How to make a plant with images on planes (SOLVED)

The trick is adding an alpha channel to your texture map. An alpha map basically tells the game which part of the texture is visible (the parts of the alpha that are white), which part of the texture is invisible (the parts of the alpha that are black) and which parts have varying transparency (the parts of the alpha that have different shades of grey).

So to create a plant you would have to add an alpha channel to your texture map and paint the areas white that you want to be seen (so the areas of the map corresponding to your leaves) and paint the areas black that you do not want to be seen (everything inside the planes that is not your leaves, so that which is now white).

You guys are really awesome, you know? 

But I don't think I explained my problem the right way. I don't have a problem with the alpha part, that's squared away, I think... What I am having problems with is making the same UV map for all of the pieces of my mesh (I will have different images [ie. flowers and leaves] like Dara does). Hers are all mapped onto the same grid. When I try to move stuff around on my grid only the coordinates of the plane move and not the actual image, distorting the image in the 3D veiwport. 
Unfortunately, I am not so far along with my mesh to show you more of what I mean. 

Ah, I see what you mean now.

What you have to understand is that there are different types of maps. The UV map is basically a blank map (without a texture) and simply describes the U and V coordinates a specific plane of your object is mapped to. There is only 1 UV map for 1 mesh (at least in TS4).

Now your texture map is another type of map. This texture maps shows the actual textures that are going to be on your object. Your texture map is built upon your UV map. If your texture map has images of leaves on the spot where your UV Map shows the plane those leaves should be on, then your object will show the leaves that are on your texture map on that plane. An object can have more than one texture maps, this is what are the "recolours" of an object. This texture map is something that you create in an image editor and simply "load" into Blender. If you look at the bottom left of your screen it shows "leaves2.png". This image can not be edited inside Blender, it simply is what it is and you can only edit it an image editor like Paint or Gimp or Photoshop.

The best practice for creating objects is to first create your mesh and then lay out your UV-Map the way you want to. After your entire object is "mapped", you can export a line image of this UV Map to an image file and then build your texture files on top of that inside an image editor.

You can take a look at this 2-part tutorial Orangemittens wrote on mapping for a general step-by-step (simply skip the steps you already know how to do).

Phyre, generally people call the images that are laid on an object (the color and recolor images) diffuse images and calling it a texture map is going to confuse the conversation as many people use that term interchangeably with UV map. Recolorists, in particular, do not associate the creation of images in a 2D editor with the term "map" or a process of mapping. Mapping is something that is done while creating a mesh. Also, it is not true that Sims 4 items have only one UV map/mesh group. CAS items almost all have a 2 UV's per mesh, and some objects also have two UV's. Studio generally handles them for objects so you don't often have to worry about them.

KSimbleton, depending on the item it is sometimes easier to map after a diffuse image is made and sometimes it's easier to map first and then make the image conform to the map. It all depends on what you're making. In this case, because it involves alpha work and a very simple mesh, what I would probably do is create a 512 x 512 alpha image that has the flower I want and the leaf/stem parts I want. Then I would load that into Blender and map my planes over the images and size the actual mesh while I can see the image displayed on the plane. Once I got that part set up I would duplicate the leaf and flower planes and arrange the duplicates until I was satisfied with the mesh. The alternative is to create the mesh out of planes first without the benefit of seeing an image on them.

My apologies, I did not mean to confuse anyone. I'll try to adhere to the dominant terminology used on this forum. 
Also, I know objects can have more than 1 UV map. I was simply trying to explain that UV maps are unique to whatever they are mapping and diffuses are the images being recoloured. In any case, I probably did a poor job of that so thank you for clarifying it so everyone can understand.