary effect to maintain a steady stream of moisture for the plant growth. With this self-watering planter, you don't need to water your plant every day.

This planter is not difficult to understand. Basically, it comprises a water reservoir and a soil container. Between the water reservoir and the soil container, there is some type of wicking structure that wicks water out of the water reservoir. The wicking action, together with the evaporation effect due to the sun heat, draws the water from the water reservoir up into the soil. As a result, the soil contines to be wet without running into a waterlogged situation.

1. Materials required: a pair of sissors, a wire cutter, a soft-drink bottle, a plant, a few pieces of kitchen towels, a few cotton strings.

2. Use a pair of scissors to cut the soft-drink bottle into two halves --- that is, the upper half and the lower half. Be careful, don't cut yourself.

3. Use the wire cutter to create an opening on the bottle cap. This opening should be large enough to accommodate a wicking structure, which, in this case, is a piece of kitchen towel.

4. Insert about two cotton strings into the mouth of the soft-drink bottle. Herein, the cotton strings is referred as wicking structure.

5. Position the bottle cap in a way that the side opening of the bottle cap fits the wicking structure. Then, screw the bottle cap on tightly.

6. Use a thumbtack to puncture as many holes around the bottleneck as possible. This step is highly important, because the root system of your plant will need to breath. Without enough holes around the bottleneck, your plant can die of lack of oxygen and get root rot.

7. Pour water to the lower half of the soft-drink bottle to 1/2~1/3 full.

8. The next step is to turn the upper half of the soft-drink bottle upside down and place it onto the lower-half, with the bottle cap pointing downward. Now, the wicking structure should be partially immersed into the water.

9. Before filling any soil, add another piece of kitchen towel into the upper half of the soft-drink bottle. At this stage, you can even cover the base of the soil container with compost teas dry leaves and other dry kitchen wastes.

10. Add some soil or purchased potting mix:

11. Sow your seed or transplant your plant.

12. Fill the planter with more soil, trim off the rest of the kitchen towel which remains on the edge of the planter and soak the soil with water:

32. There is no need to water the plant unless the water reservior is running out of water. If there is not enough water left in the water reservoir, then add some water onto the soil. The excess water as a result of over-watering will eventually drain off into the water reservoir, but most of the fertilizers and other important minerals will not get carried away. After serveral days, the wicking structure will draw water up again.

Notes:

a) The cotton strings absorb water through capillary action. The capillary action that moves water up into the soil is subjected to the resistance due to the gravity. It is important to plant your plant as deep as possible so that the root can readily access the moisture. However, planting your plant in too deep will encourage stem rot.

b) If you don't have any platistic bottle, then find one from the nearby rubbish bin.

c) If you don't have any cotton strings, then use kitchen towels, shoelaces, pieces of scrap cloth, old newspaper or whatever similar.