Ponds are a wonderful addition to any garden. They are beautiful, encourage wildlife, improve your microclimate but most of all they are an excellent way to, very simply, grow an abundance of edible food. Delicious salad green such as Lebanese Cress, Water Parsley, Native River Mint, Water Celery and Kangkong thrive in water. Medicinal plants like Brahmi are water plants. While Water Chestnuts, Arrowhead and Vetiver all love growing in water. Where to start? If you have the room, cast iron bathtubs and IBCs cut in half make excellent food ponds. A few things to bear in mind for a pond system. Most food plants will grow best when partially immersed. This can be achieved by stacking bricks in the bottom of your container and placing the potted plant on top. Mosquitos are another important consideration. Placing even a couple of fish in your bathtub can control mosquito larvae. A combination of emergent (i.e. Lebanese Cress, Water Parsley, Native River mint), surface (i.e. native azolla or duck weed) and submerged (ribbon weed) plants will help you achieve a balanced system. If you have fish, ensure that you have at least 1/3 of the water surface free to allow adequate oxygen transfer. Pond will thrive in full sun so long as they are regularly topped up. Aim to refresh 10% of the pond volume at a time, refreshing the entire volume gradually over the period of 1 month. This is important to prevent stagnation and the excessive build up of algae.
It’s amazing the difference a little bit of permanent water makes to the feel of a place. We have several frog ponds around our emerging food forest. Some of the simplest (and most cost effective) ponds can be made using cast iron bath tubs half filled with old bricks (we avoid holes with plastic lining as we also grow edible plants in the ponds). Reeds (native Juncis or similar) are then added to the pond in pots with a layer of gravel over the surface of the soil to weigh the pots down and keep the soil in place. The addition of floating aquatic plants such as Azolla pinnata (Australian native) on the surface of the pond makes it safe for bees and other insects to get a drink. A few small native fish such as Crimson Spotted Rainbow Fish (Melanotaenia duboulayi) are also an excellent addition to ponds for the control of mosquito larvae. For these ponds we’ve also added a few cut sleepers around the top but large flat rocks obviously work really well to disguise the tubs too. If you don’t have a large tub try nestling a bucket in a pile of mulch and adding some aquatic plants. The effect can be surprisingly good.