blue waterhyssop

Crushed leaves of Bacopa caroliniana give off a lemon scent, which is one of the plant's most distinctive traits. It comes from the southern and central United States and Mexico, where it grows in marshes both under water and above it, and it has been kept in aquariums for many years.

The ovate leaves wrap their bases all the way around the stem. Flowgrow lists heights of 20 to 60 cm, while Tropica describes stems of 10 to 30 cm that branch readily from the base. Several forms are in cultivation, among them a smaller-leaved one and a variegated one that looks much like the standard plant.

The two sources read its needs a little differently. Tropica calls it undemanding and slow enough to need little attention, which makes it a good first stem plant. Flowgrow's entry says it wants a lot of light, at least 0.5 watts per litre, and that fertiliser and CO₂ make only a small difference. Its optimum is 20 to 25 °C at pH 5 to 7.5. Strong light combined with little nitrate turns the leaves bronze or brownish, and a shortage of phosphate gives them a slight pink tint.

Take cuttings from the tips or side shoots, or cut off the runners that form at the base of the stems and replant them. A stepped group in the midground, or in the foreground of a larger tank, gives neighbouring plants something to build around. In a temperate summer it can also be grown emersed at the edge of a pond, where it grows fast with a creeping habit, hairy stems and purple flowers.