There are two major reasons to cite both text and image sources used in a research paper or project.
1. Giving credit to the owner of words, ideas, and images.
Copyright laws protect everyone's original ideas and creative work when they are published either in print or on the internet. In order to give authors their due credit, you cite the sources where you found their words and ideas. If you use a person's exact words, you should put the words in quotation marks and indicate the source where you found them using the citation style prescribed (links on the right). If you are not copying another person's exact words but using their ideas in your paper, you are restating or paraphrasing their words and thoughts. You still need to cite the source, but without quotation marks.
2. Adding credibility and further information sources to your paper.
Citations linked to references used in your paper provide substance and credibility to your writing. Anyone who reads your paper will know that your consulted reputable or scholarly information sources in the process of formulating your analysis and composition. The bibliography will also enable anyone interested in learning more about your topic to find additional information by reading books and/or articles you have cited.
Landscape architecture projects and research papers should always adhere to a consistent writing and documentation style. There are a variety of styles that used in academia. Ask your professor which style is required or recommended for the course before you begin your project and then familiarize yourself with that particular style. If no specific style is required, choose one and use it consistently throughout your project or paper.
Specific style guides available online.
Best Practices for Attribution from Creative Commons is a useful tool for identifying best practices for attributing CC-licensed content. (Creative Commons Wiki)