The path of sacred plants includes the knowledge and applied use of the plants, trees, and fungi that induce an altered state of consciousness.  This altered state may include stupor, intoxication, excitement, or hallucination; the altered state achieved is then used for a specific application such as healing, divination, communicating with spirits, or trance.  This path is a sidestep away from the more traditional herbalist's path; much of the information that applies to one path will apply to the other, but those on the sacred plant path have chosen to specialize in this subset of the herbalist's art.  Someone on this path will naturally come to know the many uses of sacred plants that go beyond their ability to alter consciousness, uses that include healing, curing spiritual ailments, relieving pain, and magical applications. 

This path has seen a revival of interest in recent decades though the use of these plants and their derivatives have been a part of many cultures for thousands of years.  Many European and North American authors have done extensive work researching the chemical makeup and the historical uses of these plants, tempting minds towards experimentation and spiritual exploration via this medium.  Many serious practitioners take issue with this undisciplined exploration saying that yes, there are spiritual traditions that make use of these herbs, and each culture has prescribed ways to handle them; exploration for its own sake takes the use outside of a very particular context, which negates much of the value that could be gained since the substance is not being used in the same way or for the same reasons.  Others say that the effects these plants have are unnecessary, a crutch, and that they aren't needed to reach enlightenment or be a spiritual practitioner (even going so far as to dismiss the use of these plants in a modern context altogether); traditional practitioners who administer these plants to those they are treating do so only to fool gullible uneducated savages.  Yet others tout sacred plants as the ultimate spiritual experience, the means by which the human mind is fully opened to the reality of the life and the universe.  I fall somewhere in the middle of this debate.  I neither see these plants as the ultimate means to an end, nor do I see them as unnecessary or irrelevant.  To me they are independent entities, not resources to be tapped, and must be approached with a great deal of respect (as well as a measure of humility) before any work is to be done with them.  They are not suited to every job, or to every person.

One term used to describe these plants is " entheogen ."  It was coined in 1979 by scholars including Carl Ruck and Jonathan Ott .  The word comes from two Ancient Greek words, entheos and genesthai ; translated the term means "that which causes God (or godly inpsiration ) to be within a person." (1) On the meaning of the term entheogen , Ruck stated: 

"In the strictest sense, only those vision-producing drugs that can be shown to have figured in shamanic or religious rites would be designated entheogens , but in a looser sense, the term could also be applied to other drugs, both natural and artificial , that induce alterations of consciousness similar to those documented for ritual ingestion of entheogens ." (2)

The term is used herein to refer to any plant or fungus that is used to create a change in consciousness, specifically a change associated with spirit-work or shamanic techniques.  Other writers have not limited the word's application and include substances like alcohol and chemicals, as well as including recreational use in their personal definition. 

This path, like any spiritual discipline, has its pitfalls.  Addiction, injury, and even death are not unknown; author Dale Pendell calls this "the poison path" (3) and we are dealing with many poisonous and toxic substances.  Some are illegal, or their derivatives are.  A mistake on this path may show up much faster than in many other disciplines.  Like other disciplines, this is not an equal opportunity path; not everyone is suited to this, or needs to be.  Also, not everyone who uses sacred plants at one time or another is expected or needs to become a serious practitioner, and indeed many people should not.  This work demands a particular sort of person, and they will generally find themselves on this path as a matter of course regardless of past involvement with any of these plants.   

There are a great many benefits to this work.  The plant spirits have a unique perspective on the world, and working with them allows us to share that perspective; the presence of these spirits in your life can be a great blessing as they are valuable teachers and partners.  These are some of our most potently magical plants and in skilled hands can have remarkable effects.  With proper training, their medicinal benefits can also be known.  The required discipline is tempered with a great deal of enjoyment; several sacred plants bring pleasure just through their presence, and growing and nurturing them is relaxing and heartening.  The chemical effects of these plants allows a person to achieve states of mind not accessible to them in any other way; not everyone can easily gain deep trance or heightened awareness, and the aid of a sacred plant in this can be very useful.  

Sources:
1, 2 http://en.wikipedia.org/wiki/Entheogen
3. Pendell , Dale; Pharmako /Gnosis: Plant Teachers and the Poison Path( 2005)