North America Native Plant

Roadside Crabgrass

Botanical name: Digitaria similis

USDA symbol: DISI2

Life cycle: perennial

Habit: grass

Native status: Native to Puerto Rico  

Synonyms: Trichachne affinis Swallen (TRAF)   

Roadside Crabgrass: A Lesser-Known Puerto Rican Native Grass If you’re exploring native plants of Puerto Rico, you might come across roadside crabgrass (Digitaria similis), a perennial grass that’s as humble as its name suggests. While it may not win any beauty contests in the plant world, this unassuming grass plays ...

Roadside Crabgrass: A Lesser-Known Puerto Rican Native Grass

If you’re exploring native plants of Puerto Rico, you might come across roadside crabgrass (Digitaria similis), a perennial grass that’s as humble as its name suggests. While it may not win any beauty contests in the plant world, this unassuming grass plays its part in Puerto Rico’s natural ecosystems.

What is Roadside Crabgrass?

Roadside crabgrass belongs to the large Digitaria genus, which includes many species commonly known as crabgrasses. Don’t let the crabgrass name scare you off completely – unlike some of its weedy cousins that gardeners battle in their lawns, Digitaria similis is a native perennial grass that belongs in Puerto Rico’s landscape.

This grass species was previously classified under the scientific name Trichachne affinis, so you might encounter it under that name in older botanical references.

Where Does It Grow?

As its name suggests, Digitaria similis is native to Puerto Rico, where it has adapted to local growing conditions over thousands of years. True to its roadside moniker, you’ll typically find this grass growing along roadsides and in disturbed areas throughout the island.

Should You Plant Roadside Crabgrass?

Here’s the honest truth: unless you’re working on a specialized native plant restoration project in Puerto Rico or have a particular interest in native grasses, roadside crabgrass probably isn’t the plant for your garden wishlist. Here’s why:

  • It offers limited ornamental value compared to showier native plants
  • Information about cultivation requirements is scarce
  • It’s primarily valued for ecological restoration rather than landscaping
  • Seeds and plants are not readily available in the horticultural trade

Growing Conditions and Care

If you are interested in growing roadside crabgrass, here’s what we can piece together about its needs:

  • Climate: Tropical to subtropical conditions (likely USDA zones 10-11)
  • Habitat: Adapted to disturbed soils and roadside conditions
  • Maintenance: As a native species, it should require minimal care once established in appropriate conditions

Unfortunately, detailed growing guides for this species are virtually non-existent, reflecting its limited use in cultivation.

Wildlife and Ecological Value

Like many native grasses, roadside crabgrass likely provides some ecological benefits in its native range, potentially offering habitat and food sources for local wildlife. However, specific information about its wildlife relationships isn’t well-documented.

Better Native Alternatives for Puerto Rico

If you’re gardening in Puerto Rico and want to include native plants in your landscape, consider these alternatives that offer more ornamental appeal:

  • Native flowering plants that support pollinators
  • Indigenous shrubs and trees with attractive foliage or flowers
  • Native ferns and other plants suited to your specific garden conditions

The Bottom Line

Roadside crabgrass represents the quieter side of native plant conservation – not every native species needs to be a garden star. While Digitaria similis may not earn a spot in most home landscapes, it serves as a reminder that biodiversity includes both the showy and the understated. For most gardeners, appreciating this species from afar while choosing more ornamental native plants for cultivation is the practical approach.

If you’re specifically working on habitat restoration or have a particular research interest in Puerto Rican grasses, roadside crabgrass might have a place in your projects. Otherwise, there are plenty of other beautiful native plants waiting to transform your Puerto Rican garden into something spectacular.

Roadside Crabgrass

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

Digitaria Haller - crabgrass

Species

Digitaria similis Beetle ex Gould - roadside crabgrass

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