Since plantain is an ambiguous term, note that I am not talking about bananas or water plantain, but herbs of the genus Plantago.
Plantain seems to grow everywhere. According to the USDA, common plantain (Plantago major L.) grows in every state of the United States, as well as Greenland and every political entity of Canada except Nunavit. In fact, according to HPSBG, you will find some species of plantain in every continent except Antarctica.
It is often regarded as a weed, probably because it spreads so rapidly. After a single plantain appeared in one of my big flower pots, it multiplied so rapidly that it soon filled the greater portion of the pot and migrated to other pots as well.
There are many species of plantain. I doubt whether it is possible to give an exact number; but according to NCBI, there are approximately 200 species.
As mentioned above, common plantain is Plantago major L. It is also known as broadleaf plantain because of its large leaves. According to Survival Plants, it also has various lesser known common names, such as rippleseed plantain and greater plantain.
The USDA treats several other species of Plantago. In contrast to broadleaf plantain, Plantago lanceolata is narrowleaf plantain. Other species are Plantago debilis (weak plantain), Plantago cordata (heartleaf plantain), Plantago macrocarpa (seashore plantain), Plantago argyrea (saltwater plantain), Plantago australis (Mexican plantain), Plantago coronopus (buckthorn plantain), Plantago canescens (gray pubescent plankton), Plantago hawaiiensis (Hawaiian plantain), Plantago maritima (goose tongue), and Plantago rugelii (blackseed plantain). These are not necessarily the most important species. I picked those that I personally found most interesting.
Some of these species are found in every state of the United States, while others have a more restricted range. For example, California, Oregon, and Washington are the only states in which Plantago maritima occurs, according to the USDA.
Plantain is easy to identify, though it is difficult to distinguish between the different species. The leaves of the omnipresent Plantago major grow in a basal rosette. Each leaf has a sturdy leaf stalk, often called a petiole, and a more or less pointed oval blade. The length of the blade is slightly greater than its width. Edible Wild Food gives 30 centimeters as their maximum length. This roughly accords with my own experience.
The venation is intriguing. One vein runs directly from the base to the tip. Others form a aesthetically pleasing arc either to the right or to the left of the central vein as they run from the base to the tip.
The inflorescence is a spike. The flowers and later the fruit closely hug the stem. Both stamen and pistil occur in the same flower. According to the University of California Davis, the fruit is an egg-shaped capsule three to five millimeters long. When ripe, it dehisces horizontally in the center and releases five to sixteen seeds.
The following remarks concern the leaves of Plantago major, though many other species are edible.
According to Plants for a Future, you may cook young leaves or eat them raw. However, this website warns that they have a bitter taste, and suggests that its fibrous strands be removed before they are used. In contrast, Kingdom Plantae suggests that you use VERY young leaves and either add them to salads or cook them as greens. It makes no mention of removing the fibers, but warns that they become stringier as they mature.
Survival Plants offers another suggestion for dealing with the tough plantain veins: chew, suck, and swallow the tender material and spit out the stringy part.
Older leaves are still edible, but less palatable. Kingdom Plantae suggests using them as stock or tea.
The chief reason for eating plantain leaves is their nutritional value. According to Kingdom Plantae, it is rich in beta carotene, calcium, and vitamin C.
A Source of Fiber
The seeds of Plantago psyllium are a source of dietary fiber. Commercial preparations with which I am acquainted are Metamucil and C-lium. The latter brand name is obviously derived from psyllium. There may be other brands that I have not noticed.
All in all, I believe that plantain is one of the blessings that God has bestowed on the earth. While some consider it a weed, it does not look weedy to me. At any rate, even the weedy weeds serve a useful purpose, contributing oxygen to the atmosphere and counteracting global warming. They also prevent erosion.