The use of unmanned aerial vehicles (UAVs) and computer vision for automating farm operations is growing rapidly: time-consuming tasks such as crop monitoring may be solved in a more efficient, precise, and less error-prone manner. In particular, for estimating productivity and managing pests, it is fundamental to characterize crop regions into four classes: (i) full-grown trees, (ii) tree seedlings, (iii) tree gaps, and (iv) background. In this paper, we address the classification of images from citrus plantations, acquired by UAVs, into the previously mentioned categories. While Deep learning-based methods allow to achieve high accuracy values for classification, explainability remains an issue. Therefore, our approach is to run an experimental analysis that allows to derive the effects of different parametrizations (involving descriptors, classifiers, and sampling methods) when applied to our citrus dataset.