Water Plants Care

Learn to buy, plant and maintain water plants that will thrive in your garden.
Aquatic Gardens

Aquatic Gardens

Photo by: DK - The Complete Gardener's Guide © 2011 Dorling Kindersley Limited

DK - The Complete Gardener's Guide , 2011 Dorling Kindersley Limited

Caring for aquatic plants is not difficult, and after planting many take care of themselves. Vigorous types may need dividing occasionally, and you will have to remove pond weeds.

Before planting a pond, check that your favorite plants suit its size and location. Put ponds and water features away from trees since these may cast too much shade for your plants to thrive. Fallen leaves also produce harmful toxins as they decompose in the water. Ideal plants for small ponds include marsh marigolds (Caltha palustris), SagittariaButomus, the corkscrew rush Juncus effusus f. spiralis, and dwarf water lilies, as well as the oxygenating plant hornwort. Larger, deeper ponds provide the conditions needed to support a greater range of plants, including many water lilies.

What to Plant Where

There are four main types of water-dwelling plants. To enjoy the benefits of all of them, make shallow ledges in the pond for marginals, which live at the water’s edge, and create an area of moist ground around the sides to accommodate bog plants. Ensure a depth of about 20 inches (50 cm) or more for aquatic plants, whose leaves float on the water’s surface, and include oxygenating plants, which either behave like aquatics or float in the water. Learn more about the four main types of water plants below:

  • Bog plants: These thrive in a moist or wet soil. There is a wide range available, which includes some of the most colorful waterside plants, such as several irises, primulas, Lythrum, and Lysimachia.
  • Marginal plants: Growing in a few inches of water, these plants soften the line between water and land. Some have colorful flowers (Mimulus), and many have dramatic foliage (Sagittaria).
  • Aquatic plants: These deep-water plants root on the bottom of ponds. There are relatively few plants in this group, but it includes water lilies, which require a minimum water depth of 20 inches (50 cm).
  • Oxygenators: Essential plants in a pond, oxygenators provide oxygen and absorb nutrients otherwise used by algae. Some, like Ranunculus aquatilis, flower above the water surface. marginal plant depth aquatic plant depth 

Pond Depths Explained

Plant labels state a preferred water depth, indicating where the plant needs to be set in your pond. The figure refers to the distance between the top of the root ball and the water surface. Place marginal plants that need to be at water level with the top of the plant basket level with the pond surface.

Keeping Water Clear

Weeds can ruin the appearance of a pond and compete with valuable ornamentals for light and nutrients. Help keep them in check by including oxygenating plants in your plan; these starve weeds of the nutrients they need to thrive. Check before buying to avoid introducing invasive oxygenators, since these can cause environmental problems by clogging up natural waterways if they escape from domestic ponds. In informal features you can also add bales of barley straw, which absorb nitrogen and starve algae.

If you have a contemporary pool with just a few plants and an expanse of clear water, you may want to use a commercial black dye designed for water features. The dye blocks the light, minimizing the growth of pond weeds.

Types of Oxygenators

Plants to include:

  • Ceratophyllum demersum (Hornwort)
  • Potamogeton crispus (Curly pondweed)
  • Orontium aquaticum
  • Cabomba caroliniana
  • Ranunculus aquatilis
  • Aponogeton distachyos

Plants to avoid:

  • Myriophyllum aquaticum (Parrot’s feather)
  • Lagarosiphon major (Curly waterweed)
  • Elodea nuttallii
  • Azolla filiculoides
  • Crassula helmsii
  • Hydrocotyle ranunculoides
  • Ludwigia spp. (Water primrose)
  • Pistia stratiotes (Water lettuce)

Eye-Catching Blooms

Some pond plants are demure and unassuming, offering a simple foliage backdrop, but some are beauty queens, prized for their eye-catching flowers. Water irises offer a fleeting splash of color in early summer, elegant arums add a sophisticated note to midsummer displays, while the dramatic scarlet flares of Lobelia cardinalis and fiery Mimulus appear later in the year. Uncover the water plants that will liven up your garden with this guide:

  • Iris laevigata: Japanese water irises come in shades of blue, purple, and white, and dress up ponds and water features with their elegant blooms, bulking out quickly to form large clumps, which you can divide easily to make more plants.
  • Mimulus: The monkey flower bears an abundance of small, red flowers (M. cardinalis) or yellow blooms with red throats (M. guttatus) among a mass of light green foliage.
  • Zantedeschia aethiopica: Arum lilies are among the most beautiful of all aquatic plants. The white types are the hardiest, while many rich pinks and purples are tender and need a frost-free home in the winter.
  • Lobelia cardinalisThis showy marginal is not hardy and needs to be overwintered indoors. The rewards for your trouble are 3 feet (1 m) spikes of brilliant red flowers from late summer to fall.

Aftercare and Maintenance 

Remove any dead or diseased foliage as soon as you see it to prevent it from polluting the water. In small ponds you can deadhead water lilies and marginals to keep your displays looking neat, but this is not strictly necessary. Although you can minimize weeds, some will inevitably find their way into your pond. Remove excess duckweed with a fishing net, and wind algae around a stick to pull it out. Leave the weeds on the edge of the pond for a day or two to allow trapped animals to return to the water. Dispose of aquatic weeds on a compost heap; never down a drain.

Top off the water levels of ponds and small water features regularly during hot summers. Check that any submerged planting baskets have not fallen off their supporting bricks—you may also need to remove bricks from beneath baskets of water lilies as they mature and the stems grow up to the surface.

If pests, such as aphids, slugs and snails, become a problem, lure natural predators, including frogs, toads, and newts, to your pond by creating damp habitats for them under stones or logs close by, and avoid pesticides. If plants become unruly or outgrow their planting baskets, lift and divide them in the spring. See maintaining pond plants for further information. Cut away any diseased or yellowing foliage, to maintain the appearance of your pond and to prevent the spread of disease.

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