North America Native Plant

Smooth Browntop

Botanical name: Microstegium glabratum

USDA symbol: MIGL13

Life cycle: annual

Habit: grass

Native status: Native to Pacific Basin excluding Hawaii  

Smooth Browntop: A Little-Known Pacific Island Native Grass Meet smooth browntop (Microstegium glabratum), one of the Pacific’s more mysterious native grasses. If you’ve never heard of this plant, you’re not alone – it’s a relatively obscure annual grass that calls some of our most remote Pacific islands home. While it ...

Smooth Browntop: A Little-Known Pacific Island Native Grass

Meet smooth browntop (Microstegium glabratum), one of the Pacific’s more mysterious native grasses. If you’ve never heard of this plant, you’re not alone – it’s a relatively obscure annual grass that calls some of our most remote Pacific islands home. While it might not be the showstopper of the plant world, smooth browntop has its own unique story worth telling.

What Exactly Is Smooth Browntop?

Smooth browntop is an annual graminoid, which is a fancy way of saying it’s a grass or grass-like plant that completes its entire life cycle in just one growing season. As part of the diverse world of grasses, sedges, and their relatives, this plant represents the incredible botanical diversity found across the Pacific Basin.

Where Does It Call Home?

This native grass has quite the exclusive address – it’s naturally found in Guam and Palau, making it a true Pacific Basin endemic. Its native range excludes Hawaii, so don’t expect to stumble across it during your next Big Island vacation. This limited distribution makes smooth browntop a special representative of the unique flora found on these remote Pacific islands.

Should You Grow Smooth Browntop?

Here’s where things get interesting – and a bit challenging. While smooth browntop is undoubtedly a legitimate native species deserving of respect, there’s remarkably little information available about growing it in cultivation. This isn’t necessarily a bad thing; it just means this grass has been living its life quietly in its native habitat without much fanfare from the gardening world.

For most gardeners, especially those outside of tropical Pacific regions, smooth browntop probably isn’t going to be your go-to grass choice. The lack of cultivation information, combined with its highly specific native range, suggests this is a plant that’s perfectly content in its natural Pacific island setting.

The Mystery of Growing Conditions

Unfortunately, specific growing requirements for smooth browntop remain largely undocumented in horticultural literature. Given its native habitat in Guam and Palau, we can make some educated guesses:

  • Likely prefers warm, tropical conditions year-round
  • Probably adapted to Pacific island soil conditions
  • May have specific moisture requirements tied to its island ecology
  • As an annual, would need to reseed each growing season

A Plant Worth Knowing About

Even if you never encounter smooth browntop in a garden center (which is highly unlikely), it’s worth appreciating as part of our planet’s incredible botanical diversity. This modest grass represents the specialized flora that has evolved in isolation on remote Pacific islands, adapting to very specific environmental conditions over countless generations.

For gardeners interested in native Pacific plants, you might want to explore other better-documented native grasses and plants from your specific region that offer similar ecological benefits with more available growing information.

The Bigger Picture

Smooth browntop serves as a reminder that not every native plant needs to become a garden darling to be valuable. Some plants are perfectly content doing their important ecological work in their native habitats, supporting local ecosystems in ways we’re only beginning to understand. Sometimes, the best thing we can do for these species is simply appreciate them from afar and support conservation efforts in their native ranges.

While smooth browntop might not be coming to a garden near you anytime soon, it’s a fascinating example of the specialized plant life that makes our world’s remote islands so botanically unique and worth protecting.

Smooth Browntop

Classification

Group

Monocot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Liliopsida - Monocotyledons

Subclass

Commelinidae

Order

Cyperales

Family

Poaceae Barnhart - Grass family

Genus

Microstegium Nees - browntop

Species

Microstegium glabratum (Brongn.) A. Camus - smooth browntop

Plant data source: USDA, NRCS 2025. The PLANTS Database. https://plants.usda.gov,. 2/25/2025. National Plant Data Team, Greensboro, NC USA