Easily confused with : Dame's-Violet but Honesty never has lilac coloured flowers as does Dame's-Violet. Honesty also has heart-shaped (cordate) leaves on the upper stem (but more rounded to ovate lower down the stem) that are also well-toothed whereas Dame's-Violet has lanceolate un-toothed leaves. Honesty has flat coin-shaped seed pods that turn silvery when ripe, whereas Dame's-Violet has long thin cylindrical seed pods typical of mustards.
Distinguishing Feature : the flat and papery-thin seed pods which are shiny and silvery in Summer.
Some similarities to: Perennial Honesty (Lunaria rediviva) from Europe escapes from gardens but that has ice-blue flowers and long, narrow elliptical fruits. This grows year in year out by means of underground runners, something which Honesty lacks. Perennial Honesty also has very elongated flat seed pods rather than the almost disc shaped of Honesty. Despite the binomial name of Honesty incorporating 'annua' Honesty is usually a biennial, or only occasionally annual but rarely perennially. Honesty is species which is most commonly grown in gardens and which is the more likely to escape, rather than Perennial Honesty.
The flowers are four-petalled and, on separate plants, are either purple or white, never lilac. They are a favourite cottage-garden wild flower. You are much more likely to find this plant either in a garden itself, or nearby houses than growing in the wild.
The rounded thin coin-shaped seed pods, when ripe in summer, turn from green to shiny silver. These are used as decoration in indoor dry-flower arrangements.
BENZO-FURAN SPERMIDINE ALKALOIDS
Lunarine is an alkaloid based upon a benzofuran (the three fused lower rings) and Spermidine. The Spermidine forms part of a large 20-membered ring straddling part of the benzofuran. Note that Spermidine is not symmetrical, but has four carbon atoms one side of the 'central' nitrogen atom, and only three on the other side of it. Which brings us to Lunaridine, where the molecule of Spermidine is attached the other way around (4-3 instead of 3-4), which would make no difference if Spermidine were symmetrical. This form of juxtaposition is unusual from a plant synthesis perspective. It shows, in this instance, that it can get hold of either end of the stick.
Spermidine itself is shown for comparison, although it seems to be ubiquitous throughout many Genera and must also be present in Honesty. Note that it is asymmetrical, with four carbon atoms on one side and only three on the other.
LBX is identical to Lunarine apart from a CH2 bridge spanning the two nearer nitrogen atoms, thus making a six-membered ring with two nitrogen atoms in it at the meta positions (being
pyrimidine, compare with the two isomers
pyrazine where the nitrogen atoms are at the para position and with
pyridazine with the nitrogen atoms at the ortho position.
LBY is identical to LBX apart from the ketone part of the benzofuran rings being replaced by ⋅H⋅OH.
Initially there was considerable confusion caused by the unusual multi-membered rings of the Lunaria alkakoids, confusion which may persist to the present day. Rumours of further alkaloids within Honesty such as Lunariamine and Numismine cannot be substantiated by any readily-found structural formulae. Although the reports are ubiquitous, no structural formulae are to be found, only empirical formulae.