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Toxic sap from Africa鈥檚 desert rose tree is used to coat arrowheads (Image: Michael Melford/National Geographic Creative)

I love English country gardens and churchyards full of yew trees, foxgloves, native monkshood and snowdrops. They mark the seasons, and are utterly charming.

They are also so utterly deadly that they should be better known as cell toxins, heart-stoppers and neurotoxins. The whole of the English yew (Taxus baccata), bar the plump, red flesh around its seeds, is poisonous. Foxgloves (Digitalis purpurea) can stop hearts dead, whereas monkshood (wolfsbane or aconite) opens the doors of sodium ion channels in cells, poisoning neurons while 鈥渙pening minds鈥�. Even the tiny snowdrop (Galanthus) can be highly toxic.

My list is only a subset of the 360 plants inside Phytomedicines, Herbal Drugs, and Poisons, a compendium of the homicidal, hallucinogenic and healthy. Few books can have scarier disclaimers. The inside page warns that some plants can cause 鈥渄eath, serious intoxication, severe allergies and other harmful effects鈥�, and that nothing in the book should be interpreted as 鈥渁 recommendation to experiment鈥�.The authors and publishers also stress that they cannot 鈥渂e held responsible for claims arising from the mistaken identity of plants or their inappropriate use鈥�.

鈥淢ost of the English yew is poisonous, foxgloves can stop hearts dead 鈥� even the snowdrop can be toxic鈥�

As botanical compendiums go, it鈥檚 a rollicking read. It is also highly political in the UK at least, where rows about 鈥渓egal highs鈥� and herbal drugs have been reignited after UK home secretary Theresa May pledged a clampdown, amid controversy about the scientific evidence behind the move. And from the mind-altering seer鈥檚 sage (Salvia divinorum) to the tranquillising valerian (Valeriana officinalis), there are plenty of 鈥渉ighs鈥� and herbals to choose from here.

Plants go back a long way in traditional medicine. Records left by the Assyrians, Babylonians and Sumerians some 4000 years ago show that they not only used herbal medicines but possibly had clay-tablet prescription pads.

We have since learned about the chemical basis for the purported benefits of plants such as lavender (useful for de-stressing) and garlic (which can be used as a blood thinner, antiseptic and more). In addition, modern medicine can now harness old killers for good: the yew yields the cancer drug paclitaxel, while foxgloves give us the heart drug digitoxin.

Under duress, I鈥檝e eaten the Bengali appetiser fried neem leaves (the bitterest dish on Earth), and tasted a more palatable papaya curry appetiser. Neem (Azadirachta indica) is a natural insecticide that is used to treat stomach ailments and intestinal parasites, whereas papaya is a digestive, and turmeric in curry contains curcumin, which has anticancer and antimicrobial properties.

The section on poisons puts the English killers in perspective. Laburnum is the worst culprit in Europe thanks to seeds that attract children. And the odollam tree (Cerbera odollam) from Asia and the Pacific has bitter fruits containing glycosides that inhibit ion channels in heart muscle. The fruits are said to have killed more people (through suicide or murder) than any other plant poison. In Africa, toxic sap from the roots and stems of the desert rose tree is still used on arrows for hunting game.

Phytomedicines is beautifully illustrated, with an accessible reference section, and it fulfils the authors鈥� pledge to provide a general reference book for pharmacists and lay public alike. I鈥檓 less sure whether it can do all that while offering a first port of call in an emergency. But it is still a welcome addition to any budding botanist鈥檚 bookshelf, and a potent reminder of our complex relationship with plants.

This article appeared in print under the headline 鈥淜illers, kicks and cures鈥