Enlarge Person and Wild Shape interaction

Question

So, a typical question I get from people learning "how to Druids" is this:

Can I turn into an animal and then cast Animal Growth on myself to become larger?

The answer, of course, is no, because Wild Shaping doesn't change your type (Aspect of the Wolf, however, is a different story, as well as a different type of cheese when paired with Animal Growth and Awaken).

Now, I was thinking over spells (I'm working on a handbook for Planar Shepherds as well as advanced Druid-ing in general) and was thinking about Enlarge Person.

When Wild-Shaped, you retain your type. Aka, most characters are still Humanoid...just a humanoid that happens to be, say, an Elder Viper Tree. Now, I know that if you cast Enlarge Person on yourself normally, it doesn't affect your Wild-Shaping abilities.

If, however, you cast Enlarge Person on yourself while Wild Shaped...what would happen? You would, per the spell, increase a size. If "you" were an Elder Viper Tree, however, then the way it seems to me is that "you" would increase in size, effectively increasing that Wild Shape size as well.

Once you left that Wild-Shape, everything would go back to normal -- well, you might still be a large/huge humanoid, but your next wild-shape would still be within normal boundaries (aka, not enlarged).

What I'm wondering is if my conclusion here is right. The other option is that the spell would somehow enlarge "the inner you" aka your humanoid form, bypassing your current form, but that seems to be really stretching the rules here.

What are your thoughts?

Answer 1

A Medium humanoid druid that employs the supernatural ability wild shape to assume a Medium alternate form can, for example, consume a potion of enlarge person to gain that spell's benefits—like becoming Large and a +2 size bonus to Strength—while in that alternate form.

If that same (normally Medium but currently Large) humanoid (but having assumed an alternate form) druid then opts to end the wild shape effect while the enlarge person effect's duration continues, the druid resumes his normal original form except that the druid's Large as per the spell enlarge person until the enlarge person effect ends. (N.b. the spell enlarge person is dismissible.)

Were that same druid to then employ wild shape again to assume a Medium form again, he would assume that Medium form, the special ability wild shape setting his new size category overruling the ongoing enlarge person spell effect (q.v. One Effect Makes Another Irrelevant and—more tellingly—the omitted-from-the-SRD examples on PH 172).

So you know, this DM would likely rule that were the Medium humanoid druid to employ initially the supernatural ability wild shape to assume a Large or bigger alternate form, consuming the potion of enlarge person would have no effect. The enlarge person spell's description says, "Multiple magical effects that increase size do not stack" (PH 226), and the supernatural ability wild shape is, indeed, magical, therefore having the same constraints on its interaction with the spell enlarge person as any other magical effect.

However, this player wouldn't argue with a DM that ruled that because the supernatural ability wild shape sets a druid's alternate form to particular size that an enlarge person effect could work normally on that druid. That is, the supernatural ability wild shape doesn't change the druid's size but puts the druid's size at certain point and the enlarge person effect works from that point. This player may point out that this gives the druid an edge when employing size-changing magic—which is already pretty awesome—, but, since druids are involved, I don't think this ruling would even crack the top 10 list of Things I Worry About When Fighting Druids.