The truth is, witches and wizards can -- and do -- use both magical and non-magical plants in their day-to-day lives. There are scores of non-magical plants used in even some of the most complex potions! Because of this, using a plant in a potion is not enough on its own to make the chosen herb be considered magical. After all, salt, bits of armadillos, horses, and crocodiles are ingredients in magical potions. Likewise, having an innate useful effect (healing or otherwise) does not make a plant magical. To qualify as magical, a plant must either exhibit odd behavior or it must have unique abilities. These abilities can be of the plant itself -- like Creeping Ivy’s ability to move at will -- or it can grant a unique ability to anyone who uses the plant, such as the gill-bestowing Gillyweed. 

There is one thing that magical plants possess (or can possess) that no non-magical plant can, however. Sentience. This is a bit of a thorny issue both inside herbological circles and in the academic wizarding world at large, but there is certainly evidence to suggest that at least some magical plants are sentient, or able to perceive the world around them and act in response. Now, don’t be thinking that your Mimbulus Mimbletonia is able to engage in philosophical debate with the Flitterbloom you have it next to! However, there is no denying that some magical plants seem a little too savvy or aware of their surroundings to be natural. We have trees that punch, vines that bite and snap, and many plants that almost seem to have personal preferences or personalities, like the mandrake. Skeptics of this theory try to attribute these quirks to complex root systems or hairs allowing the plants to sense a nearby presence and react alongside our tendency to projection of human characteristics onto things. For example, the touch-me-not plant does not shrivel up because it is afraid or repulsed, as would be the case if a human reacted in this manner. This is simply an inherent defense mechanism for the plant that is triggered by certain events. It is not a choice or mental reaction in any way, though it may appear to us to seem that way.

In any case, it is certainly hard to be sure. Indeed, magic has not advanced far enough for herbologists to be able to tell if plants are in any way aware of their own existence, or can feel anything at all, but in some cases it does seem that way. 

Unique abilities: When identifying magical plants, unique abilities can be split into two groups. The first includes abilities plants may bestow upon humans that they do not naturally possess, such as breathing underwater, becoming invisible, or becoming incredibly lucky. The second group concerns the abilities a plant demonstrates on its own, such as the ability to defy gravity, growing like a normal plant while not being made of natural plant materials, being able to pollinate or reproduce in strange ways, suddenly catching fire, or mimicking speech, just to name a few.

Odd behaviour: When identifying magical plants, “odd” behaviour can include unnatural movement, an unnatural growth rate, a strange diet, or actions that imply sentience.