I am trained in LA but work as a part time gardener. If you want to learn about horticulture then there are millions of books out there all for different topics.
For LA we design for planting to be self sufficient / low maintenance and come from an ecological basis so its appropriate for public realm. 'The Dynamic Landscape' is really in depth with loads of references which might be good for you to take advantage of if you have student journal access but its pretty heavy. "Naturalistic Planting Design The Essential Guide' is a really easy and nice book to learn the same basics in less depth. ''The planting Design Handbook' is a standard must read for any LA. Then you have all of Piet Oudolfs books, Henk Gerritsens, Beth Chattos, and Noel Kingsburys. Then loads of cool niche books if you are into wildflowers or self seeders; or grasses, or climbers, green roofs, green walls, rain gardens, woodland / shade, clay, gravel etc.
Personally I would start with Nigels essential Guide, then Nicks Handbook, then the Dynamic. Once you have read every book there is you can challenge yourself to Henks Essay on Gardening haha