[Ebook] Encyclopedia of Aquarium & Pond Fish – Directory of Pond Plants – Oxygenators

Directory of Pond Plants

Oxygenators

These plants, which grow beneath the water’s surface, play a crucial role in creating a healthy environment for pond fish, because they release oxygen into the water as a by-product of photosynthesis. They also help to maintain water clarity by competing for dissolved nutrients with particulate algae (which are responsible for the green hue of pond water). Some species also produce highly attractive flowers. Oxygenators can, however, become rampant, and it may be necessary to remove clumps to ensure that the fish have adequate swimming space.

Water Crowfoot (Ranunculus aquatilis)

• ORIGINS: Occurs naturally in parts of North America and Europe.
• SIZE: Grows in clumps up to 3 ft (1 m) in diameter.
• WATER: Grows well in both flowing and still water. Hardy to –20°F (–29°C).
• PROPAGATION: Take stem cuttings during the growing season, or sow seeds in late summer.

This member of the buttercup family has two leaf forms: finely segmented leaves that grow underwater, and broader ones that float on the surface. Its flowers, which are white with bright buttercupyellow centers, are often held above the water. As with other oxygenators, cuttings of Water Crowfoot can be rooted in containers set on the pond floor. Start them off on the marginal shelf (see p.364) and then move them to deeper water.

Eurasian Water Milfoil (Myriophyllum spicatum)

• ORIGINS: Grows widely in parts of Europe, Asia, and North Africa; a similar species exists in the US.
• SIZE: Strands may reach 10 ft (3 m) in length.
• WATER: Plant up to 3 ft (1 m) deep, in brackish and fresh water. Hardy to –30°F (–34°C).
• PROPAGATION: Take stem cuttings from established plants in spring or summer.

Eurasian Water Milfoil spreads rapidly, forming dense thickets that look attractive in shallow water. Its delicate whorls are usually green but sometimes have a reddish hue. The plant may produce small yellowish-white flowers during summer. Eurasian Water Milfoil is an invasive plant that can clog rivers and lakes with dense mats of vegetation, and it should never be released into natural waterways.

Canadian Pondweed (Elodea canadensis)

• ORIGINS: Naturally occurs in North America, but now established in Europe.
• SIZE: Strands can easily grow to 12 in (30 cm) or more.
• WATER: Thrives in clear water in a sunny position. Hardy to –20°F (–29°C).
• PROPAGATION: Break off pieces about 6 in (15 cm) from the growing tip. Does not need to be planted.

The relatively small, dark green leaves help to distinguish Canadian Pondweed from similar species. Pondweed grows readily, especially during the warmer months of the year, and is sufficiently hardy to survive the winter outdoors in temperate areas. Pondweed is sold as sprigs that simply need to be attached to a weight so that they sink to the bottom. The sprigs will soon start to grow and provide a valuable refuge for young fry.

Common Bladderwort (Utricularia vulgaris)

• ORIGINS: Widely distributed in temperate parts of Europe, Asia, and North America.
• SIZE: Stems reach 6 to 18 in (15–45 cm) in length.
• WATER: Prefers relatively calm water in a sunny position. Hardy to –30°F (–34°C).
• PROPAGATION: Remove young plantlets from an established plant during the growing season.

This slow-growing, rootless carnivorous plant has bladderlike structures among its foliage; as well as providing buoyancy, they also trap tiny aquatic creatures, including newly hatched fry. In summer, it produces a cluster of yellow flowers held above the water on a strong stem. Bladderwort may become choked by blanketweed (see p.319).

Hornwort (Ceratophyllum demersum)

• ORIGINS: May have originated in Asia, but now occurs throughout temperate regions of the world.
• SIZE: Stalks may reach up to 24 in (60 cm) in length.
• WATER: Not fussy about water chemistry; grows well in both sun and shade. Hardy to –10°F (23°C).
• PROPAGATION: Break up the stems of established plants during the growing season.

The unusual name of this plant originates from the distinctive broad shape of its growing tip, which is reminiscent of a cow’s horn. Hornworts do not root, but if in contact with a substrate, the leaves will start to anchor the plant in place. Over the course of the growing period, hornwort forms long strands. As the leaves start to die back, the budlike tips of the strands drop off (or can be cut off) and sink to the bottom of the pond, and it is from these buds that new plants will develop the following spring. By the end of the growing season, Hornwort becomes very straggly, so it is best to pull out the plants at this stage. Hornwort is strictly aquatic and dies back if exposed to the air for any length of time. It is also fragile, and breaks easily when handled.

Willow Moss (Fontinalis antipyretica)

• ORIGINS Widely distributed in parts of Europe, Asia, North Africa, and North America.
• SIZE Stems can grow to a length of 20 in (50 cm).
• WATER Prefers clear water, but tolerates either sun or shade. Hardy to –30°F (–34°C).
• PROPAGATION Break off branches from established plants and attach them to submerged objects.

Although this hardy moss does not flower, it has an attractive appearance. It fares best in ponds free of filamentous algae and is particularly suited to areas around waterfalls, since it naturally occurs in fast-flowing streams. Willow Moss will attach itself by its roots to submerged objects, such as planting containers and rocks. Hold pieces in place with a rubber band until the roots get a firm grip

Water Violet (Hottonia palustris)

• ORIGINS: Found naturally in the wild throughout much of Europe.
• SIZE: Can grow to a height of more than 3 ft (1 m).
• WATER: Thrives best under acidic water conditions with a pH of 6.0–6.5. Hardy to –20°F (–29°C).
• PROPAGATION: Divide clumps during the growing season, or take cuttings.

Despite its name, this plant is not related to the violet but actually belongs to the primrose family. The large surface area of Water Violet’s fine foliage makes it a valuable oxygenator. During summer, plants develop flower spikes that stand more than 12 in (30 cm) above the water’s surface. The leaves on the flower spikes are more compact than the fine, feathery foliage that Water Violet displays on its submerged parts. The flower color itself can be quite variable, ranging from white through pinkish-lilac to blue. As the flowers fade, the flower stems falls back into the water, and the seedheads develop. Water Violet dies back naturally in the fall, when the plants form so-called winter buds, or turions, from which new plants will grow again the following spring. Although Water Violet is hardy, it tends to thrive only in clear water, and it will be adversely affected by any buildup of filamentous algae in the pond.