The Alismaceae (Al-is-MAH-kay-ee) family of plants is a varied collection of plants found in streams, ponds, and flooded places all around the globe. Many people are interested in these plants because of their relevance to their local ecologies and the use of select species by hobbyists.
From the smallest Sagittaria filiformis, with its thin, short leaves and tiny white flowers, to the type genus Alisma, with its fleshy green leaves and sprays of small white or pink flowers, to the largest Sagittaria and Echinodorus species, there is a wide enough range of leaf form and growth habits to keep taxonomists busy and hobbyists interested for a long time.
In fact, the whole family’s name is clearly in doubt. The majority of publications refer to it as Alismataceae, although a minority refer to it as Alismaceae.
One has to wonder where the additional -ta- comes from. Regardless, the family has 11 genera, at least four of which are found natively in the United States. Alisma, Damasonium, Echinodorus, and Sagittaria are the species. Caldesia, Wisneria, Burnatia, Luronium, Limnophyton, Ranalisma, and Baldellia are the other genera.
The majority of these are from Africa and Europe and are represented by a single, or at most, three or four species. The diverse distribution of the plants in the group suggests that the family has been around for a very long period, and was most likely present on Pangea, a long-gone supercontinent.
“If these plants are so different in shape and behaviour, what makes them so similar that they may be classified in the same family?” While the leaves are unique, the essential architecture of the plants is similar, and similarities may be detected in comparisons of how the plants develop and reproduce.
Root
The first resemblance is in the root. All of these plants grow on rhizomes that may range from delicate, herbaceous stems to strong, fibrous masses of semi-woody tissue.
Some rhizomes produce offspring every few weeks, meaning that the plantlets are close together on the horizontally growing rhizome, producing a clump of plants that fan out from the starting point (Sagittaria lancifolia), while others produce a plantlet only once every few months (Echinodorus spp.), producing less dense clumps.
Most rhizomes grow horizontally, but others grow vertically, with offspring clustering around the parent plant (Sagittaria montevidensis). Others generate runners, resulting in new plants every few to several inches. In shallow or deep water, these plants ultimately develop thickets on sandy or muddy soils.
Leaves
The leaves emerge in a rosette arrangement from the rhizome and may be on petioles (stems) ranging in length from very short to two feet or more. The petioles are encased at their bases, which may be seen as the little wing-like structures that emerge from the interior of the leaf stem’s base and travel up the stem a few inches. Immature leaves are usually filiform (hairlike), subulate (bladelike), or ovate, and mature only when two or more leaves have been created.
Leaves are frequently noticeably veined, with the veins being extremely apparent at times. There are virtually always leaf shapes for each circumstance in those plants that grow submerged or emersed. Submergent foliage is often softer and denser than emerged foliage, which may be somewhat rough. Species that create diverse leaf shapes in response to environmental changes do so quickly.
When the floods arrive, emergent Echinodorus plants instantly transition to submerged leaf forms, and when the water recedes during the dry season, they react by growing tougher emergent foliage and blooms.
Flowers
Flowers, which are the primary indications of differentiation, are always carried on a generally branching but sometimes unbranched stem and are grouped in whorls of 3 to 12 or 15 at intervals up the stem, culminating in a cluster of flowers at the summit.
Each flower has three petals that may vary in size from a few millimetres (“scale-like” to characterise some of them) to more than an inch wide. Blooms are normally white, however, some species include pink or purple flowers. Flowers with yellow centres are common, while S. montevidensis has a big red mark at the base of each petal.
Plants may be monoecious, with flowers of both sexes on the same plant, or dioecious, with blooms of both sexes on different plants. When they are monoecious, the female flowers are always borne underneath the male blooms, enabling wind-blown pollen to fall upon the female flowers when bees are not present. Flowers may be bisexual (Sagittaria) or unisexual (Sagittaria) (Echinodorus, Alisma).
Seeds
Runner production (Sagittaria subulata, Echinodorus tenellus), rootstock division (Alisma, etc.), seed production, and adventitious daughter plant formation at inflorescence nodes are all modes of reproduction.
Most of these plants’ seed production rates imply that they are essential food sources for many animal species. The Alismaceae as a group are unlikely to be too reliant on a single reproductive method. Seeds may be eaten or washed away; runners are successful, but plant thickets are vulnerable to grazing.
That fleshy rhizome has to be appetising to someone, particularly resting in the muck, plump and succulent in the dead of winter. Many Sagittaria species yield winter storage bulbs, which have traditionally been used by humans and animals. “Duck Potato” is one of their common names.
The seeds are in the shape of an acene, or achene, which is a dry, indehiscent seed capsule containing just one seed. The seeds are distributed in a radial, edge-on pattern around a central core.
