Leaf analysis can be one of the best approaches for plant classification as leaves are plane surfaces which can have distinct color, texture and shape.
Article Plant leaf classification using multiple descriptors: A hier...
Naglaa Al.abide one idea i can share not exactly plant classification, it's about leaf classification. you can take high-resolution image of leafs and then putting them on MATLAB you can perform classification as well as you can find the leaf-diseases also by performing classification between effected leaf image and non-effected image in MATLAB.
If you check UCI machine learning repository in their you can get a dataset called "iris" contain more than one lakh leaf image that also you utilize through WEKA.
Would I violate RG's policy if I listed my work on classifying grape varieties by leaf shape? The RG administration has already issued 2 warnings to me, so that I do not give links to my work. So I will say that they are there and you can find them yourself if you want.
you take A set of plants of different types. you measure, for each plant, four things: sepallength, sepalwidth, petallength, petalwidt, as well as the name of each plant. put the results obtained in a .txt file and apply the classification methods.