North America Native Plant

Water Smartweed

Botanical name: Polygonum amphibium var. stipulaceum

USDA symbol: POAMS

Life cycle: perennial

Habit: forb

Native status: Native to Alaska âš˜ Native to Canada âš˜ Native to the lower 48 states âš˜ Native to St. Pierre and Miquelon  

Synonyms: Persicaria amphibia (L.) Gray var. stipulacea (N. Coleman) H. Hara (PEAMS)  âš˜  Persicaria mesochora Greene (PEME10)  âš˜  Persicaria nebraskensis Greene (PENE10)  âš˜  Polygonum amphibium L. var. hartwrightii (A. Gray) Bissell (POAMH)  âš˜  Polygonum amphibium L. ssp. laevimarginatum Hultén (POAML)  âš˜  Polygonum coccineum Muhl. ex Willd. var. rigidulum (Sheldon) Stanford (POCOR2)  âš˜  Polygonum fluitans Eaton (POFL12)  âš˜  Polygonum hartwrightii A. Gray (POHA13)  âš˜  Polygonum inundatum Raf. (POIN14)  âš˜  Polygonum natans Eaton (PONA3)   

Water Smartweed: A Native Wetland Wonder for Your Garden If you’re looking for a native plant that thrives in wet conditions and brings both beauty and ecological benefits to your landscape, water smartweed (Polygonum amphibium var. stipulaceum) might just be your new best friend. This adaptable perennial has been quietly ...

Water Smartweed: A Native Wetland Wonder for Your Garden

If you’re looking for a native plant that thrives in wet conditions and brings both beauty and ecological benefits to your landscape, water smartweed (Polygonum amphibium var. stipulaceum) might just be your new best friend. This adaptable perennial has been quietly doing its thing across North America for centuries, and it’s about time more gardeners discovered its charms.

What Is Water Smartweed?

Water smartweed is a native perennial forb – basically a non-woody herbaceous plant that comes back year after year. Don’t let the weed in its name fool you; this plant is far from being a garden troublemaker. It’s actually a hardworking native that deserves a spot in the right garden setting.

You might also encounter this plant under several scientific aliases, including Persicaria amphibia var. stipulacea and Polygonum hartwrightii, among others. But regardless of what botanists call it, water smartweed remains the same reliable, water-loving plant.

Where Water Smartweed Calls Home

This plant is a true North American native with an impressive range. You’ll find water smartweed naturally occurring from Alaska all the way down through Canada and across most of the lower 48 states. It’s native to everywhere from Arizona and California to Maine and Florida, plus it grows in Canadian provinces from British Columbia to Newfoundland.

Why Your Garden (and Local Wildlife) Will Love It

Water smartweed brings several compelling benefits to the landscape:

  • Pollinator magnet: The pink to rose-colored flower spikes attract bees, butterflies, and other beneficial insects
  • Low maintenance: Once established, this tough native requires minimal care
  • Erosion control: Perfect for stabilizing pond margins and wet slopes
  • Wildlife support: Seeds provide food for waterfowl and other birds
  • Adaptable nature: Can grow in both aquatic and terrestrial conditions

Perfect Garden Settings

Water smartweed isn’t meant for your typical perennial border – it’s a specialist that shines in specific conditions:

  • Rain gardens and bioswales
  • Pond margins and stream banks
  • Wetland restoration projects
  • Naturalistic landscapes with wet areas
  • Areas with seasonal flooding

Growing Conditions and Care

The beauty of water smartweed lies in its adaptability and low-maintenance nature. Here’s what this plant prefers:

  • Light: Full sun to partial shade
  • Soil: Wet to moist conditions; can handle standing water
  • Hardiness: Thrives in USDA zones 3-9
  • Water: Loves consistently moist to wet soil

Planting and Care Tips

Getting water smartweed established is refreshingly straightforward:

  • Plant in spring after the last frost
  • Choose locations with reliable moisture or standing water
  • Space plants according to your desired coverage – they’ll naturally spread in suitable conditions
  • Minimal fertilization needed – this native is adapted to natural soil conditions
  • Allow plants to go to seed if you want to support wildlife

Is Water Smartweed Right for Your Garden?

Water smartweed is perfect if you have wet areas in your landscape that you’d like to turn into an asset rather than a problem. It’s especially valuable for gardeners interested in supporting native wildlife and creating sustainable, low-maintenance landscapes.

However, this plant isn’t suitable for traditional dry garden beds or formal landscapes. It needs consistent moisture to thrive and works best in naturalistic settings where its spreading habit is welcome rather than problematic.

If you’re working on a wetland garden, rain garden, or simply have a perpetually soggy spot in your yard, water smartweed could be the native solution you’ve been looking for. It’s a plant that proves sometimes the best garden additions are the ones that have been quietly thriving in our landscapes all along.

Water Smartweed

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Caryophyllidae

Order

Polygonales

Family

Polygonaceae Juss. - Buckwheat family

Genus

Polygonum L. - knotweed

Species

Polygonum amphibium L. - water knotweed

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