A New Hampshire lake at sunset


healthy aquatic vegetation nh lakesAquatic plants are a common sight in New Hampshire’s lakes.

Most of our lakes have a few dozen different types of plants growing in them. And, most plants are good for the health of the lake and the animals that live in and near the lake.

A diverse mix of plants rooted in sediment, growing out of the lake, and floating on the surface provides a great food source and habitat for animals. Plants also put oxygen into the lake for fish and other organisms and they remove waste gases.

Did you know that algae is a plant, too?! These microscopic plants make up the base of the food chain in lakes, providing food for tiny microscopic animals and small fish.

Sometimes plants can become too common in the lake.

The excessive growth of plants in lakes can interfere with human activities. While property owners may manage small areas of plant growth to provide access to swimming areas or docks, the removal of large areas of plant growth is not good for our lakes. And, to remove large areas of plants, a state permit is required.

However, lakes are not meant to be sterile and plant-less like swimming pools. The removal of beneficial natural plants may allow harmful invasive plants to spread in the lake and may cause algae blooms and toxic bacteria blooms.

The best way to prevent too many plants from growing in the lake is to minimize the amount of phosphorus that flows into the lake. Phosphorus is the main nutrient that plants need to grow. By fixing eroding areas and soaking up runoff water on the landscape, limiting the use of fertilizer on lawns, and ensuring that septic systems are working property, the amount of phosphorus in the lake will be minimized.

Unfortunately, not all plants are good for the lake.Lake Host AIS Identification 2019 Page 1

Plants that are found in our lakes, but are not natural to our lakes, are called invasive species. The main way invasive species spread from other regions and countries into our lakes is by traveling on boats, trailers, and recreational gear that has not been properly cleaned, drained, and dried between uses.

Invasive species do not have any natural predators, causing serious problems in the lake. Not only can they make recreation difficult and dangerous for people, they can outcompete natural plants and animals for food and space.

Click on the image to the right to view and download our Aquatic Invasive Species Identification Flyer.

Wondering what plants are in the lake?

The New Hampshire Department of Environmental Services (DES) offers a reference guide for common plants and algae found in our lakes. To access this guide, click here.

DES biologists map the plant growth in our lakes on a long-term, rotating basis. For maps, click here.

Hundreds of volunteers throughout the state are trained how to monitor and identify plant growth lakes through the DES Weed Watchers Program. For more information, click here.

If you think you have discovered a new growth of an invasive plant in a lake, contact DES at (603) 271-2248 or email amy.smagula@des.nh.gov.