If you enjoy foraging, you may have heard of the Universal Edibility Test. This is a way of deciding (in an emergency) if a plant is fit for human consumption. The test was devised by the US military to systematically test a part of a given plant if you are not sure if it is poisonous or not. Read on for details of how to conduct this test on plants you collect.
A Word of Warning
The first thing to say is that this test can be used on any plant you know is edible just to get used to doing it.
That way, you can learn the technique without poisoning yourself. With that said, you need to now separate your chosen plant into its various parts; the leaves, the buds, the flowers, the stem, the roots, the berries, or fruit and then decide how you want to test it.
For example, you may want to try the leaves raw as a salad or you may want to cook the leaves like spinach. Or perhaps you would prefer to try boiling the root or eating the berries raw.
It is really important to test the food slowly, one step at a time to allow any symptoms to show themselves. Wear gloves when picking plants you do not recognise and sensible long-sleeved shirts and trousers for protection so you avoid thorns, stings, and contact with anything poisonous. Are you ready to test?
- In situ when you first pick the plant, smell it. If it smells awful, this usually tells you not to eat it. The Stinking Lily plant has a poisonous bulb and foragers say it smells vile. Berries that taste bitter are also a guide to them not being good for your insides but let’s leave tasting until later.
- Cut the plant with a knife to observe the colour of the sap. If it is milky white, this is a sign that the plant is poisonous so discard the sample and any remaining pieces. This is true for almost every plant with white or milky-coloured sap so it is good to know this if you forage regularly. You won’t waste time taking the plant home with you! Remember to carefully wash your knife and disinfect it to remove any leftover poison from the blade.
- Now here comes the difficult part. Your plant has passed the first 2 tests but next, you need to empty your stomach by fasting for about 8 hours. This will be really difficult if you are out in the wild and have just had an accident but this just ensures that any poisonous reaction comes from the food tasted, not something you ate last night that was after its sell-by date. You can drink water but not tea or coffee or anything except water.
- The elbow test is the first place you apply the piece of your chosen plant after 8 hours of fasting. Place a portion of leaf, root, or flower on the skin on the inside of your elbow and hold it in place for about 10-15 minutes. Notice if there is any sensation on your skin. Do you feel a sting or a tickling or is it just uncomfortable? If a rash appears or it turns red, this is a definite no for eating and you should discard the plant part immediately. Wash the area abundantly with water and you can safely decide this is poisonous. However, if no rash occurs and you feel quite comfortable with it on your elbow, it is time to move on to the next stage. Drink a full glass of water at this stage because you have not eaten for a while and you need to keep hydrated.
- The lip test comes next. Your lips are far more sensitive and even if there has been no reaction on the elbow, the lip may show a result when you place a fresh piece of plant material on it. Sometimes poison causes lips to swell very rapidly or you may feel a tingling, even a stinging so if this occurs remove the plant as soon as you feel uncomfortable. If there is no reaction after 10 minutes on your lip, you’re good to move on to the next test.
- The tongue test. The idea is to leave a fresh piece of plant material on your tongue for 15 minutes. Often there is no way you can stand this long due to the tongue feeling numb, uncomfortable or stinging after just a minute. This is a red flag and it says POISON so remove the plant portion as soon as any discomfort starts and discard it. Quickly rinse your tongue out with water, spit this out, and wait to see if you feel nauseous or if diarrhoea suddenly occurs. Rinse at least twice after an adverse reaction. If you feel sick, make yourself vomit. Rinse with fresh water again! If nothing happened, then you can try the next test. At this stage drink some more water and clean out your mouth.
- The chew test. You are really hungry by now but it is still not time to eat the plant. You need to bite down hard on the plant, bud, root, or whatever and then chew it for 15 minutes. Do not actually swallow the liquid just allow the saliva to start trying to digest it. This tests if any sensation occurs now. Do not be disappointed but now you have to spit out the chewed plant and then wait for another 8 hours. The advice is that sometimes symptoms develop some hours after this test so if you feel violently ill, you should make yourself vomit and rinse out your mouth. If your 8 hours fast ends and you have not noticed nausea or cramps or gone unconscious, you can conclude after this that the plant can be eaten. Remember to keep drinking water during this time so that you do not become dehydrated (as well as hungry). Finally! 16 hours have passed without eating anything so now you can either eat the plant raw or cook it.
- Time to cook the plant or eat it raw. Providing there were no adverse reactions, now you can finally try eating this plant. Use a quarter cupful of the part you want to test. So if you chose to cook the root, then prepare it (fry or boil) and eat it. Again eat only this plant for the integrity of the test and then wait for another 8 hours. So you count this as a detox day or poisoning day, depending on the result! Hopefully, after all that waiting, the plant is delicious and stays in your stomach.
