Not having looked at it I would assume the material pathing is broken/incorrect.
-Where in your wars or crysis directory is is located?
-Within those files find the associated textures.
-Within the editor place down the plant, as an object not from a vegetation layer, press M and then from the
top toolbar select "get material from selection."
-Look at the name of the material then find the file labeled the same in your objects directory (if the modder is being typical it should be in the same folder as the objects .cgf file. If it is not move it there. Also make sure it is named the same thing.
-If the plant has multiple variations labeled with a prefix the name of the material should be the prefix. For example Cannabis_1, Cannabis_3, Cannibis_low would all use the material file labeled "cannibis.mtl."
- Locate the objects .mtl file if you already haven't and open in your preferred text editor (notepad works well enough.)
-Within that file you will see references to directory locations. These are the locations of the texture files that the material needs. Look at the directory locations and make sure the path is correct. if it is not then correct it.
-Save edited .mtl file
Example .mtl file and correction
<Material MtlFlags="0" Shader="Vegetation" GenMask="268525568" SurfaceType="mat_grass_tall" Diffuse="0.45882356,0.45882356,0.45882356" Specular="0,0,0" Emissive="0,0,0" Shininess="10" Opacity="1">
<Texture Map="Diffuse" File="Mods/mwll/Game/Objects/objects_mwll/Natural/Plants/Marsh_Grass/cattails.dds">
<PublicParams BackViewDep="0.40599999" BackDiffuse="0.56999999,0.75999999,0.37" BackDiffuseMultiplier="0.62800002" blendWithTerrainAmount="0.64700001" bendDetailFrequency="6.79" bendDetailLeafAmplitude="0" bendDetailBranchAmplitude="-1.88" bendDetailPhase="62.200001" BackShadowBias="0.82200003"/>
Note the directory reference: File="Mods/mwll/Game/Objects/objects_mwll/Natural/Plants/Marsh_Grass/cattails.dds
This should point directly to that .dds texture. If it does not change it. if the texture is instead located in your general textures directory (game/textures/stuff/cattails.dds.) you would change the .mtl to reference that file location instead. So instead of Mods/mwll/Game/Objects/objects_mwll/Natural/Plants/Marsh_Grass/cattails.dds it would be game/textures/stuff/cattails.dds
Sorry for the long explanation I'm just trying to be complete.