Keeping a pond healthy is critical to its success. To maintain a functioning ecosystem, a backyard water feature requires occasional plant thinning or dividing, which should initially be done just as the water warms up after winter. This particular backyard water feature maintenance should continue as needed throughout the entire growing season: as long as the water is above 60°F.
Pond plants rooted in rocks on the bottom of an organic backyard water feature spread more vigorously than those confined in containers set on concrete pond bottoms. Once established, pond plants may cover the entire water surface within several years. Such abundant greenery, although lush to look at, inhibits water circulation. This, in turn, reduces the effectiveness of the pond's biological filtration and skimmer system that maintains the clear water in your backyard water feature.
When more than 50-70% of your backyard water feature’s surface is covered by pond plants —whether the plant roots have spread naturally or are restricted by pots—it is time to thin or divide them.
Mid to late March is prime time to perform this task initially for the year, because pond plants are beginning their growth cycle and will recover quickly. AND, the pond water has warmed sufficiently to be comfortable to step into, but hasn't become so warm that maintenance threatens fish health.
Disturbing a backyard water feature stresses your fish, and parasitic activity increases as water temperatures climb. The combination of those two things are dangerous to larger Koi. Smaller Koi and goldfish handle the stress much better. Finally, don't thin plants during the cooler fall and winter months, when they are dormant, as this could cause them to die back and rot, in turn causing major water quality issues with your backyard water feature.
Thinning Plants in a Phoenix Pond
Many species of pond plants can be thinned by pulling or digging out the excess, root and all. Wear a sturdy pair of neoprene gloves to protect your hands. You may replant the excess in other areas of your backyard water feature, compost them, give them away or trade them with other pond owners, or simply discard them. Such plants that you might find in an Arizona backyard water feature include Pennywort (Hydrocotyle verticillata), Rush (Juncus sp.), Water Clover (Marsilea sp.), Yerba mansa (Anemopsis californica) and Taro, also known as elephant's ear (Colocasia escutenta). Any of these can become quite prolific if left unchecked.
Dividing Plants in a Phoenix Pond
Other species of pond plants need to be lifted and divided, similar to perennials. These backyard water feature plants might include Taro's black varieties ('Black Beauty', 'Black Magic', 'Black Ruffles') and 'Illustris.’ To divide a pond plant, carefully dig up the entire root ball (or lift it from its container, if applicable). Remove any excess soil so that you can see the rhizomes: horizontally growing underground stems from which new shoots and roots will sprout.
Cut and divide the clump with bypass pruners so that each new section is left with at least 3” of healthy rhizome with growing tips. Healthy pond plant tissue will be firm and bright white. Trim and discard any mushy or brown material, which are signs of rot. In addition to the Black Taro varieties, pond plants in your backyard water feature that require division include Canna, Iris, Pickerel (Pontederia cordata) and Water Lily.
Re-Planting Plants in a Phoenix Pond
Replant rhizome sections in the backyard water feature’s rock bottom, and then anchor them with a handful of pea gravel to prevent your voracious fish from uprooting them, or replant in the dirt containers. For heavy feeders, such as Iris, Taro and Water Lily, you can tuck a slow-release fertilizer tablet next to the roots. Only use tablets formulated for pond plants and follow package instructions. Nutrient overload encourages algae bloom, so don't be tempted to over-fertilize!
Not comfortable with doing it yourself? We can help! Contact us at 623-572-5607, via Email, or simply fill out an Annual Cleaning Request Form, or sign up for one of our No Worries Maintenance Programs.
The video below is an excerpt from our Annual Cleaning Clinic on how to transplant an aquatic plant in a Phoenix pond.