American frog’s-bit (Limnobium spongia)
Zones: Eight to 11.
Exposure: Full sun to part shade.
Frog’s-bit has small, spiny-type flowers in mid to late summer, although the dark-green, spongy floating leaves are what makes this plant attractive. If the NSP includes fish, be aware as they may nibble on the outer edges of the leaves.
Water lettuce (Pistia)
Zones: Nine to 11.
Exposure: Part sun to part shade.
Water lettuce has lush, lime-green leaves arranged in spirals. This tropical floater is highly susceptible to frost, but makes a great summer addition for large NSPs to small bowls.
Salvinia natans (Large Salvinia)
Zones: Nine to 11.
Exposure: Part sun to full shade.
This unique aquatic fern grows in whorls of three leaves, each bearing fine silky hairs. Not readily eaten by fish, Salvinia natans provide near-perfect surface cover.
Salvinia rotundifolia (Small Salvinia)
Zones: Nine to 11.
Exposure: Part sun to full shade.
A smaller, more round form of Salvinia, this floating fern grows in less defined sections and seems to free-float more than its larger counterpart.
Planting water lilies and winter-hardy water lilies
Each lily should have approximately 1 m (3.2 ft) for growth and sustainability. Prior to purchasing, determine if the species selected spreads quickly or is less expansive. If stunted growth is desired, this can be done by building up stones fist-or head-high around a water lily bed to hinder its expansion. More than 450 varieties of water lilies are on sale worldwide. Of course, not all are ideally suited to every climate. Therefore, choose types that have been raised for generations in the climatic zone where they are to be planted.
Hardy water lilies are defined as water lilies that can tolerate winter temperatures provided the rhizome itself does not freeze. Six main colour varieties dominate the hardy water lily landscape: red, pink, white, yellow, peach/orange, and changeable. Most varieties can be traced back to a cold-water Nymphaea native to mountain lakes in Sweden. As such, these particular water lilies are extremely tolerant of temperate climates and grow very well in zones four to 11. From spring to fall, single flower buds—often many per plant—will rise from the base. Like clockwork, opening mid-morning and closing at night, these flowers last three to four days and are continually replaced by new flower buds arising from the depths.
The underwater plants
Underwater plants as the name suggests are well-suited to the aquatic environment; the stems and leaves are flexible and have air chambers that lift them. With their entire plant body, they take nutrients directly from the water, serving mainly to anchor the plants to the bottom. Submersed plants are the best nutrient competition for algae and give off various materials that halt algae development (alleopathy). These underwater plants should be found in every pond, since they do the following ‘jobs:’
- Biogenic decalcification;
- Oxygen enrichment of the water;
- Nutrient competition for algae;
- Space competition;
- Binding of phosphates and other nutrients;
- Growing surface for biofilm; and
- Living space for countless water-purifying organisms.
There are more than 25 types of underwater plants (i.e. submersed macrophytes) that can be used in NSPs. Do not scrimp on this plant group as they work against algae formation from the beginning.
Oxygenators, one of the most important pond plants of them all, are also often the most overlooked. Either free-floating or rooted, these essential plants not only provide much-needed air for a healthy pond, they also filter water, provide cover for fish and other pond life, act as a main food source for fish—directly and indirectly—and most importantly, they compete for the same nutrients as algae. Absorbing nutrients through their leaves and stems, oxygenators keep the water clean and clear, while algae blooms are eliminated. Any pond containing fish will not be a healthy pond unless it is well-stocked with oxygenators.
Because oxygenating plants acquire nutrients from their leaves and stems, they can often be planted in gravel. Those without roots do not need to be planted at all. Quite simply, these plants can be the easiest to maintain in a NSP. Here are some popular specimens:
Brazilian waterweed (Egeria densa)
Zones: Six to 11
Exposure: Part sun, part shade.
Planting depth: Grows fine as a free-floating aquatic oxygenator, but can also be planted 152 to 457 mm (6 to 18 in.) below water into soil or gravel/sand. Anacharis is great for aerating the water, as well as algae control and fish cover.
Canadian pondweed (Elodea Canadensis)
Zones: Three to 10.
Exposure: Full sun to part shade.
Planting depth: Grows fine as a free-floating aquatic oxygenator, but can also be planted 152 to 457 mm (6 to 18 in.) below water into soil or gravel/sand. Elodea is a great NSP oxygenator and is a well-used staple.
Hornwort
Zones: Four to 10.
Exposure: Part sun (direct sunlight may burn exposed tips).
Planting depth: A free-floating aquatic oxygenator, Hornwort is a complete aquatic plant with thinly branched, bristly leaves that fork out underwater.
Parrot feather (Myriophyllum aquaticum)
Zones: Six to 10.
Exposure: Full sun to part shade.
Planting depth: Parrot feathers are a submerged oxygenator that can be planted in soil or bare-rooted in water. Bright blue-green, feathery foliage sits upright at the water’s surface, sometimes up to 305 mm (12 in.) high. This plant is excellent for water filtration and aeration.
Sagittaria subulata
Zones: Eight to 11.
Exposure: Full sun to part shade.
Planting depth: These plants can be submerged up to 610 mm (24 in.) over the top of the pot. This sagittaria is a vigorous producer of showy, multi-headed white flowers with green-yellow centres. They can be planted pond side, in shallow water, or medium water depths.
