What's Growing in my Pond??!! - Part 1

Blue-green algae bloom (Held)

In mid- to late-spring each year, I receive a few calls on controlling pond vegetation.  However, this year these calls have been coming in about a month early (just like everything else) and with seemingly greater frequency than recent years.  Just as grass and weeds in the lawn have been thriving this spring, so has pond vegetation.  And from what I have seen so far, "thriving" is an understatement. 

Blue-green algae bloom, closeup (Held)

Proper management of pond vegetation is crucial, especially in years like this when unimpeded early, rapid growth could spell trouble for pond ecosystems later this summer.  This post will deal specifically with preventive control methods, the first step in controlling pond vegetation.  In a later post, mechanical, biological, and chemical controls will be covered.     


American pondweed (APM-3)

While it may be tempting to achieve a sterile, swimming pool effect in a pond, this is not a desirable outcome. The goal of a good aquatic plant management plan is to achieve a balance between too much vegetation and too little vegetation. Some plants, particularly native species, are highly desirable and add interest and appeal to the pond. But how is this balance achieved? The best way to achieve balance is the careful use of one or more management methods, including preventive, mechanical, biological, habitat alteration, and chemical methods.

Many pond weeds or their seeds are carried into a body of water by wind, birds, fish introduction, boat trailers, fishing, etc. Prevention starts with reducing or eliminating the causes of the spread; i.e. discouraging geese from visiting your pond, washing plant fragments off boat trailers and boats before moving to a new site, and removing plant fragments when moving fish or fish bait from one site to another.

A newly introduced weed will become a problem only if water conditions are just right. Good growing conditions usually mean the body of water is shallow or has shallow areas with good light penetration, and has an available source of nutrients (nitrogen and phosphorous) either in the water or stored in the sediment. Often nutrients enter a pond from runoff or stream flow. In addition to monitoring and reducing or eliminating nutrient and sediment sources in the watershed, the following steps can be taken to help prevent weed growth.

First, do not fertilize the pond or lake. In the Midwest, most waters are sufficiently rich in food organisms to feed large fish without being fertilized. Next, maintain a good sod and grass cover around the pond or areas that drain into the water. This will help absorb nutrients that might flow into the water as well as help control erosion. It is also thought that taller vegetation around a pond reduces the chances of Canadian geese colonizing a water site. A third step is to not apply fertilizer within 20 feet of the bank.

Livestock should not be given access to the pond except in cases of extreme heat stress. If the pond is used for livestock water, it should be fenced and the animals should be used watered using a stock tank outside the pond. Animals can add turbidity and fertility to the water and tear down the banks. It is also important to make sure run-off from feedlots or other livestock pens does not run into the pond.

Finally, a settling or retention pond or wetland area can be established to receive and settle out nutrients before the flow reaches the main body of water.

Stay tuned for Part 2.........