Easily confused with: Chinese Teaplant (Lycium chinense)but that is said to have narrow lanceolate leaves that are wider below the middle rather than widest in the middle for Duke-of-Argyll's Teaplant. From the above photographs, this looks a nonsense. In fact some authorities think that there is only, at best, a very tenuous distinction between the two which are very probably one and the same!
To add weight to my suspicion, I note that the Centre for Ecology and Hydrology PLATATT database of plants that are anything at all salt-tolerant using their Ellenberg Values, only Chinese Teaplant is listed (at an Ellenberg value=1) which means it is a slightly salt-tolerant species rare to occasional in saline soils but capable of persisting in the presence of salt. The only other Teaplant (Duke of Argyll's Teaplant) is listed with an Ellenberg value =0 - meaning that it is not at all salt-tolerant and if it does appear will not persist if subjected to saline spray or salt water (which, being within 3metres of the high tide, this specimen of so-called Duke-of-Argyll's Teaplant grows year after year...). I rest my case m'Lord: either the two are the same, or this specimen is actually Chinese Teaplant. See Salt Tolerant Species.
The flowers have some similarities to : a few others in the same Nightshade Family, such as Bittersweet, but the petals are not swept backwards, and the anthers are not in a single yellow column.
Distinguishing Feature : A large shrub with Nightshade-type flowers.
No relation to : The Duke of Argyll.
The berries are oblong, slightly irregular, and scarlet red. They contain the Carotenoids Zeaxanthin (which is yellow) and
Physalein (which is red), the latter possessing two Palmitic Acid moieties on each of the carotenoid moiety.
It is used as hedging, particularly in coastal areas. The Third Duke of Argyll introduced this plant from China in the 1730's, hence the name 'Duke-of-Argyll's Teaplant'.
The berries are variously called 'Wolfberries' or 'Goji berries' and when dried are apparently edible, despite the plant belonging to the mainly poisonous Nightshade Family (which includes cultivated edible species such as Potato,
Tomato, Aubergine and Paprika Peppers. Unripe berries may contain more toxins. Duke-of-Argyll's Teaplant does contain some toxins: Atropine, a glucopyranoside and phenolic amides, but the plant is nowhere near as toxic as the poisonous Solanaceae. Tea brewed from the leaves can have adverse biological effects if a lot is drunk. It is now legal to be sell the berries in the UK as a novel food.
The berries are collected, dried and sold commercially as Goji berries. A so-called 'health' drink called Goji juice derived from these berries is claimed to have beneficial effects, but these claims may not have been substantiated in practice. There are drug interactions when consuming these berries, both with Warfarin and with pharmaceuticals for treating diabetes and blood-pressure. They can also cause photo-sensitization of skin and exacerbate hay-fever allergies. They also contain high levels of Oxalate which may cause kidney problems. Imbiber beware!
Duke-of-Argyll's Teaplant contains, amongst many other chemicals, Scopoletin, a Coumarin that is widespread in nature along with coumarin itself and Aesculetin [sometimes spelled 'Esculetin']. It is a 7-hydroxy coumarin. This and its analogues are produced commercially by synthetic processes to act as sunscreens in suncreams because of their high absorption of the harmful ultraviolet wavelengths from the sun. In fact, on absorbing UV it fluoresces with a blue glow and was instrumental in developing spectrofluorimetric analysis of the total coumarins present in certain plants expressed as scopoletin equivalents. It is also an acetylcholine inhibitor.