Polygonella myriophylla (Small's jointweed)

Plate 1 figs. a–h · 8 separate observations

Polygonella myriophylla, photographed by novvictan — fig. a novvictan, CC BY 4.0 / 2021-03-14 / obs. 116491707

Polygonella myriophylla, photographed by Jay Horn — fig. b Jay Horn, CC BY 4.0 / obs. 40075593

Polygonella myriophylla, photographed by Daniel Estabrooks — fig. c Daniel Estabrooks, CC0 1.0 / obs. 21554990

Polygonella myriophylla, photographed by Brandon Corder — fig. d Brandon Corder, CC BY 4.0 / obs. 174564513

Polygonella myriophylla, photographed by Ryan McMinds — fig. e Ryan McMinds, CC BY 4.0 / obs. 138313906

Polygonella myriophylla, photographed by Scott Ward — fig. f Scott Ward, CC BY 4.0 / obs. 111363009

Polygonella myriophylla, photographed by Valerie Anderson — fig. h Valerie Anderson, CC BY 4.0 / obs. 47890947

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

Flowering 130 in flower of 190 examined

32%

76%

83%

88%

87%

97%

100%

83%

40%

17%

Proportion of examined Polygonella myriophylla in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	4	too few examined
Feb	0	10	0%	0% to 28%
Mar	10	31	32%	19% to 50%
Apr	16	21	76%	55% to 89%
May	25	30	83%	66% to 93%
Jun	14	16	88%	64% to 97%
Jul	13	15	87%	62% to 96%
Aug	28	29	97%	83% to 99%
Sep	11	11	100%	74% to 100%
Oct	10	12	83%	55% to 95%
Nov	2	5	40%	12% to 77%
Dec	1	6	17%	3% to 56%

Peak flowering in Sep. Each bar is the share of Polygonella myriophylla observations in which someone actually recorded the reproductive state and found the plant in flower, not the raw number of flowering records. That distinction matters: people observe plants far more in spring than in winter, so a bare count of flowering records partly measures when people go outside. Dividing by the number examined removes that. 130 of 190 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. One month has fewer than 5 examined observations, so no proportion is drawn for it. This is still a global aggregate and not a forecast for your garden: the same species flowers on different dates in different hemispheres. Where a species has fewer than 30 flowering records we do not draw this chart at all. Computed from 10.15468/dl.cgje2x.

Where it actually grows measured, from 541 observations

Condition	5th percentile	Median	95th percentile
Coldest month, mean daily low	11.4 °C	11.9 °C	12.4 °C
Warmest month, mean daily high	31.7 °C	31.9 °C	32.0 °C
Annual rainfall	1,302 mm	1,330 mm	1,364 mm
Rainfall in the driest quarter	145 mm	157 mm	171 mm

It is not found anywhere that gets close to freezing. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 541 research-grade observations of Polygonella myriophylla that carry a coordinate, and this is the range those places actually span. The 5th and 95th percentiles are used rather than the minimum and maximum, because a single cultivated specimen in a heated conservatory should not widen a tropical plant's range to the Arctic.

This is not a hardiness zone. A USDA zone is the average annual extreme minimum temperature. The figure above is the mean daily minimum of the coldest month, which is a different quantity and is typically far warmer. Reading one as the other would place a plant several zones too warm, so we do not publish a hardiness zone, because we do not have one. Climate from CHELSA V2.1 (Karger et al. 2017); occurrences from 10.15468/dl.cgje2x.

Sourcesevery claim on this page

World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. Retrieved 2026-07-13.

We publish what we can source and we say so when we cannot. This page has no care advice and no toxicity claim, because we do not yet have those from a source we can cite. It has no native range either: Kew's checklist does not cover this taxon.