Fruit & Vegetables A Beginners Guide to Edible Weeds

Ah, the dreaded 'deadly' nightshade! How come I can eat them and not die, then? © JPM, 2022.

Names

Members of that illustrious family of plants, the Solanaceae, blackberry nightshade belongs to the genus Solanum (S.) and are relatives of common commercial crops such as potato, tomato, eggplant and tamarillo. They have, for the last century or so, carried a dishonourable reputation: they are the purportedly 'deadly' nightshade, the consumption of which is sure to be instantly fatal. Happily, those who hold such a view of these very common weedy shrubs are incorrect in their identification; deadly nightshade, otherwise known as greater morelle (or morel, but I do not want to confuse it with the mushroom), is the botanical plant Atropa bella-donna, although it is still a member of that same, wider Solanaceae family. More on that below.

Consequently, the naming of blackberry nightshades is often a perilous task, complicated by no shortage of botanical confusion between individual species. With that in mind, we can identify, at least generally, several popular species and their most common English names: glossy nightshade, American nightshade or wild currants (Solanum americanum); blackberry nightshade, black nightshade or petty morelle (S. nigrum); velvet nightshade (S. chenopodioides); green-berry nightshade or morelle verte (S. opacum); woolly or red nightshade (S. villosum); turkey berry or devil's fig (S. torvum); and the small-flowered nightshade (S. nodiflorum), a plant only genetically distinct from S. americanum and S. nigrum! There are more names and species than these, obviously, but they are the ones that will be most frequently encountered whilst wild foraging for this plant in most English-speaking climes.

Americans might also want to keep an eye out for one of their other native species, S. ptycanthum, noted for its purple- or maroon-tinged undersides of young foliage; this plant will not be otherwise covered here. There are scores of other edible (and inedible) species native to Europe, Africa and Asia, such as S. scabrum and S. macrocarpon, which will also not be otherwise covered below other than in the necessary caution at the conclusion of this article.

Habitat and Range

Blackberry nightshades are widely distributed across Australia and the world, being found on every continent save Antarctica. Many species are natives of Africa and the Americas and were mentioned in ancient herbal medicine texts such as Dioscorides' Tractatus de Materia Medica (or in its original Greek, Peri hulēs iatrikēs), dating back to the 1st century C.E, thus implying its ancient Mediterranean and Near-Eastern range as well. Due to the great difficulty of botanically distinguishing the various species, botanists remain in heated debate as to the natural range of many varieties of this plant; some have even argued that Solanum americanum originated in Australia (Deane, 2011)!

Figure 1. Illustration of Solanum nigrum from a 6th century palimpsest (over-written) manuscript of Dioscorides' de Materia Medica, a plant utilised since ancient times. Pinterest.


Generally, blackberry nightshades prefer moist, sub-tropical and temperate climes, although some species such as S. americanum and S. torvum are common all the way up the east coast as far as Cape York and other tropical areas besides. Blackberry nightshades will grow in all kinds of environments, although they prefer rich, preferrably high-nitrogen, agricultural soils. They can be found popping up in orchards, fields, parks, gardens, sidewalks, culverts, agricultural rows and bushland across most of the east coast, Tasmania, select inland regions and southern Western Australia. They will grow in full sun or full shade alike. When I was in the New England (Armidale) region in January 2021, about a month after good rains, blackberry nightshade (probably S. nigrum) was so prolific it was the single most common understorey shrub in that entire national park. Due to thousands of other native plants of the Solanum taxon being present in Australia, the distribution of each of main named species above will be shown on the maps.

Figure 2. Distribution of glossy nightshade (S. americanum). Some of these data points are undoubtedly confused with S. nigrum. Atlas of Living Australia.


Figure 3. Distribution of common blackberry nightshade (S. nigrum). Some of these data points are undoubtedly confused with S. americanum. Atlas of Living Australia.


Figure 4. Distribution of velvet nightshade (S. chenopodioides). Some of these data points are likely confused with S. nigrum. Atlas of Living Australia.


Figure 5. Distribution of the native green-berry nightshade (S. opacum). Atlas of Living Australia.


Figure 6. Distribution of devil's fig (S. torvum). Atlas of Living Australia.


