AQUATIC HORTICULTURE		BY KAREN RANDALL

KAREN RANDALL

Aquatic Plant Overview Continued —
The “B” Genera

There are approximately 100 species of Bacopa. Most are aquatic and found in warm regions of the world, primarily the Americas. When you consider that only two of these species are offered for aquarium use with any regularity it becomes apparent that this genus may well provide other interesting plants for aquarists as time goes on. Actually, I suspect there may be more than two species currently in the hobby, as there seems to be quite a bit of variation among the plants that are seen. Whether these represent different species or are just variations within a species remains the work of taxonomists!

The first of the two species commonly offered commercially is B. monnieri. Grown submersed, this species has small, rounded light-green leaves that are evenly spaced along a slender upright stem. It needs to be planted in a group to make much of a statement, but at the same time, must be given enough room so the light can get to it. Otherwise, it will lose leaves on the lower stems and become spindly. It branches readily on the surface of the water and this habit can be used to advantage if you want to increase your supply. The stems tend to be somewhat brittle, so handle it with care.

If allowed to lie on the surface or, better yet, to crawl up out of the tank, it becomes a low lying creeper, with shiny, fleshy leaves. It flowers readily up close under the lights, producing many dainty pinkish-white flowers. In warmer areas, it can be left outdoors in ponds year round, and even in northern climates it grows fast enough to be a good plant for summer ponds. Just bring a few stems in before the frost and overwinter them in your aquarium!

Bacopa monnieri tolerates water that is quite hard, as long as it receives at least moderate amounts of light, and CO₂ is in adequate supply. In the wild, it is often found in brackish water, making it a good plant to try in a brackish aquarium.

The second species frequently offered in the trade is Bacopa caroliniana. As its name suggests, it is native to our eastern seaboard. Common names for the plant are Carolina water-hyssop and lemon bacopa. This second name refers to the lemony scent given off if the leaves are crushed. The leaves are larger than those of B. monnieri, darker in color and translucent when grown submersed. Under strong light, the top leaves often acquire a bronze tinge. This species will also flower if allowed to reach the surface of the tank, and, in this case, the flowers are a pretty pale blue.

This is a plant aquarists either love or hate. It can be very decorative when placed in a group at the back of a tall tank. But if conditions are not to its liking, it will quickly disintegrate into a pile of mush. If it is happy with the conditions provided, it grows with the speed of a weed and needs constant and vigorous trimming to keep it from crowding less-aggressive neighbors.

It is happiest under moderate to high light. And, in fairly soft water, B caroliniana will tolerate more hardness if supplemental CO₂ is supplied.

Barclaya
Family: Nymphaeaceae

There are three species in this genus, all native to Southeast Asia — B. longifolia, B. motleyi and B. rotundifolia. Of these, only B. longifolia is regularly offered for sale, although it has been reported that the other species do well in aquarium culture, as well.

Although Barclaya belongs to the water lily family, it is unusual in that it produces only submersed foliage, with no floating leaves. In the wild, it is sometimes found in relatively deep water. The leaves are long and narrow with wavy margins, prominent veins and a distinct petiole. The color of the leaves is variable, but the most common varieties are green on top with a pinkish bottom or bronze/red on top with a deep pink bottom.

Barclaya is one of the few plants that will not only flower readily under water, but is also capable of setting seed under these conditions. It can also be propagated by separating the offsets that may develop at the base of the plant.

B. longifolia requires moderate to high light levels. At the lower end of its lighting tolerance, the leaves will be shorter, broader and sometimes darker in color. It is not particularly fussy about water hardness, but does better if supplemental CO₂ is supplied in harder water. This is a plant that seems to prefer warmer water, so it is an ideal candidate for the planted discus tank. In my experience, it seems to do better with at least a small amount of organic material in the substrate.

Blyxa
Family: Hydrocharitaceae

There are nine known species in the genus Blyxa, all of which grow fully submersed, but bear emergent flowers. Unfortunately, many are annual plants native to temporary bodies of water. All are native to tropical areas of the old world, although there are naturalized populations in the U.S., as well. In the aquarium, these tend to be extremely demanding plants, but they are offered for sale occasionally, and they are decorative enough I thought they were worth including here.

B. aubertii is a rosette plant with sharply pointed narrow lanceolate leaves. The leaves are a beautiful bright cellophane green with a soft texture. While it can grow up to 30 inches in the wild, it seldom exceeds about 16 inches in the aquarium. To achieve even this, it needs bright light, soft water and an ample supply of CO₂. Under very bright light, the tips of the leaves sometime take on a reddish cast. B. aubertii is unlikely to reproduce sexually under aquarium conditions, but can produce offsets along its rhizome. These can be removed and planted elsewhere in the tank.

Blyxa japonica is the other species in the genus that has been offered for aquarium use in recent years. Like the previous species, it is a demanding aquarium subject. You are most likely to succeed with it if you have soft water, good strong light and supplemental CO₂. If you do succeed however, you will find this plant worth the effort. Unlike B. aubertii, the leaves are not confined to a rosette, but grow upward along a slender stem. The leaves are a dark bright green.