Have you ever cut into a plum tomato and [for a moment] thought it was a pepper?
Or had a similar moment with the seed patterns of eggplant and tomatillos?
Maybe you've walked through a vegetable garden and noticed how certain flowers resemble each other?
Solanaceae, commonly known as nightshade, is a fascinating and diverse family of plants comprised of 102 genera and 2800 species, many of which are globally significant sources of food.
Popular edible genera and species:
Solanum: potato (S. tuberosum), tomato (S. lycopersicum), eggplant (S. melongena)
Capsicum: bell pepper and chili pepper (C. annuum)
Physalis: tomatillo (P. philadelphica)
lesser edible species:
ground cherry/cape gooseberry (Physalis peruviana), goji berry (Lycium barbarum), tomarillo (Solanum betaceum), pepino melon (Solanum Muricatum), naranjilla (Solanum quitoense), wonderberry/sunberry (Solanum retroflexum), Morelle de Balbis (Solanum sisymbriifolium).
Nearly half of all nightshade species are found in the genus Solanum, including two important foods: potato and tomato. The potato species, with over 4,000 varieties, is the world's fourth largest food crop, surpassed only by rice, wheat, and corn. It possesses all of the vitamins and minerals necessary for human survival with the exception of vitamin A and D. Think about this the next time you add butter, milk, or sour cream to potatoes: you're creating a nutritionally complete food.
The potato tuber seems an anomaly in this large, varied family of predominantly fruit (tomatoes, eggplant, and peppers are botanically fruits, but for culinary purposes are considered vegetables). That's because the plant is genetically programmed to direct energy to forming tubers instead of fruit. Only 8% of the potato's genes are responsible for this trait, the other 92% of its DNA is shared with the tomato.
Economically, the tomato can give its tuberous cousin a run for the money— 2 billion dollars worth in the US market alone. Not bad for a fruit that started as a wild green berry in the mountains of Peru (also the birthplace of the potato) and thought to be unfit for human consumption for a span of its existence. Even after domestication in Europe, it was regarded as a mere curiosity to some, while others thought them (as a Paduan physician declared in 1628) “strange and horrible things”. But that was a long time ago and we no longer find the tomato so disagreeable. Well, at least not all of the time.
From July through October, homegrown and small farm raised tomatoes are celebrated with cult-like vehemence. For the rest of the year, when our only choice is commercially grown fruit, we are left with... strange and horrible things. How are these even related and, for the love of Flavor, if we can (insert any modern technological advancement), why can't we buy a tomato from November through June that isn't an abomination? For an age-old lament, you would think that the answer is more complicated than it actually is— what it really comes down to is money. The commercial farmers in South Florida, who grow 90% of out-of-season supermarket tomatoes in the US, don't get paid for flavor, they get paid by the pound. In this monopoly, flavor is inconsequential— profit comes from yield, uniformity, shippability, and shelf life. It's a grim laundry list that the other stakeholders— the commercial tomato breeders— must fill in order to get their piece of the pie. In doing so, they have bred the flavor right out of the tomato.
But there is hope...
Earlier this year, two separate papers were published on tomato genetics that could have a positive impact on commercially grown tomatoes by satisfying the consumer's yearning for flavor and still maintain the grower's bottom line.
The focus of one paper, published in the journal Science, is a random gene mutation in tomatoes that turn them uniformly red. Older varieties, like the heirlooms, turn red from the blossom end to the stem, some even remain green around the stem when fully ripe. Although the mutation was discovered 70 years ago and has since been deliberately bred into modern varieties to make them more attractive to consumers and easier for growers to determine ripeness, it was the authors, led by Ann Powell, a plant biochemist at UC Davis, who discovered that the missing gene inactivated by the mutation is responsible for the alluring aroma and flavor of a ripe homegrown tomato.
In another paper, the genome of the tomato was decoded for the first time by an international consortium of 300 plant geneticists from 14 countries. Shortly after it was published in the journal Nature in May, a surprising discovery from the study— that tomatoes possess a whopping 35,000 genes— made headlines. That's about 7,000 more genes than you or me but it doesn't mean that tomatoes are more complex, they just manage their cells differently.
The monumental work, nine years in the making, illuminates a cheaper and speedier path to improving every aspect of the tomato— from flavor, to disease resistance (lacking in heirloom varieties), to nutrition, to yield— and the ability to isolate these traits separately. The information about the evolution and pathways contained in the genome sequencing also has implications for other fleshy fruits that share tomato characteristics.
