I find it is sometimes informative because specific illustrators often use the serpents or dragons in consistent ways.
For example, in one of the very old English herbals, every time there is a snake next to the plant, the text includes a notation that it is for snake bite.
In Palatino 586 there are many animals and people surrounding the plants. At first I couldn't figure out what they represented, but after going through all the plants three times I realized that most of them represent how the plant is used, in somewhat metaphorical ways. I couldn't figure out all of them, but once you see how this particular person illustrated them, some of the meanings become clear.
In others, the text doesn't offer any help (some don't have text), but if you can find three or four dragons next to identifiable plants, you can sometimes figure out their meaning.
[As an aside: Another convention that is very common is to create a root that looks like a snake for plants that have snaky roots and which often (because of the snaky root) have names like "snake root", "viperina", etc. The VMS has three plants with snakes in the root. I think they mean different things though. Two of them have snakes that are the root, but the third (the one that I suspect is Cuscuta) has snakes interlaced with the root (they are not part of the host plant, but intertwined with it in the same way the parasitic Cuscuta entwines itself with its host).]
Unfortunately, there is only one dragon (if it is a dragon) closely associated with a plant in the VMS, making it difficult to look for patterns. I sometimes wonder what was in the missing quire that might have made things more clear.
For example, in one of the very old English herbals, every time there is a snake next to the plant, the text includes a notation that it is for snake bite.
In Palatino 586 there are many animals and people surrounding the plants. At first I couldn't figure out what they represented, but after going through all the plants three times I realized that most of them represent how the plant is used, in somewhat metaphorical ways. I couldn't figure out all of them, but once you see how this particular person illustrated them, some of the meanings become clear.
In others, the text doesn't offer any help (some don't have text), but if you can find three or four dragons next to identifiable plants, you can sometimes figure out their meaning.
[As an aside: Another convention that is very common is to create a root that looks like a snake for plants that have snaky roots and which often (because of the snaky root) have names like "snake root", "viperina", etc. The VMS has three plants with snakes in the root. I think they mean different things though. Two of them have snakes that are the root, but the third (the one that I suspect is Cuscuta) has snakes interlaced with the root (they are not part of the host plant, but intertwined with it in the same way the parasitic Cuscuta entwines itself with its host).]
Unfortunately, there is only one dragon (if it is a dragon) closely associated with a plant in the VMS, making it difficult to look for patterns. I sometimes wonder what was in the missing quire that might have made things more clear.