North America Native Plant

Monte Torrecilla Thoroughwort

Botanical name: Koanophyllon droserolepis

USDA symbol: KODR2

Life cycle: perennial

Habit: subshrub

Native status: Native to Puerto Rico  

Synonyms: Eupatorium droserolepis B.L. Rob. (EUDR)   

Monte Torrecilla Thoroughwort: A Rare Puerto Rican Native Worth Protecting If you’re passionate about native plants and conservation, you may have heard whispers about the Monte Torrecilla thoroughwort (Koanophyllon droserolepis). This fascinating shrub represents one of Puerto Rico’s botanical treasures – and unfortunately, one of its most endangered plants. What ...

Rare plant alert!

Region: Conservation status by state

Status: S1: Status is uncertain but is somewhere between the following rankings: Critically Imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 5 or fewer occurrences or very few remaining individuals (<1,000) ⚘

Monte Torrecilla Thoroughwort: A Rare Puerto Rican Native Worth Protecting

If you’re passionate about native plants and conservation, you may have heard whispers about the Monte Torrecilla thoroughwort (Koanophyllon droserolepis). This fascinating shrub represents one of Puerto Rico’s botanical treasures – and unfortunately, one of its most endangered plants.

What Makes This Plant Special?

The Monte Torrecilla thoroughwort is a perennial shrub that’s completely native to Puerto Rico. Like other shrubs, it’s a multi-stemmed woody plant that typically grows less than 13-16 feet tall, with several stems arising from near the ground. You might also see it listed under its former scientific name, Eupatorium droserolepis, in older botanical references.

Where Does It Grow?

This rare beauty calls Puerto Rico home – and nowhere else in the world. Its geographic distribution is limited to this Caribbean island, making it what botanists call an endemic species.

The Conservation Reality: Why This Plant Needs Our Help

Here’s the sobering truth: Monte Torrecilla thoroughwort has a Global Conservation Status of S1, which means it’s critically imperiled. This classification indicates there are typically only 5 or fewer known locations where this plant exists, with fewer than 1,000 individual plants remaining in the wild.

This extreme rarity makes the plant especially vulnerable to extinction, whether from habitat loss, climate change, or other environmental pressures.

Should You Grow Monte Torrecilla Thoroughwort?

If you’re lucky enough to live in Puerto Rico or a similar tropical climate (USDA hardiness zones 10-11), you might be wondering if you should add this plant to your garden. Here’s what you need to know:

  • Only source responsibly: Due to its critically endangered status, never collect this plant from the wild
  • Work with conservation groups: If you’re interested in growing this species, connect with botanical gardens or conservation organizations in Puerto Rico
  • Consider it a conservation effort: Growing this plant isn’t just about landscaping – you’d be participating in species preservation

Growing Conditions and Care

While specific growing requirements for Monte Torrecilla thoroughwort aren’t well-documented (another consequence of its rarity), we can make educated assumptions based on its native Puerto Rican habitat:

  • Climate: Tropical to subtropical conditions
  • Hardiness: Likely suited for USDA zones 10-11
  • Role in landscape: Best suited for specialized native plant gardens or conservation collections
  • Garden type: Conservation-focused landscapes or educational botanical displays

The Bigger Picture

Monte Torrecilla thoroughwort represents more than just another plant species – it’s a reminder of the incredible biodiversity we’re at risk of losing. While we don’t have complete information about its pollinator relationships or specific wildlife benefits, every endemic species plays a unique role in its ecosystem.

If you’re passionate about native plants but can’t access this rare species, consider supporting conservation efforts in Puerto Rico or growing other native Puerto Rican plants that are more readily available and less threatened.

Final Thoughts

Monte Torrecilla thoroughwort stands as both an opportunity and a responsibility. For the few gardeners who might have the chance to grow it, remember that you’re not just adding a plant to your collection – you’re becoming a guardian of a species teetering on the edge of extinction. Always source plants through legitimate conservation channels, and consider your garden a small but vital ark for Puerto Rico’s irreplaceable botanical heritage.

Monte Torrecilla Thoroughwort

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Asteridae

Order

Asterales

Family

Asteraceae Bercht. & J. Presl - Aster family

Genus

Koanophyllon Arruda - thoroughwort

Species

Koanophyllon droserolepis (B.L. Rob.) R.M. King & H. Rob. - Monte Torrecilla thoroughwort

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