If your plant has passed all the tests and you are alive and breathing, you can safely conclude that the part you tested of this plant is safe to eat, in the way you cooked it. If you want to try another part, you will have to go through the whole process again. Remember that you need to eat something soon though so save the next test for another day!
More help in identifying poisonous plants in the wild
There are 5 common signs that a plant may be poisonous. The best way to decide is positive identification but these signs may help to avoid particular plants.
- Milky or white sap when you twist or cut a leaf or stem.
- Yellow and white berries. 85-90% of white or yellow ones are dangerous for consumption. Some green berries can also be poisonous (and there are some red ones too) but statistics show that yellow and white are the most poisonous.
- An umbel shape to the flowers or seed head. Imagine an umbrella turned upside down and then you know the shape. The flower stems radiate from a central point in the umbel. Carrots have this and they are edible but so does Hemlock, which is incredibly poisonous. Be careful with umbels!
- If the leaves are dull and green, or glossy green this often indicates poison. Not always but statistically more than non-poisonous.
- A single leaf, with three leaflets – 3 leaf pattern growth. If one of the leaflets stands upright vertically and the other two in this group of three face left and right, this combination is a good indication of poisonous leaves, Not all leaves like this are dangerous but there are too many that fit the pattern.
- A bad smell like rotting or a very bitter smell often indicates the plant is poisonous.
- Many UK flower bulbs are toxic if consumed. This includes daffodils, and irises so keep these away from little hands before planting them.
Some myths dispelled
There are myths that if a plant is safe for an animal to eat, it is also safe for humans. Wrong! Birds can eat ivy berries without a problem but their digestive system can happily manage them. Dogs and cats can chew plants that humans would never dream of touching too. Most of us know never to eat holly, ivy, or mistletoe berries, as these are very toxic.
Another thing that people forget in collecting is that although one part of a plant may be edible, another part of it may be poisonous. Rhubarb leaves are toxic but the pink stem is edible. The leaves are full of oxalic acid which can cause kidney failure. Tomatoes are another plant whose fruit is edible but eating the leaves can certainly give you an upset stomach. The seeds of apples, cherries and apricots all taste bitter and unpleasant and the idea is to deter you from trying to eat them. The taste comes from a chemical called amygdalin which changes to cyanide if digested. It is not enough to kill you but it is probably best not to eat these hard seeds.
Some of the Most Deadly Plants
The main way not to be poisoned while foraging is to identify the plant without a doubt before you put it in your mouth. Join a foraging group where experts can guide you and buy a good guidebook to get you started. Here are 6 of the worst plants to avoid, so you stay safe.
Bluebells (Hyacinthoides non-scripta). These beautiful blue flowers fill our woodland areas and forests in late spring but their bulbs can be mistaken for onions. They contain a substance called glycosides which are poisonous for humans and pets and can also cause rashes on human skin so use gloves when planting them. If eaten, they can be fatal so make sure you get to a hospital as soon as possible in the event of consumption.
Deadly nightshade (Atropa belladonna), has the most beautiful red berries but the name tells you everything. Do not eat them! Symptoms can range from headaches to convulsions and your speech becomes slurred, you may have a skin rash too. All parts of the plant are toxic although opticians use an extract safely (called belladonna) which opens up the pupils of the eye, to examine them.
Foxglove (Digitalis purpurea), has tall spikes of purple flowers with spotted white interiors. They are gorgeous to look at in any garden, adored by bees and pollinators but they are poisonous to touch and can be fatal if swallowed. Wear gloves when handling them, as the poison can transfer to your eyes. Seek medical attention promptly and do not put this plant in your mouth!
Lords-and-Ladies (Arum maculatum), is also known as Cuckoo spit or Cuckoo pint. It has bright orange berries when ripe inside a leaf hood, but they can appear green or red. The colour is a warning. These will kill you! It is common in hedgerows or shady woodland.
Monkshood (Aconitum napellus) is a plant which has poisonous leaves, flowers, stems and roots. It has been used on poison spears by indigenous people in hunting. Do not touch this one as the poison will transfer from hands to eyes easily. The skin is the point of entry usually so wear gloves. The first symptom will be feeling faint or dizzy followed by an irregular heartbeat. Apparently, it tastes very bitter but this is one I will not be trying! Several species of Aconitumhave been used as arrow or harpoon poisons. You have been warned!
Poison Hemlock (Conium maculatum) causes respiratory paralysis if you eat it as the plant contains a toxic alkaloid called coniine. It can cause death so if this is eaten accidentally seek urgent medical attention
Foraging is an enjoyable activity out in the fresh air but it is really important to know your plants before you pick them. The UET can determine if an unknown plant is edible but it may poison you in the process. I recommend meeting up with expert foragers to make the most of the experience and pick fresh food without any problems.