Proserpinaca palustris, which is commonly called Mermaid weed in the industry, can be found in nature in both North and South America. Though it has been in the hobby for a long time, the plant has never been very popular among hobbyists - perhaps due to its large size or difficulty in growing it to good form.
Proserpinaca palustris ranges from being greenish to orangey red. It is a stem plant that will grow as tall as large aquariums with a circumference of around 3 to 4 inches at full size. It has distinct serrated leaves that gives the plant leaves an attractive sawtooth look. It can be used as an attractive midground or background bush. Its large size when matured makes it more suitable for larger sized tanks. Its broad canopy means it will shade surrounding areas quite a bit.
Varietal differences account partly for why some plants have more finely divided leaves. Generally, well fed plants with access to high CO2 levels have fatter leaves.
Thankfully it is not a fast grower, it grows at moderate speed even though it will get large in time. Unlike many other stem plants, this plant does not form many lateral shoots as well as it grows. While it can be trimmed straight; discard top and allowing the bottom portion of the stem to sprout side shoots, it is usually neater to cut and replant the top, discarding the bottom. This plant will start looking very messy if repeated straight trims are done. Cutting and replanting the top and any side shoots that sprout will generally give a tidier bush.
Mermaid weeds prefers a tank with a lot of light. Higher PAR (100+ umols) couple with stronger red/blue spectrum is necessary to bring out its best colors. It also prefers a high level of CO2 and nutrient availability - lacking which the plant will become more thin and small. There is close correlation between CO2/nutrient availability and the overall size of the plant; which makes it a good indicator plant for those factors.
It can grow in low tech tanks with higher light levels, but the plant will be thin.
Cut off and replant the top, leaving the bottom rooted part to sprout new shoots. The plant will naturally sprout side shoots as it grows taller. These can be cut off and planted elsewhere.