All of this groundbreaking information may seem like it's clearcutting the way for genetically modified tomatoes. That's been tried already, back in the 1990's, and failed due to consumer confidence. Instead, it facilitates the selective breeding of new varieties, both for the home garden and commercial farms. But when will we see change? According to a member of the consortium, Professor Graham Seymour of the University of Nottingham, in a BBC article:
"I only work with a couple of companies but I know that they are putting through some of these new traits and they are going to their elite lines - but all tomato breeding companies will be taking this up now so you would expect to see a number of new products over the next 3-5 years."
tomato poached in lime basil oil
stuffed with mozzarella curds and mascarpone
tomatine sauce: fermented green tomato and tomato leaf
More than tomatoes and potatoes and other good things to eat, nightshade has a dark, unsavory side that begot its name. Meet the shadiest members:
datura (Datura stramonium)
belladonna (Atropa belladonna)
henbane (Hyoscyamus spp.)
mandrake (Mandragora spp.)
These genera played a prominent role in early medicine and continue to be important today. During the Renaissance, Venetian courtesans dilated their pupils with belladonna, the source of the alkaloid atropine, to make them appear dreamy and seductive. The vain application of the past inspired the more practical modern use of atropine in routine eye exams.
The superstitious minds of Medieval Europe shrouded nightshade in mystery, magic, and the occult. Mandrake, whose forked root sometimes resembles a human form, was believed to release a deadly shriek when pulled from the earth and was only harvested through a complex ritual that involved tying the plant to a dogs' tail on a moonlit night. The witches of the time inhaled henbane smoke to induce hallucinatory trances necessary to cast spells and summon spirits. Many of these plants were included in their legendary flying ointments for the sensations of lightness that they produced.
Earlier still, datura was revered as a sacred visionary plant by ancient civilizations of the world and used ceremoniously to induce prophesies. Henbane was commonly used in Druid and Viking rituals, as evidenced by the seeds found in their graves.
History, folklore, and literature are all guilty of romanticizing deadly plants, but nightshade's deadly aspect is no joke. These genera are host to a potent chemical soup of psychotropic alkaloids that in the right dose can treat a variety of ailments from motion sickness to Parkinson. In the wrong dose, they are capable of inducing hallucinations, comas, and death. Solanaceae plants produce these alkaloids and other compounds as chemical defenses against predators and environmental threats. but if you think they are limited to the medicinal species, think again.
Everything we eat has consequences. The most blatant example is chili pepper, a food that we willfully eat that causes us both pleasure and pain. The pleasure comes from a release of endorphines. The pain comes from the volatile compound capsaicin that, in a twist, has the ability to relieve pain.
Though not a food, tobacco (Nicotiana tabacum) is an important cash crop that produces the alkaloid nicotine, whose harmful and addictive nature has been well documented. But how many abstainers know that it is also present (in lesser degrees) in eggplant, tomatoes, and potatoes?
Have you ever experienced an itchy or burning sensation on your tongue after eating eggplant? That's oral allergy syndrome, caused by protein histamines that affects sensitive individuals.
And those green spots on potatoes? Those are harmless chlorophyll, but they indicate something insidious just under the surface: the presence of solanine, a poisonous alkaloid that can cause severe nausea, and even death.
Just as science shines new light and understanding on naturally-occurring plant compounds and their implications to our health, it also exposes myths.
The strange and horrible tomato, once feared for its association with the dark side, is now known to contain beneficial phytonutrients, even as an increasing part of the population sensitive to their alkaloids is choosing to exclude them, and all nightshades, from their diet.
Solanine has been long believed to be the culprit that kept us from consuming tomato leaves. But as Harold McGee pointed out in a 2009 article in the New York Times, solanine belongs to the potato species, while the tomato's is tomatine, which "appears to be a relatively benign alkaloid". So, while it may not be a good idea to indulge in a heap of tomato greens, a few aromatic leaves used as an herb is likely harmless.
Perhaps the most misunderstood and controversial members of Solanaceae belong to the Solanum nigrum complex. Solanum nigrum, commonly known as black nightshade, is a morphologically distinct species and there are at least 30 other distinct Solanum species that are bundled into this complex. To quantify them all under the dark umbrella of black nightshade taints them with the perception that they are all deadly poisonous when, in fact, they are not. At least, not all of the time. And that's where the confusion begins.
Here, too, solanine seems to be the problem— or more accurately— the varying degrees of concentration among the species. Many (too numerous to list) have a long history as significant food sources, primarily in Africa and Eurasia. Most often, it's the leaves that are gathered and cooked as greens. In some cases the ripe berries are consumed as well. Unless we are willing to sift through a maze of mind-numbing toxicological data on the individual species, there is very little practical information available. Even so, conclusions given by plant scientists are typical to this:
"the development of toxic levels of these alkaloids is dependent on their growth under certain conditions or in certain localities, and even on the age of the plants concerned. Other reports suggest that the amounts of poisonous 'principles' vary greatly with climate, season and soil type." (Edmonds and Chweya,1997)
Could this be a case of poisonous terroir?