The resultant seed cluster may be flattened or almost spherical, with a few dozen to several hundred seeds. The surface of the cluster is seldom smooth, with the roughness ranging from moderately grainy to practically spikey, giving rise to the popular name “Burhead” for one species, Echinodorus.
As the seeds mature, they fall off the old blossom and either float away to new grounds on water, or land in the mud and hope to be driven into the mud before being eaten.
In many situations, they germinate very quickly, allowing them time to establish themselves before winter hibernation or flooding. Similarly, we’ve seen seeds of S. montevidensis and several Echinodorus and Alisma species emerge after months or years of hibernation.
Many of these species reside in places that are not constantly covered in water and may even dry up entirely, therefore their seeds must be able to withstand prolonged periods of dryness.
Genera
Following is a study of each of the genera, with special emphasis on the two most significant genera, Sagittaria and Echinodorus.
Alisma
Depending on the source, the type genus, Alisma, is represented by at least three species and a handful of sub-species. The most frequent is A. plantago-aquatica, sometimes known as “Water Plantain.” Some taxonomists consider A. triviale and A. subcordatum to be subspecies of A. plantago-aquatica, while others consider them to be different species.
A. lanceolatum, often known as “Narrow Leaf Water Plantain,” is native to Europe and was just recently brought to the American market. It is very certainly doomed to become a weed in many places of this continent. Except in the far north and at the greatest altitudes, endemic North American species may be found almost wherever.
All Alisma species produce a rosette of lanceolate to ovate leaves on stems that are typically two or three times the length of the leaf blade from a central rootstock. If the circumstances are favourable, the leaves may develop to be very enormous. A. plantago-aquatica is 4″ long and 2.5″ broad in size.
Flowers are usually produced on tall, branching stalks that climb far higher than the leaves. As is characteristic of the family, the blooms are white (A. plantago-aquatica) or pink (A. lanceolatum).
Seeds are little, flat, disk-like acenes that are placed in a circle around the flower’s centre.
The majority of Alisma species reside in shallow water around pond borders that may or may not dry out. A. geyeri is a species that dwells in deeper water. All Alisma species may become invasive due to seed production, thus they must be thinned and/or stopped from generating seed on a regular basis.
Wisneria
Wisneria is made up of three species, all of which are found only in tropical Africa and Madagascar. These plants are constantly submerged or have partially floating linear to oblanceolate leaves that may reach a length of one metre.
Because of the narrowness of the leaf, it might be difficult to discern between the leaf blade and its stem.
The little blossoms rise just a few inches above the water and are kept extremely close to the stalk. Male blooms are higher on the inflorescence than female flowers, as is common across the family.
Young plants are sometimes produced by the lower whorls. W. filifolia is from Madagascar, W. triandra is from tropical Africa, and W. schweinfurthii is likewise from tropical Africa. This group of plants seems to be suitable for aquariums, but they are not currently accessible in the hobby, as far as I am aware.
Caldesia
Caldesia is the next genus. Caldesia consists of four species that are distributed in a vast geographical range that stretches from Europe to India and China, then down through tropical Africa and on to Australia. It should come as no surprise that some of them are now threatened by habitat degradation.
C. parnassifolium from Europe; C. reniformis from tropical Africa, India, and Australia; C. oligococca from India, Ceylon, and Australia; and C. grandis from India and China are the four species.
These plants are either submerged or create floating leaves, and they only emerge from the water to blossom. The leaves are elliptic to ovate in shape, having pointy or rounded apexes. Leaf bases are either truncated or chordate.
Luronium
L. natans is the only species in the genus Luronium. It is a creeping, low-growing shrub with short, elliptical leaves and 1″ white blooms. Flowers appear in clusters of one to five and emerge from the same nodes as the leaves. These same nodes generate roots. Seed heads are generally hemispherical and contain a large number of seeds. This genus is endemic to Europe and has spread into the United Kingdom.
Ranalisma
The following genus, Ranalisma, has two species: R. humile and R. rostratum. These are readily mistaken with Echinodorus, and various writers have given them that name throughout the years. R. humile is a weed found in West African rice fields.
The Malay Peninsula and Indochina are home to R. rostratum. They are low-growing plants with linear to ovate leaves that are upright or spreading. Flowers are borne individually or in clusters of up to three on a short stem. Flowers are bisexual, white, and tiny. Ranalisma species thrive in shallow water and seasonal dry places.
Limnophyton
Limnophyton is made up of three species: L. obtusifolium, which grows in tropical Africa, Madagascar, India, Ceylon, and the Malay Peninsula; L. angolense, which grows in tropical Africa (Angola); and L. fluitans, which grows in tropical West Africa as well.
