Pearlweed

Hemianthus glomeratus

Also known as Micranthemum glomeratum, Hemianthus micranthemoides, Micranthemum micranthemoides, Baby tears, Manatee mudflower

FreshwaterStemCuttingsSide shoots

Pearlweed (Hemianthus glomeratus) — Aquarium Plants Factory · Used with permission

Care at a glance

Light: Medium light
CO2: CO₂ beneficial
Temperature: 68–82°F; 20–28°C
Max height: 7.9 in; 20 cm

Growth rate: Fast
Placement: Midground
Type: Stem
pH: 5.0–7.5
Hardness: 2–15 dGH
Spread: 3.9 in (10 cm)
Nutrient uptake: Root + water column
Growth region: Submersed or emersed
Difficulty: Beginner
Family: Linderniaceae
Origin: Florida, USA (endemic)

Overview

Pearlweed is a small-leaved, fast-growing stem plant for the midground. It is one of the easiest stem plants going and suits beginners.

Did you know

Pearlweed was sold as Hemianthus micranthemoides for decades, until it was identified as Micranthemum glomeratum in 2011. The real Hemianthus micranthemoides was last collected in 1941 and is presumed extinct.

Caring for pearlweed

Strip the lower leaves and push pearlweed stems into the substrate a little apart. It is happy in a low-tech tank without CO2, though injected CO2 makes it denser and more compact. Give it medium light and keep it at 68 to 82°F (20 to 28°C).

It feeds through its roots and its leaves, so root tabs and a liquid fertilizer both help. It grows fast, and in a fast tank it needs pruning every week. Replant the tops and side shoots, or let it spread on its own.

Left tall, pearlweed grows into a bright green midground bush or a bushy background stem. Trimmed hard and kept in high light, it creeps sideways and hugs the substrate as a loose carpet. That lets one plant fill three different roles, depending only on how often you trim it.

Good to know

Pearlweed's accepted botanical name is Micranthemum glomeratum, and Hemianthus glomeratus is a synonym widely used in the aquarium trade. Hobbyists use the names Hemianthus glomeratus and Hemianthus micranthemoides almost interchangeably. It is placed in the family Linderniaceae, though some sources still list it under Plantaginaceae.

In the wild

Pearlweed is an amphibious plant endemic to Florida. It grows on wet sandy mud along the margins of lakes and slow streams. It creeps over damp ground when emersed and grows as a loose submersed stem when flooded. Botanists know it as the manatee mudflower.

Common questions

Does pearlweed need to be planted in the substrate?

Yes. Strip the leaves from the lower part of each stem, then push the stems into the substrate one at a time, a little apart.

Does pearlweed need CO2?

No, but it helps. Pearlweed can grow without injected CO2, and added CO2 makes it grow faster.

How much light does pearlweed need?

Pearlweed wants medium light. A light sold for planted tanks covers it.

Does pearlweed need root tabs?

They help. Pearlweed takes nutrients through both its roots and its leaves. Root tabs near its roots and a liquid fertilizer cover both.

How do you propagate pearlweed?

Pearlweed propagates by cuttings and side shoots. Cut off the top of a stem and replant it, and the stump left behind grows new shoots. Cut a side shoot off once it has a few leaves and plant it on its own.