Myriophyllum rubricaule

Red-stemmed parrot's feather is an attractive species of water milfoil that is still little known as an aquarium plant but has long been used in outdoor water gardens. For many years, this stem plant was incorrectly sold as "Myriophyllum brasiliensis" before being described as a new species, Myriophyllum rubricaule, in 2022. It was initially known only from cultivation, but was later found to be native to Chile, ranging from the Valparaíso Region to the Los Ríos Region. Like M. aquaticum, M. rubricaule usually grows with floating shoots and produces blue-green, water-repellent emergent leaves. Unlike the former, its leaves are smaller and its stems are a deep dark red.
Underwater, the plant develops yellowish green, reddish to golden-brown leaves with very fine, thread-like leaf segments. These are somewhat reminiscent of Myriophyllum pinnatum, but the whorls of leaves are spaced much farther apart. The stems branch moderately. Once the shoots reach the water surface and continue growing as floating shoots, they produce emergent leaves again.

Myriophyllum rubricaule is a relatively undemanding and very fast-growing aquarium plant. Medium to strong lighting, soft to moderately hard water, and a complete nutrient supply through the water column are recommended. Thanks to its wide temperature tolerance of 4–28 °C (optimum 15–25 °C), it is suitable for both coldwater and tropical aquariums. CO₂ supplementation is not essential but significantly improves growth and colouration. Like other stem plants, it is easily propagated from stem cuttings and shoot tips. For the best effect, plant several stems together in a group. Because of its rapid growth, regular trimming is necessary. Cutting back and replanting the shoot tips encourages bushier growth and helps prevent the lower stems from becoming bare.

Myriophyllum rubricaule looks its best when grown as a group about 20–50 cm tall in the midground to background of larger aquariums. Its fine, soft texture adds depth and a sense of lightness to the layout while contrasting beautifully with plants that have broader leaves. The pale foliage also stands out strikingly against the dark red stems.
The emergent and floating growth forms are also attractive for aquascaping. In open aquariums and well-lit paludariums, the blue-green, feather-like leaves and dark red stems create eye-catching accents. Thanks to its broad temperature tolerance, Red-stem Water Milfoil is also an excellent choice for enclosures housing subtropical animals.