Monte Carlo (Micranthemum 'Monte Carlo'): grower data and history

What the grower data says

Tropica rates ‘Monte Carlo’ medium on difficulty, light and CO2, with medium growth and a height of 3–5 cm ^[1]. Aquasabi’s profile matches on difficulty, light and growth, lists CO2 as required and gives a lower care height of 1–3 cm ^[3]. Tropica’s description is precise about the conditions: the plant can grow in light shade, but needs good light and added CO2 to develop optimally and become really compact ^[1].

Its place in the trade comes from a comparison. Tropica received its first sample in January 2013 and grew it in its laboratory beside Hemianthus callitrichoides ‘Cuba’, Micranthemum umbrosum and Glossostigma elatinoides. It grew much like HC ‘Cuba’ but proved more adaptable and easier, growing faster and making a full carpet even at lower light and CO2 ^[2]. That is the reason it sits in Tropica’s medium category while HC ‘Cuba’ sits in advanced.

Placement and planting

Aquasabi classes it as a foreground ground cover ^[3]. Tropica’s article describes preparing a pot by removing the mineral wool, dividing the plant into several portions with a little wool left on each, and inserting them into the substrate with tweezers ^[2]. A nutrient-rich substrate such as an aqua soil “will help its growth considerably” ^[2].

The same article describes a second use: given enough nutrition in the water, ‘Monte Carlo’ can grow as an epiphyte wedged into gaps in rock or wood, or fixed with a small amount of glue, where it grows in a cascading form ^[2].

Growth and trimming

It spreads by runners and forms a solid carpet ^[2]. Once established it is a fast grower that needs frequent, hard trimming. If the carpet gets too thick, Tropica warns, it tends to lift up and float as the lower layers die from suffocation and lack of light ^[2]. Floating trimmings should be netted out and disposed of responsibly. Tropica also advises regular liquid fertilizing with enough light, CO2 and circulation ^[2].

Names and taxonomy

The plant was first sold under its trade name. Tropica’s article says that in 2017 Christel Kasselmann identified it botanically as Micranthemum tweediei ^[2]. The World Checklist of Vascular Plants, however, treats Micranthemum tweediei Benth. as a synonym of Micranthemum umbrosum (J.F.Gmel.) S.F.Blake, in the family Linderniaceae ^[4]. So the checklist places ‘Monte Carlo’ in the same species as the M. umbrosum that Tropica trialed it against, even though the aquarium forms behave differently.

WCVP’s native range for M. umbrosum is broad: the south-eastern United States, Mexico, Central America, the Caribbean and much of South America, including north-east and north-west Argentina ^{[4, 5]}. That is consistent with Tropica’s statement that ‘Monte Carlo’ originates from Argentina ^[1].