Easily confused with :
Dyer's Bugloss (Alkanna tinctoria), Bugloss (Anchusa officinalis) [which are also sometimes called 'Alkanet' along with Green Alkanet!] and with
Greater Forget-me-not (Brunnera macrophylla) which can grow together.
Many similarities to : Bugloss (Anchusa arvensis) which also has deep-blue flowers but the leaves of Bugloss are twisted and contorted and more bristly and hairy.
Slight resemblance to :
Alkanet (Anchusa officinalis) but that has purple rather than bright-blue flowers.
Superficial resemblance to :
Garden Anchusa but that has larger flowers between 15 - 25mm across and a tuft of white hairs in the centre.
The flowers themselves, with their smallish size, and five bright-blue petals resemble those of many
Uniquely identifiable characteristics
Distinguishing Feature :
The only species in its Genus, Pentaglottis.
It is found in hedgerows, waysides and the borders of woods. It is native and rapidly spreads, but also frequently escapes from gardens, but cannot grow in acidic soils; for it is calcicolous. It has a reputation to spread, particularly along hedgerows. Removal is difficult for the thick tap-root extends downwards up to half a metre and removal of all of it problematic. It will re-appear next year.
NAPTHOQUINONES in ALKANETS
Alkannin and a minor related constituent of Green Alkanet called
Alkannan (and its steroisomeric partner
Shikonin (not shown) are red dyes found in both Green Alkanet and in
Alkanet. Both of these are Napthazarins / Napthoquinines.
The tap root of Alkanet (and Green Alkanet) is thick. Alkanet (and Green Alkanet) root extracts are used as purple and burgundy coloured dyes, and as varnishes for fine wood goods such as violins. It seems probable that the name 'Alkanet' derives from its use as a blue dye, where the extract from the roots is made blue by an alkali hydroxides (and made crimson again by addition of acids). The name 'Anchusa' for some other similar flowers derives from the Greek anchousa meaning 'paint'.
Your Author does not know whether Naphthazarin itself is present in Green Alkanet, but it is in the un-related
Dyer's Alkanet (Alkanna tinctoria), although it is in the same family as Green Alkanet (being Boragibaceae) it is not in the same Genus. Naphthazarin is a purple dye. The chemical formula is normally shown as the top diagram, but it exists as a resonance-hybrid, with the Hydrogen atoms being shared alternately (at ultra-high speed) between the two adjacent oxygen moieties (naturally altering their properties as it does so), with consequent sharing of electrons around the fused aromatic rings, leading to a more stable molecule. This probably also alters its colour absorption spectrum.
According to one old source, the red colouring product from alkanet root consists of two separate compounds, one,
Alkannic acid, turning green by the action of alkalis, the other,
Anchusic acid (aka
Alkanna Red and
Anchusin), turning blue. Both of these acids form characteristically coloured salts. However, later sources suggest that the two compounds are identical! There is something strange here, the same substance cannot yield differing colours under the same conditions and it is likely that some of the substance has been inadvertently modified into another compound.
Pigments and dyes are not identical, the first being in-soluble in the medium by which it is delivered, the second being soluble. A lake pigment is a dye that has been precipitated into a powdered colourless substrate. Aluminium hydroxide, because it is transparent, is often used as the substrate to receive the dye to make it into a lake pigment. A purple lake pigment can be obtained from the extracts of Alkanet root. Alkannin is soluble in organic solvents but almost insoluble in water. In the former it is a dye, in the latter a pigment (and a lake pigment when deposited into a transparent powdered substrate).
Other constituents in the Alkanets include some pyrrolizidine alkaloids such as
7-AngeloyRetronecine, several derivatives of Alkannin such as
Alkannin IsoValerate and
Alkannin Angelate and fatty acids such as Linoleic Acid, Palmitic Acid, Oleic Acid and Linolenic Acid (Gamma).
Many members of the Borage Family (and Daisy & Dandelion Family) contain (mostly poisonous) pyrrolizidine alkaloids, the only variation being which particular ones out of the hundreds already known. Here it is Triangularine and its hydrogenated derivative Dihydrotriangularine which are structurally similar to the pyrrolizidine alkaloid Senecionine, but with a broken ring and a few other alterations or to Heliosupine which already has a broken ring.
Triangularine is also known as 6-Angenyl-9-SarracinylRetronecine.