Identification

Key Identifying Features

• Shrubby weed growing between 60-120 cm (2-4 ft.) tall
• Leaves of variable shape, usually 3 to 10 cm in length, spear-tip shaped to slightly oval, with smooth or jagged edges
• Leaves and stems usually green, but occasionally have tinges of purple
• Flowers appear on stalks emerging 1-3 cm (1/2 - 1 in.) away from the nearest leaf node or stem joint
• Flowers in clusters of 1-10 on each stalk, sometimes in 'tresses' (like cherry tomatoes)
• Flowers have five white (rarely, purple-tinged) petals, sometimes swept back, with an obvious yellow core
• Flowers self-pollinate by vibration (usually wind)
• Flowers turn into unripe green berries slightly smaller than a pea
• Unripe berries have green flesh surrounding the 20-80 tiny seeds
• Ripe berries usually turn black (glossy black, S. americanum & S. nodiflorum; matte black, S. nigrum & S. chenopodioides), but occasionally chlorine green-yellow (S. opacum & S. torvum) or red (S. vellosum)
• Ripe berries have purple (rarer, yellow or red) flesh surrounding the 20-80 tiny seeds

Blackberry nightshades are not terribly difficult to identify and have several stand-out features, especially in contrast with the true deadly nightshade (Atropa bella-donna, see Look-alikes below for full comparison of these plants). They are, first of all, a common weedy shrub usually 60-120 cm in height, often branched from firm, stout stems that often have a faint fuzz of white hair on them. Leaves are spear-tip shaped to oval, and there is significant variation in the edges, from smooth to serrated.

Figure 7. A stand of glossy nightshade (S. americanum) in a park at Chiswick. © JPM, 2022.


Figure 8. A smaller, single plant (probably S. americanum) displaying more serrated-type foliage. © JPM, 2022.


Figure 9. The black-purple stems of this damaged-but-recovered S. americanum displays the significant genetic colour variation within this plant genus. © JPM, 2022.


Figure 10. Foliage undersides (S. americanum, pictured) show no significant colour change, except the American species S. ptycanthum. © JPM, 2022.


Figure 11. Another example of leaf variation, probably S. americanum. Note the fuzz on the stems. © JPM, 2022.


Figure 12. Leaf and colour variation. This is possibly S. nodiflorum but the glossy berries might suggest S. americanum instead. © JPM, 2022.


Figure 13. Example of leaf variation. This S. americanum has distinctly serrated leaf edges. The stem hairs are barely evident just below the flower buds. © JPM, 2022.

Flowers appear on stalks that sprout 1-3 cm (1/2-1 in.) away from the closest leaf nodes (see also figure 12 above). Flowers are small, usually 5-10 mm (1/4-1/2 in.), with five white or purple-tinged petals, and five green sepals on the connecting calyx. The flowers have a central yellow 'core' of five very tight stamens, usually completely concealing the single pistil in the centre. The flowers are bisexual and easily self-pollinate, quickly forming small trusses of unripe green berries. Berries will turn black when ripe; some species are a glossy black and others a matte black, a few of the species turn pale yellow or red when ripe. Ripe berries have a consistent flesh colour inside coating the seeds; if it is still green it will still be toxic. Fully ripened berries are edible if they are not bitter.

Figure 14. A typical flower stalk emerging from a glossy nightshade (S. americanum). Note the five petals and five-sepalled calyx (closed buds), yellow anther 'core' and these ones actually show a protruding pistil tip. © JPM, 2022.


Figure 15. Not my best photography, but the purple tinge on the petals of these glossy nightshade (S. americanum) flowers is obvious. © JPM, 2022.


Figure 16. Flowers drop off and the ovary grows into these tiny, smaller-than-a-pea unripe berries (S. americanum, pictured). The five sepals on the calyx is very obvious. © JPM, 2022.


Figure 17. It might look ready, but the one black berry on this glossy nightshade (S. americanum) truss was still green inside. This is not an example of a matte berry (see below). © JPM, 2022.


Figure 18. Ripe and ripening berries of glossy nightshade (S. americanum) with a surprise interloper. © JPM, 2022.


Figure 19. Note the matte black on this common blackberry nightshade (S. nigrum). Atlas of Living Australia. © M. Fagg, 2010.


Figure 20. Again, matte black berries are very distinct on the velvet nightshade (S. chenopodioides). This species is fuzzy all over, similar to many native bush tomatoes, also from the Solanaceae family of plants. Atlas of Living Australia. © R. Callaway, 2016.


Figure 21. The green-berry nightshade (S. opacum) barely changes colour when it is ripe. Atlas of Living Australia. © Bellacorella, 2021.


