North America Native Plant

Leafy Horseweed

Botanical name: Laennecia sophiifolia

USDA symbol: LASO2

Life cycle: annual

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Conyza coulteri A. Gray var. tenuisecta (COCOT)  âš˜  Conyza sophiifolia Kunth (COSO2)  âš˜  Eschenbachia tenuisecta (A. Gray) Wooton & Standl. (ESTE)   

Leafy Horseweed: A Lesser-Known Native Worth Knowing If you’re on the hunt for truly native plants that most gardeners have never heard of, let me introduce you to leafy horseweed (Laennecia sophiifolia). This humble annual forb might not win any beauty contests, but it’s got something special going for it ...

Leafy Horseweed: A Lesser-Known Native Worth Knowing

If you’re on the hunt for truly native plants that most gardeners have never heard of, let me introduce you to leafy horseweed (Laennecia sophiifolia). This humble annual forb might not win any beauty contests, but it’s got something special going for it – it’s a genuine native of the American Southwest that’s been quietly doing its thing long before any of us started gardening.

What Exactly Is Leafy Horseweed?

Leafy horseweed is an annual forb, which is just a fancy way of saying it’s a soft-stemmed plant (not woody) that completes its entire life cycle in one year. Like many plants in the vast sunflower family (Asteraceae), it’s not going to stop traffic with its looks, but it plays an important role in its native ecosystem.

You might also see this plant listed under its scientific synonyms in older references, including Conyza sophiifolia or Conyza coulteri var. tenuisecta. Botanical names have a way of evolving as scientists learn more about plant relationships!

Where Does It Call Home?

This southwestern native has a pretty specific address – you’ll find it naturally occurring in Arizona, New Mexico, and Texas. It’s perfectly adapted to the unique growing conditions of the American Southwest, having evolved alongside the region’s other native plants and wildlife.

Should You Plant Leafy Horseweed?

Here’s where I need to be completely honest with you – leafy horseweed isn’t exactly what you’d call a showstopper in the garden design world. This is more of a plant for the hardcore native plant enthusiast or someone creating a truly wild, naturalized area. If you’re looking for something with serious curb appeal, you might want to consider other southwestern natives that pack more visual punch.

However, if you’re passionate about supporting local ecosystems and growing plants that are genuinely native to your specific region (and you live in the Southwest), leafy horseweed could be an interesting addition to a native plant collection or naturalized area.

Growing Conditions and Care

Since this plant is native to the southwestern United States, it’s naturally adapted to:

  • Hot, dry conditions
  • Well-draining soils
  • Full sun exposure
  • Minimal water once established

As an annual, leafy horseweed will complete its entire life cycle in one growing season. This means you’ll need to allow it to set seed if you want it to return the following year, or you’ll need to replant.

Based on its native range, this plant is likely hardy in USDA zones 7-10, though specific hardiness information is limited.

The Reality Check

Let’s be real – information about growing leafy horseweed in cultivation is pretty scarce. This isn’t a plant you’ll find at your local nursery, and there aren’t extensive cultivation guides available. If you’re determined to grow it, you’ll likely need to source seeds from native plant societies or specialized native seed companies.

For most gardeners interested in southwestern natives, you might have better luck with more commonly available options like desert marigold, penstemon species, or native grasses that offer similar ecological benefits with more reliable growing information.

Wildlife and Ecological Value

While specific wildlife benefits of leafy horseweed aren’t well-documented, plants in the Asteraceae family typically provide nectar and pollen for various small pollinators and insects. The seeds may also provide food for birds and small mammals, contributing to the local food web.

The Bottom Line

Leafy horseweed is one of those plants that’s more interesting from an ecological and botanical perspective than a horticultural one. If you’re a native plant purist working on habitat restoration or creating a comprehensive collection of regional natives, it might be worth seeking out. For most home gardeners, however, there are probably more practical and beautiful native options that will give you better bang for your buck.

Sometimes the most valuable plants aren’t the prettiest ones – they’re the ones that remind us of the incredible diversity of native flora that exists right in our own backyards, even if we rarely notice them.

Leafy Horseweed

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

Laennecia Cass. - horseweed

Species

Laennecia sophiifolia (Kunth) G.L. Nesom - leafy horseweed

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