Wood Around Pond . The new treated wood is not safe for ponds. Plant a variety of cacti and succulents in the spaces between the rocks and watch them grow. relaxingbackyardideaswithkoipond HomeMydesign from homemydesign.com The pond edging is something which you can take into account already during the design stage of your pond. Cattail roots can serve as filters, getting rid of toxins and excess nitrates in your pond. Wood is a widely available and versatile material that can be used in many ways in the garden.