The Genus Hygrophila

(Unedited version)
Originally appeared in the June 2006 issue of
Tropical Fish Hobbyist Magazine

The genus Hygrophila contains several beautiful aquatic plants with some dramatically different submerged leaf growths that are easily grown in the aquarium.

Hygrophila are angiosperms in the family Acanthaceae. This family also includes over 200 genera and 2500 species of mostly tropical shrubs, herbs, vines and even a few trees. About 100 of those species are in the genus Hygrophila. Hygrophila means water loving and these plants do love moist areas, usually growing emersed along natural bodies of water or in swampy areas. Only a few of species of Hygrophila have found their way into the aquarium trade so far but new species and cultivars sometimes become available.

Hygrophila are stemmed plants and easily trimmed and replanted. Remember the nodes (the area where the leaf comes out) are where you're new roots and stems will grow from so be sure to leave several on each piece of plant you intend to grow. Since the Hygrophila have larger leaves it's best to not plant the stems in bundles, though you can certainly plant them as close together as their growth and your lighting will allow.

Hygrophila balsamica

H. balsamica is starting to get some attention in the United States. It's a lovely plant with a feathery leaf appearance that's native to India and Sri Lanka. H. balsamica is reported to be a somewhat more difficult species to maintain than the more common Hygrophila, needing CO2 and high lights to grow well. The emersed form of H. balsamica is also reported to release toxins in the water that can kill fish and invertebrates in your aquarium. However the submersed growth is apparently safe for aquarium inhabitants. Still I would be cautious with this plant.

Hygrophila corymbosa

H. corymbosa is the scientific name behind several different looking varieties that are often sold under different names. This is one of those areas where scientific names can get confusing because H. corymbosa is also called H. angustifolia, salicifolia, siamensis and stricta among others. And if that's not confusing enough the genus is also sometimes labeled as Nomaphila or even less commonly as Justicia.

How does this happen and what does it mean?

The genus Hygrophila was originally described by Robert Brown in 1810. Brown collected more than 3,000 plants in Australia, about 2/3rds of which were new species. Then in 1826 Carl Ludwig von Blume, who studied the flora of Southern Asia, described the plant Nomaphila corymbosa. In 1895 Gustav Lindau described the same plant as Hygrophila corymbosa. Because this plant was found to be in the genus Hygrophila, which was described first, the official name is Hygrophila corymbosa.

Name changes are not unusual in the world of science. Sometimes people will describe and name 2 different organisms that are later found to be in the same genus sometimes it's even the same species. But science likes things to be correct and when these problems are later discovered, the are corrected. In almost all instances the official name will be determined to be the first one given. If the plant is found to belong to another genus but is still a unique species then only the genus will be changed and the species name stays the same.

And where does the genus Justicia come from? This genus was described even earlier than Hygrophila or Nomaphila by Martin Vahl. Vahl was an early botanist that studied under Linnaeus. There are other plants still under this genus but they are different from Hygrophila.

Another issue that comes up is varieties. These can be man made or naturally occurring. If plants are labeled correctly these variety names occur after the genus and species. In the instance of H. corymbosa there are several varieties which are often mislabeled as the species name, some may have been at one time believed to be different species. Getting the right name can be pretty confusing but these lovely plants from Southeast Asia are wonderful in the aquarium.

Most of the H. corymbosa varieties grow tall, and have somewhat larger leaves. This makes them more practical as background or centerpiece plants. When purchasing H. corymbosa, regardless of which variety you get, they will probably have been grown emersed. Usually after planting in your aquarium some or all of the leaves grown this way will eventually die off and new growth will occur. Fortunately this plant is generally not difficult to grow even in moderate lighting, though you will have better results in higher light levels. With their large leaves and good growth you do have to be careful that lower leaves are getting light. It's not uncommon for these plants to loose lower leaves after the upper ones block their light.

H. corymbosa varieties include: “angustifolia” which has narrow leaves, “compact” which is a more recent bushy cultivar, “siamensis”which is an easy plant that likes to grow out of the tank and bloom, and “stricta” a large leaved variety often called giant hygro.

Hygrophila costata (lacustris)

H. costata is the only North American species of Hygrophila. It grows naturally from Southern North America through Central America and into South America.

H. costata, like H. corymbosa was described as several different plants and then those were all decided to belong to the same species determined to be H. costata. The plant was originally described by Christian Gottfried Daniel Nees von Esenbeck in 1824. Nees von Esenbeck was a German botanist who described over 7,000 different plants in his lifetime. Other names this plant was described under include the genus Ruellia and the species names, brasiliensis, conferta, guianensis, hispida, lacustris, longifolia, portoricensis, pubescens, rivularis, and verticillata.

Like H. corymbosa, H. costata is usually grown emersed before purchase. New growth in the aquarium can bring a different look to the leaves, usually lighter in color and a bit smaller, depending on the conditions in the the aquarium. It's an attractive plant and though it does grow a bit slowly it's not a difficult plant to grow in bright lighting.

Though a native to the Americas H. costata has been introduced elsewhere in the world where it has become an invasive weed. In Australia where it was introduced, it's called Glush Weed and has become a problem.

Hygrophila difformis

H. difformis is a beautiful plant from India, Burma, Thailand and the Malay Peninsula. It was first described by Linnaeus himself in 1781 as Ruellia difformis. It's also been called Ruellia triflora, Synnema triflorum and Hygrophila triflora. It's common name is Water Wisteria.

This is my personal favorite of the Hygrophila. It's a lovely plant with a very fern like appearance in the aquarium. When this plant is grown out of the water it has a much different looking leaf. The emersed leaves are darker and oval, giving no clue to the wonderful lacy leaves that form under water.

Water Wisteria is easy to grow in the aquarium. It tolerates moderate to high lighting. It's versatile and can be kept trimmed to mid height or allowed to grow tall in the background or center of the aquarium. Because of it's unusual appearance and bright green foliage, it's a distinctive plant in the aquarium. H. difformis is also sometimes available in a white and green bi-color cultivar.

Hygrophila polysperma

H. polysperma is also from India and was once a very common aquarium plant. H. polysperma made it's debut in North America around 1950 or perhaps a bit earlier. It was definitely listed in books published in 1952. It's a very easy to grow plant and a number of beautiful cultivars were developed. Unfortunately the ease of it's growth has become it's downfall.

H. polysperma was introduced in to Florida waters sometime in the 1950's. Since then it has become a big problem and is listed by the federal government as a noxious weed. There are different state and federal laws involved in noxious weeds. For a long time these laws were mostly ignored but in recent years there has been more of an effort to control these plants. You can still occasionally see them for sale but they shouldn't be. It's a sad story for a great aquarium plant and a lesson for us all to never, never release anything in to the wild.

Final Thoughts

The genus Hygrophila offers several beautiful plants for the aquarium hobby. Studying them can be an interesting course in the history of botany and some of the people who risked life and limb to discover new plant species in the infancy of the field. New hybrids and cultivars are still being developed and perhaps new species will come to the hobby in the future. These are wonderful stemmed plants for the aquarium, generally not difficult to grow and with enough leaf shapes to fit a wide range of decorating themes. If you haven't already I suggest you give a Hygrophila a place in your planted aquarium.

Questions or Comments?

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