From 23°27′ N on down to 23° 27′ S, one does not have to worry too much about where one's next meal is coming from .. there is always something growing. When one gets out of the tropics though, we have this thing called 'Winter', and that means that one needs to take extra steps to make sure that one has food to eat. Typically, one would use preservation techniques to store some food items: dehydrating, fermenting, pickling .. and in the modern age, canning, vacuum sealing and freezing.
My preferred method for storing food over the months where it is difficult to grow is to look for edible plants that can be preserved without refrigeration, or even the use of a canning jar, as getting replacement lids for jars might be impossible in case of a real emergency .. and those lids have a limited shelf life. We still do some canning, but only those things that cannot be preserved any other way. Like our ancestors who thrived in this land before us, our go-to storage staples are flour corn, beans, and winter squash .. and a host of root vegetables.
Once one begins diving into the world of edible roots that can be grown in the temperate zones, one will encounter a bewildering spectrum of bulbs, corms, rhizomes, and tubers .. underground starch storage tissues used by plants to survive those winter months, that make great food for humans .. except when they are toxic, of course .. and that is why it is important to be able to tell the difference, and the good news is, it isn't hard!
Both bulbs and corms have a very similar appearance: A fleshy underground structure that encloses the stem, roots emerging from a region at the bottom, opposite the stem. Both will produce additional, smaller bulbs or corms from the parent plant through vegetative propagation.
In order to tell if one has a bulb or a corn, cut into the mass: If it has a series of layers surrounding the immature flower bud in the center, it is a bulb, and not a corm.
There are a great number of edible corms - Taro and Water Chestnut come to mind - But there are a great number of poisonous ones as well, like Crocus and Gladiolus: these are frequently found in domestic flower gardens. There is no easy identification method for determining if a corm is poisonous or not; it is best to have the plant positively identified while it still has its vegetation intact.
Fun Fact: The three stigma in the center of each crocus flower are harvested for saffron, the world's most expensive spice. At the time if this writing, saffron was priced at about $15/gram.
Fortunately, there is a simple test to determine if a bulb is toxic. Once one can determine that one has a bulb, and not a corm, it gets very simple. There are very few true bulbs, and all are toxic to some degree or another, with the exception of alliums: the chives, garlics, leeks, shallots, and onions. When cutting into the mass of the suspected bulb, one should notice the distinct aroma common to all alliums: the scent of allicin.
Allicin is a thioester of sulfenic acid, with a chemical formula of C6 H10 O S2 .. so one can see that this compound is manufactured by the plant using just Carbon, Hydrogen, and Oxygen .. just like retinol (vitamin A) .. except for those two sulfur atoms right there at the end: If one's soil does not have sufficient sulfur in bioavailable form, one's alliums will be low in allicin. They will not smell as strongly, taste as potent, or provide as much medicinal benefit. I discussed natural ways to bring sulfur to one's soil surface in the Mar 17,2021 blog post 'Dynamic Accumulators'.
Scent alone should be sufficient for an identification, but in case one has a diminished sense of smell for some reason, one may taste the bulb (without swallowing) .. does the bulb have an onion or garlic flavor? Note that the flavor of allicin is not a 'hot' flavor, exactly. If one notices 'heat' like the heat from a spicy pepper, and no onion flavor or scent, the bulb is poisonous, and you likely have an allergy to it, as well.
Hailing from the South American Andes mountains, with an 8,000 year long history of cultivation, the best know tuber on planet Earth today is .. drumroll please .. the Potato! Like corms, tubers are revealed to be one entire mass when cut - no layers. Unlike corms, tubers do not have a distinct region opposite the stem where the roots grow .. tubers seem to put out roots wherever they please.
One will be pleased to discover that there are a host of edible tubers to be had, aside from the aforementioned spud, and many make for interesting additions to the garden for reasons beyond their edible roots. Dahlias make some of the most stunning flowers in an ornamental garden, but their tubers are crisp and sweet .. the flower is also edible, if one can bring one's self to destroy such a thing of beauty. The daylily hemerocalis fulva presents another example of an 'ornamental' garden favorite, with a long history of cultivation for its tubers and delicious flowers - after one's first taste, one may leave off planting annual lettuces entirely.
Many tubers are toxic, and even parts of the tubers that we eat on a regular basis can be hazardous - when a potato is exposed to light, it begins to develop a compound called solanine (from which the genus Solanaceae gets its name). Yams, from the genus dioscorea have high concentrations of calcium oxalate just under their skins - making it prudent to peel them under water, to reduce the risk of contact dermatitis. There is no quick and easy identification trick for tubers to determine toxicity: again, one must observe the plant while it still has its foliage.
Imagine for a moment: A person being afraid to try eating potatoes, because there is no easy way to tell if a tuber is poisonous just by looking at it .. silly, isn't it?
Tubers have eyes. What I should say is, some tubers have 'eyes' - buds appearing along the wall of the tuber that may become plant stems under the right conditions. There is one more root crop that I have failed to mention, up until this point, and it is now that I should remedy that oversight: Let us talk about rhizomes. A rhizome is a fleshy, subterranean stem, segmented with nodes, from which either plant stems or roots may emerge. one may easily distinguish between a rhizome and a tuber by the segments: Tubers do not have them; the tissue surrounding a tuber's 'eyes' is generally smooth.
Some commonly consumed rhizomes include ginger and turmeric root .. but unknown to most, the canna root is a very heavily consumed rhizome as well .. aside from being excellent in its natural state (requires about 30-45 minutes of boiling before the tough outer skin can be peeled) the members of genus Cannaceae, the Canna Lily (once again, not really a lily) are harvested for their starch, used to make the 'glass' noodles popular in Southeast Asian cuisine, and are high on my list of reliable, easy to grow calorie crops.
Before I take my leave, I would like to redirect the reader's gaze to the first two pictures in this article. One picture is of an edible plant, and the other is a picture of a plant that will cause nausea, cramping, dizziness, and vomiting when consumed. Without being able to smell the difference between these two plants, can you tell which is which?