The Planted Tank: Swordplants: Not Just for Amazonian Fish Tanks

Author: Amanda Wenger

With summer in full gear, I figured I’d talk about one of my favorite genera for indoor and outdoor aquaria alike: swordplants (genus Echinodorus). With a wide variety of species, cultivars, and hybrids to choose from, there’s a swordplant for almost any application save for nano aquaria (for small tanks, turn to the related but much smaller genera Helanthium and Ranalisma).

SWORDPLANTS IN THE WILD

Echinodorus are indigenous to the Americas, with more species found in South America than its northern counterpart. Two US natives, E. berteroi (commonly known as the cellophane sword) and E. cordifolius (best known for its variegated cultivar “marble queen”) are prominent in the hobby, whereas the South American E. grisebachii species complex (Amazon swordplants) were some of the first aquarium plants. This is the plant that immediately comes to most hobbyists’ minds when they hear the word “swordplant.” Other prominent species include E. uruguayensis (often sold as E. osiris, the melon sword)

In their native habitats, swordplants grow in the margins and shores of lakes, rivers, and ditches. While seasonal flooding may place them temporarily underwater, they generally are partly or entirely out of water for at least some portion of the year. Nonetheless, they are suitable for indefinite submersed culture.

WILD REPRODUCTION

Echinodorus means “horned skin,” a reference to the spiny, beaked fruits of the plant (which have also earned the genus common name “burhead”). While production of these fruits is necessary to produce the myriad hybrids found in the aquarium trade, swordplants rely a great deal on vegetative reproduction to spread.

Crowns of large mother plants will divide, and they also produce plantlets at the nodes of the long inflorescences (called scapes). When the scape is loaded with large plantlets, it bends over sideways, allowing the plantlets to root a foot or two (30 to 61 cm) away from the mother plant. Successive generations of inflorescences allow the plant to “walk” around the edges of the water, and any scapes broken off by wading birds or other animals can drift off and potentially root elsewhere.

SWORDPLANTS IN THE AQUARIUM

Broadly speaking, swordplants are for big tanks. The smallest cultivars, such as the “Tropica” sword (usually sold as E. parviflorus, though it’s really part of the E. grisebachii complex), reach some 6 inches (15 cm) in height, a comfortable size for a midground in a medium tank or a foreground in a very large setup. Larger species will exceed 18 inches (46 cm) in ideal conditions—both vertically and horizontally. The rosette structure of a swordplant makes it ideal for a centerpiece specimen, as the lanceolate leaves naturally draw the eye inward to the center of the plant.

Swordplants need only moderate lighting to survive and even thrive, but they look most spectacular when allowed to flourish in a brightly-lit, CO2-injected setup. In these conditions, swordplants will reproduce prolifically and grow massive enough to shade and outcompete many smaller plants (which leads to their infrequent use in formal aquascaping), but they have some use in larger Dutch-style aquascapes (a single plant functions as a hedge in its own right).

Swordplants in the aquarium hobby are a bit like roses in terrestrial gardening. (With a little imagination and a lot of disregard for the fine details of botany, their flowers even look a little bit like those of a wild rose.) What I mean by this is that they have been repeatedly hybridized and selected for various attributes to the point that no one can really keep track of every single kind available.

Every year, various nurseries across the globe release new versions with varying characteristics—interestingly patterned foliage, different shapes and sizes of leaves, color variants, and so forth. This means that hobbyists have a lot of variety to choose from, and even if one kind of swordplant doesn’t thrive for you (personally, I’ve never had a lot of luck with melon swords for some inexplicable reason), others may.

Swordplants are heavy root feeders, so a rich substrate and/or the use of root tabs are ideal. They are particularly iron-needy, so keep an eye on micronutrient levels. Once they settle in, swordplants form massive, invasive root structures, so be certain in your placement of a specimen because attempting to relocate it later on can easily lead to uprooting half your tank (or worse).

Beyond the nutrient needs, however, swordplants are generally unfussy and are often recommended as beginner plants because they’re reasonably adaptable. New hobbyists are often disheartened, however, when their newly purchased swordplant drops all of its leaves and looks dead a few weeks after they place it in their tank. Don’t be too alarmed if this happens to you—most swordplants are cultivated in emersed form by nurseries, and the stiff, brittle leaves you purchase them with are not conducive to a submersed lifestyle.

In response to suddenly finding themselves underwater, emersed-grown swordplants will shed their emergent-form leaves and grow new, softer leaves suitable to aquatic life. Acclimation may take several weeks up to a few months, but don’t write your swordplant off as a failure too quickly. If the crown turns to mush, then it’s dead. Otherwise, give it some time to bounce back.

SWORDPLANTS OUTDOORS

One of the most overlooked uses for swordplants, in my opinion, is their potential as pond and water garden plants. As generally tropical and subtropical species, any swordplant will thrive in the open summer sun and heat, and mine go crazy in my greenhouse, throwing scapes all over with pretty, one-inch (2.5-cm) white flowers.

One of my personal favorites is an Echinodorus x “Altlandsberg” mother plant I’ve had for several years now. In emersed culture, this particular hybrid displays dark green leaves with deep burgundy markings along the major veins. It’s particularly floriferous, and by the end of each summer, it’s produced dozens of baby swordplants for me to take to local clubs for the fall show and auction season.

Swordplants will thrive placed as a marginal plant in pots along the edges of ponds. They make an excellent choice for summer tubs, where the crown can provide shelter for young fish and the above-water growth eats up nitrates in the water and provides shade cover. Their foliage is even attractive enough to make a nice table centerpiece for outdoor dining—try placing a potted swordplant in a decorative bowl of water to keep its feet wet.

CONSERVATION ALERTS

In particularly warm climates, such as the Gulf states in the United States, swordplants can be kept outdoors year-round. In these states, where some Echinodorus are also native, be very careful to introduce nonnatives and hybrids only into closed, ornamental ponds; escapees could outcompete the native species and upset the natural ecosystem. This is especially true in the area of Pensacola, Florida, where an isolated population of E. grandiflorus is found—the only such population on this continent. E. grandiflorus is otherwise a South American species, so upon its discovery, the Florida population was briefly described as a new species (E. floridanus) until further study placed it within its currently recognized species.

This is, incidentally, the largest American swordplant species (and one of the largest Echinodorus species), with leaves that can reach 4 feet (120 cm) from base to tip and scapes of a similar length. Its size makes it a bit impractical for use in indoor aquaria, but it can be attractive along the edge of a pond.

SWORDPLANTS EVERYWHERE

I hope I’ve given you a few more options to consider when growing Echinodorus species. We’ve come a long way from just having Amazon swordplants under incandescent lights, and as the genus is a hobby mainstay, I look forward to seeing what future efforts in breeding and hybridization will bring us—and to what other alternative uses swordplants may be put.