
There is a foot of snow on everything outside, and the temperature is hovering around 20°F, so there isn’t much to say about gardening. Perhaps this is a good time to warn everyone that those healthy vegetables that we grow can sneakily try to poison us. A bit of background is in order. At the end of the growing season each year, if it has been a good growing season and, if there are plants still producing small amounts of vegetables, I make vegetable soup for canning. Sometimes it is vegetarian with odds and ends of vegetables plus lots of tomatoes. Sometimes it is a meat-based soup. It is particularly good with the remains of a ham if it is available, lentils, and whatever dried beans that are in the cupboard.
This is the tale of a vegetarian vegetable soup. I cleaned, peeled, and prepared all the available veggies. The mainstay of this soup is always summer squash, both yellow squash, and zucchini, as there are so many of them. I diligently cooked it for hours, and when it was soup I tasted it for seasoning. It was the most horrible bitter brew that I had ever concocted. This was a large kettle of soup and throwing it away wasn’t my first choice. There are some ways, as any cook will tell you, to remove odd tastes or excess salt from food. Adding something starchy like potatoes removes the salt. It didn’t work with the bitterness in the soup. Something acidic often works with bitterness in veggies like kale. That didn’t work either. A little bit of sugar to mask the taste? It was still horrible. I eventually consigned it to the compost heap.
Years later, I eventually found out that I was exceedingly lucky in that I was not able to mask the bitter taste of the soup. The bitterness indicated the presence of a poison. Yes, those zucchinis had turned poisonous. The culprit is a toxin known as cucurbitacin. It is found more generally in wild members of the Cucubitaceae family, which includes cucumbers, gourds, melons, squashes, and pumpkins. It is believed that it is produced to protect these plants against the depredation of insects or herbivores. Of the 900 or so members of the Concubinage family, only about 100 contain this substance. The curcubits grown from modern seed all contain traces of cucurbitacin, but not in sufficient quantities to be detected or cause illness. Melons, squashes, and pumpkins still produce cucurbitacin but it is confined to the roots, leaves and stems of plants grown from the modern seed. If a bitter melon of any sort occurs the problem is increased levels of this toxin.
There are circumstances that can increase the toxicity in curcubits that are grown in the garden. One is environmental stress such as heat or drought. Lack of proper fertilization can also cause a rise in levels of toxicity. Bitter cucumbers can sometimes be saved by removing the ends or peeling the fruit. If the cucumber is bitter throughout it should be discarded. Burpless cucumbers are supposedly cucurbitacin-free. It is this substance that causes minor irritation to the stomach that results in burping. Burpless varieties include Burpless, Carmen, County Fair, Diva, Fanfare, Garden Sweet, Marketmore 76, Slice More, Sweet Slice, Sweet Success, Sweeter Yet, and Tasty Green.
Those “volunteer” squashes that appear in the garden are not always safe to eat. Modern seed contains a genetic component that suppresses the production of cucurbitacin. If you grow summer squash, including zucchini, you will see that it is quite promiscuous. All members of the Cucurbita pepo group of squashes can cross-pollinate. This group includes acorn squash, delicata squash, gem squash, ornamental squash, pattypan squash, spaghetti squash, yellow crookneck squash, yellow straight neck squash, and of course zucchini. Cross-pollination can cause the production of seeds that will produce fruits that have a higher concentration of cucurbitacin than is safe. (One of the best squashes that I have ever grown was a volunteer. The parentage was unknown.) It is not advisable to save squash seeds, especially if you are growing more than one type of squash. No squash seed is considered to be stable. All squash seeds however are edible.
Ornamental gourds are especially dangerous. None of them are edible. While they have little flesh and are bitter and are not likely to be the first choice for the dinner table, they can cause other problems. If they are grown with other squash they can cross-pollinate. The resulting seeds can produce plants that have fruit that is high in toxins while looking like a normal squash. Fortunately, again the cucurbitacin is readily detectable in the bitterness of the flesh. However, from 2012 to 2018, 353 people in France consumed some form of ornamental gourd either purchased or as a result of cross-pollination in the garden and sickened from them. The symptoms of cucurbitacin poisoning are unpleasant but rarely fatal. The toxins cause intestinal upset. These include bloody diarrhea, vomiting, moderate to severe gastric pain, low blood pressure, gastric bleeding, and dehydration.
Potatoes are another sneaky vegetable. The potato normally contains glycoalkaloids (alpha-solanine and alpha-chaconine.) The concentration is not high enough to cause problems, but several factors can cause an increase in the levels of these substances. One is the “greening” of the potato from exposure to light or sun. The green color is not the problem as it is chlorophyll. It is however an indication that glycoalkaloids are present as they form along with the chlorophyll. Any green on a potato should be meticulously removed before cooking. Potatoes that have begun to sprout should have the sprouts and eyes removed as they are another source of high concentrations of these toxins. The safest thing to do is peel the potato if there is growth or greening. Discard severely affected potatoes.
Symptoms of poisoning from potatoes include a burning sensation in the mouth and various gastrointestinal reactions. Nausea, vomiting, cramping, and diarrhea can occur. In severe cases, adverse neurological effects may be present. Consuming enough glycoalkaloids to bring this about these more serious efficts is unlikely because of the bitter taste of the potatoes.
Beans, both the green variety and dried beans, contain phytohaemagglutinin. This toxin is destroyed by heat, so it is important to cook beans thoroughly. The levels of this chemical vary in the different types of beans. Pinto beans and navy beans have the lowest concentration, and red kidney beans have the highest. Black beans also have a fairly high concentration. Green beans have a low amount, but the amount of raw green beans consumed should be limited. It is safe to lightly cook green beans if a crunch texture is preferred. Canned beans of any sort are safe as they are pre-cooked. Dried beans should be cooked thoroughly. Dried beans cooked on the stove are safe, but cooking them in a crock pot may not allow a high enough temperature to destroy phytohaemagglutinin. Kidney beans especially should be boiled for 10 minutes, and the water drained before cooking in a crock pot. Soaking the beans for 5-8 hours will also remove toxins.
Phytohaemagglutinin poison will cause vomiting, diarrhea, and abdominal pain. These symptoms will usually cease in 3-4 hours without treatment. It can also interfere with cellular metabolism and cause the clumping of red blood cells, but that is unlikely to occur from eating beans.
Curiously, several sources suggested that children be kept away from uncooked kidney beans when doing art projects or other similar activities. Apparently, the fear is that they will ingest enough of the poison by putting the beans in their mouths.
It is to be noted that bitter lettuce, while not palatable, is not poisonous. The chemicals involved are lactucin and lactucopicrin, which have a mild sedative effect. They are also found in endive and other bitter greens. Not all veggies are out to get you.

Wild Cucumber