All of these plants may be found in swamps, irrigation ditches, and ponds with still or slowly moving water. They have tall leaves with lengthy petioles. The apex of the leaves is rounded or blunted, while the bases are wedge-shaped or sagittate.
Blooms are held above the leaves on a stalk that branches twice or three times at the base and then produces 4 to 7 whorls of flowers. The little white blooms are arranged with male flowers on top and female and bisexual flowers on the bottom.
Baldellia
There is just one true species in the genus Baldellia, B. ranunculoides. Another species, B. alpestris, is sometimes identified; it is native to Europe and North Africa. Baldellia is also known as “Siberian Bog Pink,” and it is marketed under that name.
Baldellia looks similar to Echinodorus and is occasionally confused with it. The leaves are narrowly lanceolate and carried on slender stalks that may grow to be rather long. The leaves seldom surpass 2″ in length, but when the plants are crowded, the petiole might be 6 or more inches long.
Flowers are housed individually on little stems that radiate from the tip of a bigger stalk. The flowers are pink in the morning and fade to almost white by late afternoon.
Seeds are tiny (2mm) and beaked, ribbed, and ovoid, as is characteristic of the family. Because of its tendency of generating runners, this plant thrives in shallow water along streams and pools, establishing colonies.
Burnatia
Burnatia, which has just one species, thrives in tropical Africa’s sluggish streams, pools, and swamps. It has tall, erect stems with narrowly lanceolate to ovate leaves. These plants may grow to be very enormous, with petioles up to 16″ long and leaves up to 6″ long, and they can grow submerged or above water.
Because it is a dioecious species, the blooms are kept on separate plants. Male flowers have extremely little (1 mm petals) but are really bigger than female blooms, which have almost no petals. This would certainly make an excellent aquarium plant as well, but it is currently unavailable to us.
Echinodorus
With over 50 species, the genus Echinodorus is one of the biggest in the family. It has one of the best collections of aquarium and bog plants in the world. Members of this genus will stand out in the plant displays of both aquarists and outdoor water gardeners. Some species are suitable for both.
Echinodorus tenellus is the smallest Echinodorus and performs best in aquarium foregrounds. In that they generate runners, E. tenellus and E. quadricostatus develop similarly to Sagittaria subulata.
They are just around 6″ tall, with narrowly lanceolate leaves on long petioles. With its huge, attractive, widely lanceolate leaves on short petioles, the so-called “Amazon Sword Plant,” E. amazonicus, or E. bleheri, both make excellent centrepiece plants for aquaria.
These, like the rest of the species, produce inflorescences, but the blooms are smaller and the plant quickly produces adventitious progeny, as seen in many other species. These are species that live in lowland tropical climates rather than higher latitudes or altitudes, and so do not do well in colder environments.
Pond and bog plant farmers may choose from a variety of strong, floriferous plants that will thrive in a big or small pond or bog environment. Some of the same people who operate in aquaria also work in ponds, typically developing into eye-catching specimen plants in one to two feet of water (in the absence of goldfish or koi). E. osiris (“Melon Sword”), E. rosaefolia, E. horemannii (“Jade Sword”), E. ‘Red Rubin’, and E. uruguayensis are among them.
Many of them are cold hardy and may live for years without any extra care. E. uruguayensis has brilliant red, lanceolate leaves that float on the water in the spring.
Flowers quickly follow, and it is especially lovely when many of them are in full bloom. However, the springtime flush of youth fades as the plants begin to produce brown seeds and immature plantlets. With its big, rich red leaves, E. “Red Rubin,” E. rosaefolia, and E. osiris look lovely in a pond.
The leaves of the genus might be lanceolate, ovate, or chordate, brilliant green or dark crimson, or variegated with red or cream. One species, E. berteroi, is endemic to this location and has transparent green submerged leaves. As a result, it is sometimes known as the “Cellophane Sword.” Many species generate different kinds of leaves depending on their developmental stage or environmental circumstances.
Blooms are often carried above the water on long, branching stalks that produce several three-petaled, white or, in rare cases, purple flowers clustered at intervals along the blooming stem. Petals may range in size from a few millimetres to a full inch. Flowers are always bisexual.
The seeds are many and clustered around a central core, producing a tiny seed ball at the end of a short stem. The prickly surface formed by their gathered ends protruding out from the centre lends the group its common name, “Burhead.”
In the axils between the individual flower stalks and the main stem, adventitious daughter plants grow as well. This happens in high humidity or when the stem comes into contact with water. When these plants develop roots or root buds and are easily separated from the parent plant, they may be removed. The majority of Echinodorus species are relatively simple to cultivate.
Damasonium
Damasonium, one of four genera found in North America, is represented here by just one species, D. californicum, despite the fact that the genus has five additional species. D. californicum is exclusively found in northern California, is difficult to locate, and is potentially difficult to cultivate in southern California.