The fear and uncertainty surrounding black nightshade, at least in North American, prevents even the adventurous from gathering and consuming wild species— every field guide lists S. nigrum as toxic. But there is a cultivated species that was introduced in the early 1900's by plant breeder Luther Burbank, whose ripe berries are reputedly safe to eat.
Burbank claimed to have hybridized his 'Sunberry' by crossing S. guineense with S. villosum , and created Solanum burbankii, “a new food plant from a poisonous family”. In 1909, Burbank sold the rights to the seeds to John Lewis Childs, who rechristened it 'Wonderberry' and promoted it with extravagant claims as "the greatest garden fruit ever introduced ". Suspicion was cast when horticulturists claimed that it was nothing more than common S. nigrum. Controversy raged until the 1950's when the wonderberry was proven to be a distinct species native to South Africa. It was never known whether Burbank was aware of this or if it had been inadvertently introduced to his experimental gardens. Nevertheless, the damage was done and fear of black nightshade cast the wonderberry into obscurity. In recent years, wonderberry has been resurrected by seed companies and gardeners interested in 'new' heirloom varieties. Sometimes it is listed as the hybrid S. burbankii, sometimes as the correct species S. retroflexum, but by all accounts it is safe to eat the black ripe berries (green are recognized as poisonous), and by many accounts, they are delicious.
roasted eggplant and smoked potato custard
fire-roasted pepper petals
Ever versatile, Solanaceae contributes more than food and drugs— it enriches our lives with beauty and scent through these ornamentals plants:
petunia (Petunia spp.) most widely grown ornamental nightshade • 35 species • flattened tubular flowers • available in many colors from white to black (dark purple) • spreading habit makes them popular in hanging baskets.
flowering tobacco (Nicotiana spp.) various flowering species of tobacco • small tubular star-shaped flowers open at dusk • older varieties are more scented than modern.
datura (Datura spp.) aka: angel's trumpet, moonflower, thorn apple • large erect trumpet flowers • produces spiny seed pods • highly toxic.
brugmansia (Brugmansia spp.) closely resembles datura, but with pendulous flowers and woody stems • grown as trees in the tropics • strongly scented • highly toxic.
The etymology of Solanaceae is unclear— there is conjecture that Sol- refers to their preference for sunshine and heat. Most genera originated in warm climates, where they grow as perennials. In cold climates, unless protected, they must be treated as annuals. Although they love growing in the sun, the flowers of these ornamentals only release their alluring scent at night. This trait allows them to attract nocturnal pollinators and, perhaps, contributed to the naming of "nightshade".
Among the edible species, tomatoes, peppers and eggplant are the most widely cultivated by home gardeners. They're certainly omnipresent in my vegetable patch, along with tomatillos. They are easy to grow if you provide them with rich soil, room to breathe, and at least 6 hours of sunshine a day. Potatoes require a little extra care as they need to have additional soil hilled up around them as they grow to allow tubers to form along the stem and to protect them from sunlight that triggers solanine.
I've always allocated space in the garden to experiment with new plant varieties. This year, it was occupied by three nightshade: purple tomatillos, groundcherries, and Morelle de Balbis.
The purple tomatillos got a late start and didn't fully ripen before the first frost, but I was able to harvest a decent crop of the green variety before they succumbed to the same fate.
Groundcherries were a delight (for the squirrel and slugs too). When ripe, their papery green husks turn brown and they fall to the ground. The berries within are edible when green and taste similar to tomatillos. They turn yellow when ripe and become sweet with a flavor reminiscent of pineapple. They'll definitely be on the roster next year.
The Morelle de Balbis were formidable plants to grow— the stems, leaves, and husks are covered with fierce thorns that like to grab onto clothes and hair, and prick exposed skin. The husks surrounding the berries make them appear to be physalis, but they belong to the genus solanum. They break open when the fruit ripens, exposing red berries that taste like a blend of tomatoes and plums, and take on sweet cherry notes as the fruit ages.
pineapple honey glazed groundcherries
cherry honey glazed Morelle de Balbis
lime tomatillo tuile sheeps milk gelato
sweet cicely chamomile
Even as I put my garden to rest for the year, I'm already thinking ahead to next.
I already know that nightshades will take up most of the real estate. I'll put the tall tomatillos towards the back, the low-growing groundcherries in the front, where they'll have room to sprawl. The potatoes will grow in a row along the wall that will retain the soil that I'll pile on them as they grow. There will be peppers, both hot and sweet, and petunias in hanging baskets on the porch, flowering tobacco in the border by the back door to perfume the night air.
I look forward to growing two new-to-me varieties: wonderberry, an edible member of black nightshade (see above), and naranjilla (Solanum quitonense), a shade tolerant plant that produces acidic orange berries, reputed to taste like pineapple and lime.
And yes, there will be tomatoes, as many as I can fit. They'll get the spot with the best soil and the most sun because the tomatoes that grow there will likely be the best that I eat all year. Maybe someday, with a push from science, that will no longer be true.