Healthy Ponds 101

Healthy Ponds 101
Posted on 06/22/2023

On a stroll through a city park, many enjoy admiring the picturesque plants blooming in our ponds. But others often ask: Should there be so many plants crowding the water?

Healthy pond plants

Aside from our larger lakes, like Lake Lenexa or Mize Lake, most of the ponds owned by the City are managed for water quality instead of recreation. That’s why you’ll see a lot more plants in these ponds and less open water.

Ponds go through several seasonal cycles each year. During the summer months, the pond may have rapid growth of algae and aquatic vegetation. This is actually a positive sign of a healthy pond ecosystem! The plants help to clean the water before it leaves the pond and chemically balance the water quality. They also provide habitat for fish and serve as a food source for animals that live in and around the pond.

Examples of healthy pond plants include duckweed, water lily and water primrose.

Our staff monitor plant growth in all city-owned lakes, ponds and streams. When they determine that growth is excessive, staff manually removes the plants.

Unhealthy pond plants

Certain non-native species of aquatic plants are extremely aggressive and invasive. In large quantities, they can pose a threat to the pond ecosystem

You may notice more algae in August and September, when hot, dry, periods encourage its growth. An overabundance of some algae species can be dangerous to people and pets. If you see signs posted that say a harmful algae bloom is present, follow their directions carefully.

Examples of unhealthy vegetation include curly-leaf pondweed and blue green algae.

Algae blooms can develop rapidly and may move around the pond, so use your best judgement if you spot suspicious vegetation. Scum, foam, paint-like water surface or bright green water can be signs of harmful algae.

If you think you see a harmful algae bloom, keep everyone, including pets, from entering the water. You can report the bloom to state officials at or 785.296.1664.

There isn’t much that can be done to remove algae. The best course of action is to wait for rain to dilute the water and flush out the algae.

Protect ponds at home

The best way to prevent harmful algae blooms it to limit the amount of excess nutrients that enter streets and ponds. The most common source of excess nutrients in our water is one you’re probably using at home: fertilizer.

If you’re using fertilizer:

  • Follow the instructions carefully, and use it sparingly.
  • Make sure you’re using the right fertilizer by getting a soil test. It will show which nutrients your lawn really needs.
  • Never use lawn chemicals before heavy rain is expected.
  • Use a phosphorus-free fertilizer. Phosphorus is a significant nutrient pollutant.
  • Be cautious when fertilizing on slopes and lawn edges to prevent the chemicals from washing into nearby storm sewers.

You can also try these ways to minimize your garden’s need for fertilizer:

  • Mulch mow. Leaving your grass clippings on the lawn can return up to 25 percent of its needed nitrogen.
  • Use compost or natural lawn chemical alternatives.
  • Landscape with native plants, which are naturally adapted to thrive in our climate. They reduce or eliminate the need for fertilizers, watering or pesticides.

DID YOU KNOW? There are more than 260 ponds in Lenexa, and the City owns and maintains 12 of them. The rest are cared for by the property owner.

Published June 22, 2023