Is it left to right? I feel like I remember it being that way but it's been awhile since I needed that info, so I'm not sure. For instance when building things the item on the left would get it first. Does it also read the plants that way? If so, does having your plants in a certain order help get more desirable results?

Having your plants in a certain order only matters for things like the Fairytales and buildables, where things go to the leftmost item or the fairy harvests the leftmost item.  The exception is the butterflies, where a caterpillar will attach itself to the plant furthest to the RIGHT.  No idea why.

But the garden isn't "read" to determine whether wildlife comes or not.  Placement doesn't affect attraction, there is no particular order to get better results - just put your plants how you like them.  There are players who insist that you need the mushroom to the left; others will insist you need it to the right.  But it just doesn't work that way :)

Thanks so much Tracey and for the info on caterpillars, I've actually never heard that one! Good to know! So if I have a Ventus Quatriflorus out, I don't need to worry about placing the Cattus Peloflorus deterrent to the right of the Ventus Quatriflorus, I can just place them anywhere? I always just assumed since items come farthest left that the garden read like a book, attraction flowers, then the deterrent after each attracting one. I'm sure people have experimented with that, but it really makes no difference??

@ Tracey - thanks for the info about caterpillar attaching itself to rightmost  plant... I didn't know that.. learn something new  in here  every day