Disk Waterhyssop Bacopa rotundifolia
Disk Waterhyssop is a perennial wildflower native to Canada and the lower 48 states. It grows to 0.1 ft and blooms Oct in part shade – shade.
More about this plant
Bacopa rotundifolia is a species of water hyssop known as the disk water hyssop or round-leafed water hyssop, due to the shape of its leaves. This is an aquatic plant native to water bodies of the central United States and well known in other areas as an invasive weed of waterways. The round leaves are 1 to 3 centimeters wide and each has six longitudinal veins. The plant produces yellow-throated white flowers. The plant is in bloom during the fall, its fruit/seed abundance is medium and its seed spread rate is slow. The plant has no commercial use. Wikipedia →
Growing & care
USDA PLANTS · TRY- Sun
- Part shade – shade
- Soil & moisture
- High moisture
- Soil pH
- 5.4–7.8
- Fertility need
- Low
- Adapts to
- Medium (loam), Fine (clay)
- Hardiness
- USDA zone 4+
- Height
- 0.1 ft
- Spacing
- 2–4 ft apart from USDA planting density
- Spread
- Moderate
- Growth rate
- Slow
- Growth form
- Stoloniferous
- Lifespan
- Perennial · moderate
- Foliage
- Broadleaf · medium texture
- Active growth
- Spring through autumn
- Flower colour
- Green AI AI image-analysis of community-science photos — lower-confidence (a more subjective call, often an inconspicuous flower); not a botanical record
- Propagate by
- Seed, Bare root, Container
- Seed starting
- No stratification needed
- Seeds ripen
- Autumn seed-collection / harvest window
- In the trade
- No known commercial source
- Resprouts if cut
- No
Sow timing keys off your local last- and first-frost dates.
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~1 caterpillar species
Bacopa supports ~1 caterpillar species.
Native butterfly & moth caterpillars are the base of the terrestrial food web — most songbirds rear their young almost entirely on them. As a host for native Lepidoptera this is a modest genus.
Recorded feeding on Bacopa in North America, including:
Wildlife & visitors 1 nectaring
Open records of who else uses Disk Waterhyssop — a generalist food-web signal, kept separate from the keystone Ecological Value.
1 adult butterfly & moth species is recorded nectaring at its flowers:
Related plants
More Bacopa →
How we know this (3) Methods & honest limits
We read each species’ measured specific leaf area (leaf area per unit dry weight) from the Global Spectrum dataset and band it: thin & fast (high SLA), medium, or thick & tough (low SLA). The global median is about 10 mm²/mg.
Honest limits: A species-mean from pooled measurements — individual plants vary with light and site. A broad strategy signal, not a precise per-plant figure.
We take the plant’s U.S. county range and look up each county’s long-term climate, then summarise: native rainfall = the median annual rainfall across its counties; heat tolerance = the warm end (90th percentile) of average temperature across its range (mirroring how our cold-hardiness floor uses an extreme). Counties + medians blunt the roadside/observer bias that makes point-level climate unreliable. Needs at least five placeable counties.
Honest limits: A realized, sampling-biased niche (where it has been recorded, not its physiological optimum), and county climate is coarse — large Western counties span deserts and mountains. Derived guide, never a measured fact.
McKenzie et al. assigned each species a flower colour with a GPT-4V vision model over iNaturalist photos. We use the confident tier plus a separately-labelled lower-confidence top-up (mostly inconspicuous green/brown flowers), and render it as a small tint — never as an asserted fact, and kept out of the written synopsis.
Honest limits: AI image inference (~87% expert agreement on the confident tier); a decorative, confidence-tiered indicator, not a measured trait.
Sources for this entry (32) Open & cited
Cite this page Open data, please attribute
PlantKey’s data is open under CC BY-SA 4.0 — free to reuse and adapt, with attribution and the same licence. Photos keep their own per-image licence + credit (see Sources above).
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