The topic is very obscure and you will get many many different answers, and opinions. Online there's mostly random articles, also contradicting each other, and so on.
What's most important is to decide what is needed from a "anti-depressant". Some herbs offer depressant-like effects, for example Valerian.
It's sedative and induces sleep, symptoms which might go hand in hand with general depression. On the other hand, St. Johns Wort has showed anti-depressant qualities.
Well, not trying to promote any of the two plants at the moment, the point is to try to find EXACT effects you are looking for. Some are anxiolytics, some (anti)-depressants, etc.
The next step would be to research the available info. Since I did research some plants quite extensively, my suggestion is to look for scientific studies, as the only source of information that's been consistent with the results and suggestions.
For example:
I'm looking for an anti-depressant plant species.
Found a study researching anti-depressant effects from some common herbs in rats (not humans, but pretty close, right?)
https://www.researchgate.net/publication/44572521_Antidepressant-like_effect_of_Salvia_sclarea_is_explained_by_modulation_of_dopamine_activities_in_ratsResults suggest that Salvia sclarea has the best properties for that purpose.
The next step would be to find out WHY and HOW it happens, and if it would be of any use to you.
Essential oils are mostly the "active" components of these aromatic herbs, so maybe find a profile for the plant in research:
http://ijagcs.com/wp-content/uploads/2013/05/828-831.pdfThe most abundant component of the oil seems to be Linalyl acetate, so the next step would be to research if it's the molecule responsible for the effects,
and if it is, find some other plants containing it.
It is a lot of work, but for me was the only sure way to find out what I was looking for. I saved tons of material on the same topic (plants and essential oils that affect GABA and other receptors), but now I got way too much material to research. When I'm finished hopefully, I can compile it and share.
And yes, some herb components react with medications and other stuff, which should be thoroughly researched also, before doing and experiments

Also - while we're on the topic, I don't buy the whole "professionalism" in the medicine field. They suggest us to use chemically-derived products, which have been proven to have serious side effects or haven't been used by human population long enough to know how it affects us long-term, while at the same time keeping a blind eye on the research of the plants components which might be just-as-effective, if not more effective. If they do find such an effective, naturally occurring alternative, they will try to synthetitize is and add a bunch of other stuff to it, then present it to you in a "professional" and "scientific" way which will make you trust it more then your own instinct and ideas. If the common goal was to cure disease, I would trust the pharmacy and doctors, but I don't think that's the case to full extent.