Figure 22. Devil's figs (S. torvum) have perhaps the most distincly lobed leaves, and the fruit turn yellow-orange when ripe. Atlas of Living Australia. © Anonymous, 1997.


Figure 23. Woolly or red nightshade (S. vellosum), common throughout Africa, has distinct red-orange (occasionally yellow) ripe berries. Wikimedia Commons. © S. Lefnaer, 2019.

Culinary Uses

These plants surprisingly did not make the culinary weed lists compiled by either Apelian (2021) or Duke (2001). Other wild food foragers speak highly of the berries (e.g. Low, 1991; Deane, 2011; Grubb & Raser-Rowland, 2012), a testimony with which I wholeheartedly agree. The fresh, fully ripe berries, that is, fruit that is completely black (or yellow/red for species that ripen to those colours) with no tinges of green inside or outside, are usually very tasty, having a fruity, grape-like burst followed by a lingering, sweet tomato aftertaste. All species mentioned above have black fruit except the ripe, pale-chlorine yellow berries of S. opacum and the red-fruited S. villosum. Any ripe berries from this family of plants that taste suddenly bitter or are still green inside should immediately be spat out and the plant neglected or harvested whole for medicinal uses (see below).

Fruit may be eaten fresh in-situ, cooked into pies, pastries, jams and sauces, and dried/frozen for later use. Blackberry nightshade was frequently used by colonists, especially on the frontiers and during Australia's frequent droughts and colonial supply shortages (Low, 1991: 99). Where these plants occur abundantly, there are no shortage of berries. These plants are also commercially cultivated for fruit in many African countries (especially Kenya). Urban environments only rarely have more than half a dozen plants occupying an area, making berry foraging mere trail snacks.

Figure 24. What to expect inside the fruit of a glossy nightshade (S. americanum). Ripe fruit are very soft and burst easily after picking. Notice the dark purple penetrates the entire fruit and there is virtually no green. © JPM, 2022.


Figure 25. Insides of a ripe green-berry nightshade (S. opacum). All yellow, little green. Atlas of Living Australia. © G. Steenbeeke, 2020.


The double- or triple-boiled leaves, especially young leaves, are commonly referred to in the literature as a popular green in sub-Saharan Africa (Ojiewo et al., 2013) and south-east Asia, especially Papua New Guinea (Lim, 2013 VI: 320; Low, 1991: 98; Deane, 2011). Some African species, such as S. scabrum, have been selectively bred so as to greatly increase their foliage production over fruit or flowers (Ojiewo et al., 2013: 10-11). Leaf toxicity is also greatly variable from region to region, from 80 mg/kg to 170 mg/kg of fresh plant material, and the human palate can detect the bitter taste of the toxic alkaloids at approximately 140 mg/kg (Ojiewo et al., 2013: 11) and caution is advised when preparing leaves for consumption. I have not yet tried any culinary preparation of any of this plant's foliage due to the availability of other, superior edible greens such as purslane (Portulaca oleracea), sow thistle (Sonchus oleracea), dandelion (Taraxacum officinale), fat hen (Chenopodium album) and various wild mustards (Brassica spp.), all of which do not require double- or triple-boiling to prepare safely. Ojiewo et al (2013: 11) do mention, however, that the African nightshades selectively bred for greenery are excellent dietary sources of bioavailable iron, containing up to 100% RDI (recommended daily intake for an adult) of iron in a 100 g serve.

Medicinal Uses

Blackberry nightshade, especially the specific species S. nigrum, has been utilised for millenia for a variety of preparations as the ancient testimony of Dioscorides' de Materia Medica attests. Many of the blackberry nightshade plant extracts exhibit antimicrobial activity, lower blood pressure and have anti-inflammatory modes of action (Lim, 2013 VI: 321-323). Other research has justified the plant's narcotic (painkilling) properties resulting from activity of its steroidal glycoalkaloids solasonine, solamargine and P-solamargine (0.0-2.0% w/w in unripe berries and foliage); there are also some steroidal saponins present (Gruenwald et al., 2000: 101-102). Gruenwald et al. also mention that ingestion of small quantities of medicinal preparations of the plant can greatly reduce stomach ulcers caused by excessive aspirin use (see also Lim, 2013 VI: 408).

