Plant atlas

Geographical Origin and Habitat: A marsh species historically known to botanists and veteran South American aquarists, *Hedyotis salzmannii* (also known by the old synonyms *Oldenlandia salzmannii* or as "Dwarf Bacopa") is native to the coasts of South America, primarily southern Florida, eastern Brazil, Argentina, and Paraguay. In its natural biotope, it lives on flooded muddy coasts and along the moist grassy banks of streams and swamps, resisting very well both in the creeping emersed form and in the caulescent submerged one.

Taxonomy & Genetics: It belongs to the Rubiaceae family (the same biological family as the coffee plant, a rather peculiar case for an aquatic plant). Its appearance inevitably leads novices to confuse it with *Bacopa caroliniana* or *Bacopa monnieri*. Genetically, Hedyotis does not share the lemon-scented essential oil typical of Bacopa, nor its roughness, but boasts a much softer, more slender, and herbaceous structure.

Physical Structure: Erect caulescent architecture of small dimensions in submersion, and prostrate and creeping in emersion. The stems are pale, extremely thin, and delicate, branching copiously from every cut or bent node. The leaves, narrow, oval, and elliptical, no longer than 1 cm, are always arranged in opposite decussate pairs (crosswise). At the ends of the emerged stems, solitary and enchanting small white or pale pink flowers with four cross-shaped petals bloom.

Color & Texture: It maintains a sober uniform, a bright light green or apple green devoid of red hues. Its true aesthetic strong point is the texture and delicacy of its structure compared to *Bacopas*. While the leaf blades of *Bacopa* are rigid and fleshy, those of *Hedyotis salzmannii* are very soft, thin, fragile, and silky to the touch, swaying poetically and dynamically to the slightest current in the tank.

Lighting & CO2: An extremely frugal plant in its demands. Medium lighting (PAR 30-50) is more than sufficient to guarantee healthy and vertical growth, without causing the excessive etiolation typical of other stem plants. It can easily do without gaseous carbon dioxide fertilization, but will benefit from liquid carbon. If pushed with intense light and CO2, it compacts the internodes becoming a very florid bush, but will demand incessant pruning.

Nutrition & Substrate: It extracts its mineral nourishment in a balanced way both from the tiny and superficial capillary roots in the substrate, and by absorbing it from the leaf pores directly from the water (N, P, and K). Simple gravel enriched with root tabs and weekly column fertilization is perfect. It is not an extreme nutrient devourer like *Hygrophila*, guaranteeing stability to Low-Tech aquariums.

Water Chemistry: Relatively easygoing in terms of parameters. It likes classic tropical Amazonian water at 22-26°C with neutral or weakly acidic pH (6.0 - 7.0), but will also thrive in medium-high hardness typical of cut tap water (KH 5-8). The only conditions it dislikes are saline excesses or overly invasive algaecide/antibacterial treatments, which burn its tender stem.

Space Management & Placement: Thanks to its slender and low nature, *Hedyotis salzmannii* is a superb "transitional plant". Its masterful use in aquascaping is in the midground to elegantly mask the transition from the lawn to the wall of background stems. By planting dense groupings of cuttings about 10 cm high along the edges of the rocks, beautiful structured green "avenues" are formed (the classic dwarf 'Dutch Street').

Pruning: Its massive lateral branching makes pruning very rewarding. The classic topping operation (decapitation of the stem) is used, cutting with short-bladed scissors at mid-height. The old stem will fork rapidly, thickening the hedge, while the removed top can be replanted laterally. If used in Wabi-Kusa or paludariums, it will be left to creep, pruning the escaping edges.

Risks & Diseases: No significant chemical risk or metabolic collapse, provided normal fertilization with trace elements is maintained. Conversely, its thin and slender constitution makes it the perfect target for the voracity of phytophagous fish and for physical damage by large digging cichlids which, by rummaging or moving the sand near the roots, will easily uproot the bush, sending it adrift.