The remainder comes from Europe, North Africa, the Orient, Iran, and South Australia. They’ve clearly made their way around. Damasonium alisma (“Starflower”) grows in shallow water from the United Kingdom across Europe and south to North Africa, producing floating lanceolate leaves and little white flowers raised just above the water.
D. minus (“Starfruit”) is a weed found in Canadian rice fields. D. bourgaei is a European species that develop in places that dry out on a regular basis. It has tiny chordate leaves and tiny white or pink blooms.
Sagittaria
Sagittaria is the biggest and most diversified genus. As previously stated, this genus includes species as different in shape as the grass-like S. filiformis and the massive S. montevidensis. As with Echinodorus, plants in this genus are suited for aquariums, ponds, or both.
S. subulata and its dwarf sister, S. subulata subulata, are the most common in aquariums, with S. filiformis being too difficult to get in the commercial market to be utilised for anything. Depending on the kind, they all form thickets of varied heights.
Although seeds are formed and germinate, runners are the most common method of reproduction. They are utilised in the aquarium as a lawn in front of the tank or as a screen across the rear. They produce a lovely white-flowered lawn in shallow water or as under-plantings for water lilies in the pond. They work well as oxygenators.
The sky is the limit in the bog. With its huge sagittate leaves and red-spotted blooms, S. montevidensis is an excellent accent plant for a pond edge or a specimen plant in a barrel planting. S. lancifolia, sometimes known as “Bulltongue,” may blend in with taller plants in the backdrop of a picture. It may compete with Cyperus papyrus, tall Irises, and other huge, aggressive plants. It has enormous blooms that are characteristic of the genus.
There are at least three varieties of this plant: one with green stems, one with red stems, and one with red variegations near the base of the stem. It has relatively thin leaves, while the green and red types have large leaves. S. graminea is beneficial in low bogs along the pond’s edge or in front of it. It, like many other emergent species, colonises a vast region with its runners, including S. sagittifolia and S. latifolia.
One interesting feature worth noting here is that when Sagittaria grow from seeds, they display all of the genus’ leaf shapes up to and including their own mature form. In other words, they all begin with filiform leaves. The first group, consisting of three subulate forms, never develops beyond the subulate form, which comes after filiform. S. subulata, the biggest of the subulate species, sometimes develops tiny, spotted, oval leaves at or near the water’s surface.
The next group comes to an end with ovate or lanceolate leaves. S. lancifolia, S. graminea and all of its variants, and others are included in this category. The sagittate (arrowhead-shaped) leafed species are the final group to progress through all of the preceding leaf forms and conclude with sagittate leaves of varying sizes and shapes. There are thin ones, wide ones, long and short ones, little and huge ones, but all are sagittate. Sagittifolia, montevidensis, latifolia, and many additional species are included in this group.
Sagittaria reproduction methods include the formation of runners, which places the progeny at a distance from the parent plant (S. subulata, S. graminea, S. latifolia).
For their dormancy, these plants often generate subterranean storage tubers. Many animals and indigenous peoples use these as food. A Sagittaria may potentially split at the rootstock (S. lancifolia, S. montevidensis). The root of S. lancifolia is a rhizome that forks at irregular intervals as it develops horizontally over the ground. The root of S. montevidensis grows vertically, with the children crowded around the parent.
Almost often, the parent plant dies in the winter, leaving a circle of daughter plants to take over the site in the spring. Finally, there is a seed production, which may be significant in certain species.
Over the course of a season, a well-cared-for S. montevidensis specimen might easily generate several thousand seeds. All three reproduction techniques are represented in all leaf shape categories.
The species that generate runners are less ideal for use as a potted plant than the “clumpers” since they crowd their pots. These species are better adapted to more open environments, such as native bog planting.
In San Diego, all Sagittaria species may flourish. Because many of them are from extremely frigid winter places, nothing that southern California has to offer them poses a danger. Some species, like S. montevidensis, do not necessarily winter tolerant, therefore harvest seeds in the summer and autumn to germinate in the spring.
The maintenance requirements differ depending on the kind of plant. Subulate species must be trimmed on a regular basis or they will choke out other plants as well as each other. As with any other plant, all emergent species must be maintained clear of dead leaves. Those that produce runners need to be thinned if they are in a restrictive area. It is never a bad idea to repot specimens each spring.
Without a doubt, Alismataceae is an important family of plants with two particularly important genera, Echinodorus and Sagittaria, within it. These plants are useful not only as efficient oxygenators but also as decorative additions to our aquatic gardens, both underwater and above it. I can usually find space for at least two or three species in my pond and aquarium plantings.