Lady’s Thumb, Redshank, Heart’s Ease, Heartweed, Spotted Knotweed
Persicaria maculosa Gray is the correct and accepted scientific name for the Lady’s Thumb. It was named and described by Samuel Frederick Gray in Natural Arrangement of British Plants in 1821. Persicaria maculosa var. amblyophylla is currently the only accepted variety of P. maculosa listed by Plants of the World Online and are native of Japan.
Plants of the World Online by Kew lists 68 synonyms of Persicaria maculosa which you can view by clicking HERE. I didn’t want to list them all…
The genus, Persicaria Mill., was named and described by Philip Miller in the fourth edition of Gardener’s Dictionary in 1754.
Plants of the World Online by Kew lists 128 species in the Persicaria genus (as of 5-19-21 when this page was last updated). It is a member of the plant family Polygonaceae with 55 genera. Those numbers could change as updates are made by POWO. The number of species in the genus goes up and down by a few quite often.
The above distribution map is from Plants of the World Online. Areas in green are where they are native and purple is where they have been introduced. The map on the USDA Plants Database for the United States and Canada is the same. The USDA still lists the species as Polygonum persicaria (which is a synonym of Persicaria maculosa).
The map on iNaturalist shows where members have made observations. Anyone can join and it is a great website to confirm and share your observations.
THERE ARE A FEW LINKS AT THE BOTTOM OF THE PAGE FOR FURTHER READING AND TO HELP WITH A BETTER POSITIVE ID.
Out of seven species of Persicaria on the farm, there are fewer P. maculosa than any. When I started photographing the Persicaria species to make proper identification in 2019, I noticed their numbers had dropped to just a small colony in front of the Mulberry trees in the front pasture. I had taken photos since 2013 that are labeled Persicaria maculosa, but I didn’t know as much about their characteristics then so they may have been P. longiseta instead (they rank #2 in population).
Racemes of flowers are normally around 1 1/2″ long (more or less) sometimes with small “auxiliary” racemes at the upper leaf nodes and even possibly lower nodes as well. Their small flowers include 5-6 sepals and usually six stamens, and no petals. Flower color is usually shades of pink but can be reddish, greenish-white, or purple even on the same raceme. Flowers are shy, so if you see a few open you are lucky. Persicaria maculosa flowers do not have cilia (hairs) like P. longiseta, nor do they have “punctate glandular dots” like P. hydropiper and P. punctata. So, if you see hair on the raceme or glandular dots on the flowers, you do not have P. maculosa.
While typically shorter, their leaves can grow up to 6″ long x 1″ wide. Persicaria maculosa are decumbent, which means their stems typically sprawl on the ground and turn upward. So, their stems are usually longer than they appear. As with most Smartweeds, they are multi-branching.
The translucent ocrea (sometimes spelled ochrea) around the leaf node can have a few bristles but may fall off with age. Here you can see a few branches starting to emerge. Stems are usually a dark reddish-green and more reddish at the nodes.
The alternate leaves are up to 6″ long and 1″ across, although usually smaller. They are lanceolate or linear-lanceolate, hairless, smooth along the margins, and sometimes slightly ciliate. Each leaf has a short petiole or it is nearly sessile (no petiole). The leaves are kind of dark green with lighter areas and MAY have a dark spot as in the third photo above.
Hmmm… I pulled this stem to show how long they can get, but looking back I don’t think I should have done that. At the time I didn’t realize this small colony in front of the Mullberry trees was the only area they were growing… The Persicaria in the background is a mixture of Persicaria longiseta and Persicaria punctata.
The above photo is a good example of longer and shorter leaves on the same plant. This is kind of common with Persicaria species (and most plants in general). You can also notice the color of the leaves and stems pretty well in this photo.
There are a few key features to help you identify Persicaria maculosa. 1) their racemes are kind of “blunt” on top rather than looking more pointed (especially from a distance”. 2) Flowers of different colors on the same raceme (shades of pink, red, greenish-white, purplish). 3) NO glandular dots on the flowers. 4) No cilia on the flowers. 5) Sometimes the ocrea around the leaf nodes on the stems have bristles (cilia) but not necessarily. 6) Dark leaves UP TO 6″ long but usually shorter, with sometimes a dark spot in the center of the leaf. But not always. In short, typically a pink-flowered plant with kind of blunt inflorescences. Flowers have no hair and some of the leaves may have a dark spot resembling a thumbprint.
Persicaria species are very interesting once you realize their uniqueness. Most species flowers rarely open and appear to always be buds. However, they are not only self-pollinating, but they can also pollinate without opening. Most flowers pollinate after they open.
Persicaria maculosa seeds are small, black, and shiny. You may be thinking, “duh!” But not all Persicaria seeds are black and shiny BUT Persicaria longiseta seeds are dull and can be blackor brown.
On September 22 when I took the above photo, it appears the flowers of the Persicaria maculosa are beginning to dry. One weird thing about Persicaria species is that even long before the flowers dry they already have seed. One seed per flower.
I enjoyed the experience identifying the seven species of Persicaria growing on the farm. You can read the post about them all by clicking HERE where you will also find links to their own pages.
I have enjoyed photographing and learning about the many wildflowers growing on the farm and other areas. I have grown over 500 different plants and most have pages listed on the right side of the blog. I am not an expert, botanist, or horticulturalist. I just like growing, photographing and writing about my experience. I rely on several websites for ID and a horticulturalist I contact if I cannot figure them out. Wildflowers can be somewhat variable from location to location, so sometimes it gets a bit confusing. If you see I have made an error, please let me know so I can correct what I have written.
I hope you found this page useful and be sure to check the links below for more information. They were written by experts and provide much more information. If you can, I would appreciate it if you would click on the “Like” below and leave a comment. It helps us bloggers stay motivated. You can also send an email to me at email@example.com. I would enjoy hearing from you.
FOR FURTHER READING:
PLANTS OF THE WORLD ONLINE (GENUS/SPECIES)
INTERNATIONAL PLANT NAMES INDEX (GENUS/SPECIES)
FLORA OF NORTH AMERICA (GENUS/SPECIES)
WORLD FLORA ONLINE (GENUS/SPECIES)
USDA PLANTS DATABASE
KANSAS WILDFLOWERS AND GRASSES
NOTE: The data (figures, maps, accepted names, etc.) may not match on these websites. It depends on when and how they make updates and when their sources make updates (and if they update their sources or even read what they say). Some websites have hundreds and even many thousands of species to keep up with. Accepted scientific names change periodically and it can be hard to keep with as well. Some of the links may use a name that is a synonym on other sites. In my opinion, Plants of the World Online by Kew is the most reliable and up-to-date plant database and they make updates on a regular basis. I make updates “at least” once a year and when I write new pages or add new photos but I do get behind. We are all a work in progress. 🙂