Utah State University offers Plants and Landscapes classes. This class offers eight sections. They include an introduction, overview, summary, plant life cycles class, nomenclature, plant physiology, annuals and perennials, and landscape use. The videos in the courses can be streamed or downloaded.
The Annuals and Perennials course at Utah State University offers seven classes for the gardener or landscaper. They include an introduction, overview, summary, annuals, perennials, sustainability, and woody plants. Combined with the course above, it is a great overview of plant knowledge.
Offered by Brigham Young University, Planning and Preparing Your Garden has sections on soil preparation, planting for a defined space, and different gardening strategies. There is some minimum software requirements for the course and you'll need to make sure your machine is capable. There is a left side link to a software setup to make sure your machine can run the program.
The Growing Vegetables, Fruits, and Nuts program at Brigham Young University is available online and is very different than most distance-learning courses. It offers a grading system, so those in the class can monitor their progress. This course offers three lessons and students are encouraged to work on their own gardens while keeping a journal for supplemental learning. The class features how to plant nut trees, appropriate gardening tools, problems in growing fruits, and vegetable growing.
Tufts University has two Agriculture Science and Policy courses that work on more commercial applications than backyard gardening. However, proper horticulture techniques go a long way in giving a great education. According to the website, "This course highlights the relevance of natural resource conservation for ensuring healthy agricultural, food and environmental systems, as well as the various approaches for implementing it. This course, the first of two semesters, focuses on soils, water, air and energy. The second semester delves into plant nutrients, plant- pest interaction, crop breeding, and livestock production."
These classes are a great way to expand your horizons in gardening or refresh your memory on some of the horticulture you may have forgotten. They are all able to do be done at your leisure.
Brigham Young University, Tufts University, and Utah State University. Links are given in subheadings.