Bruised fresh leaves of S. americanum and S. nigrum may be applied topically as a poultice to alleviate inflammation, rheumatism and skin infections such as ringworm, burns and ulcers; many tropical cultures also use the decoctions of the plant roots topically to treat conjunctivitis and other eye infections (Lim, 2013 VI: 323-324, 411-413, 438).

Herbal preparations start by collecting leaves while the plant is flowering; the whole plant while flowering; or whole plant with berries intact (unripe or ripe). The foliage or whole plant is then air dried and boiled in water (Gruenwald et al., 2000: 101). The following preparations and dosages are recorded by Gruenwald (2000: 102):


Look-alikes

As a young plant, it is possible to confuse various blackberry nightshades with other plants of the wider Solanaceae family, as well as some other common edibles such as fat hen (Chenopodium spp.), amaranth (Amaranthus spp.) and some smaller nettles (e.g. Urtica urens). Wait for plants to flower/fruit to ensure positive identification if you are not certain.

For American, European, African and Asian readers, it is very possible to confuse this plant with the potentially fatal, and real, deadly nightshade (Atropa bella-donna); deadly nightshade is not found in Australia or New Zealand. This plant was introduced as a potential look-alike in my article on fat hen (Chenopodium spp.) but I will repeat the caution here in its entirety with that same helpful illustration. At younger stages of growth, deadly nightshade can be more easily confused with blackberry nightshade. Wait for flowers to appear for easy identification! Firstly, deadly nightshade has very distinctive, trumpet-shaped purple-mauve flowers. Second, its five long green sepals (together, the calyx) extend well past the periphery of the fruit. In contrast, blackberry nightshades (all Solanum spp. mentioned above) have five-petalled, star-shaped, white or white-purple, tomato-like flowers, and its green, five-sepalled calyx never extends beyond the fruit itself; some species of blackberry nightshade have curled sepals and others have sepals that hug the top part of the fruit but never extend and stick out beyond the fruit skin itself. Thirdly, the fruiting stalks for Atropa bella-donna also appear from the leaf node (where the leaf stalk meets the plant's stem); blackberry nightshade consistently sprouts its fruiting stalks about 1 to 3 cm (1/2 to 1 in.) below or above the closest leaf node.

Figure 26. Note the purple-mauve, trumpet flowers and protruding calyx which marks Atropa bella-donna as the real deadly nightshade. Wikimedia Commons, Public Domain.

Caution: Toxic Alkaloids!

Blackberry nightshade leaves and unripe berries are high in solasonine, mentioned above, a steroidal glycoalkaloid and a natural narcotic (painkiller) with side effects including nausea, vomiting and intense sweating. A toxic, but not fatal, dose is approximately 200 mg/kg fresh plant weight or 1,000 mg/kg dry plant weight (Ojiewo, 2013: 11). The human palate can detect the bitter taste of this alkaloid at concentrations of approximately 140 mg/kg (Ojiewo, 2013: 11). This toxin is, fortunately, water soluble and will almost completely leach out in double- or triple-boiled preparations of the greens; discard the liquid unless you are planning medicinal preparations mentioned above. Ripe fruit which tastes bitter should be eaten sparingly or not at all. As with all wild foods, enjoy in moderation!

Further Reading

Atlas of Living Australia, "Solanum americanum." [LINK]
Atlas of Living Australia, "Solanum chenopodioides." [LINK]
Atlas of Living Australia, "Solanum nigrum." [LINK]
Atlas of Living Australia, "Solanum nodiflorum." [LINK]
Atlas of Living Australia, "Solanum opacum." [LINK]
Atlas of Living Australia, "Solanum villosum." [LINK]
Deane (2011), "American Nightshade: A Much-Maligned Edible." [LINK]
Duke (2002), Medicinal Herbs, pp. 96-97.
Grubb & Raser-Rowland (2012), Weed Forager's Handbook, pp. 35-39.
Gruenwald et al. (2000), "Black Nightshade." PDR, pp. 101-102.
Lim (2013), "Solanum americanum." Edible Medicinal Plants Vol. VI, pp. 318-325.
Lim (2013), "Solanum nigrum." Edible Medicinal Plants Vol. VI, pp. 395-418.
Lim (2013), "Solanum torvum." Edible Medicinal Plants Vol. VI, pp. 429-441.
Low (1991), Wild Herbs, pp. 98-99.
Ojiewo et al. (2013), "Exploiting the Genetic Diversity of Vegetable African Nightshades," Bioremediation, Biodiversity and Bioavailabilty 7(1): 6-13 [Pdf download LINK]