I have both the Jacke books and the Crawford book. Jacke, vol 1, is a very good in-depth how-to-design book, and if I could only get one book, I think it would be that one. You can find lots of info
online on any particular plant species that interests you, but I find that my own physical book is more necessary when thinking about design approaches. You can find the Jacke books on ebay, sold separately as well as a set.
I am sure that the Portland library will have all three of these, plus the Whitefield book. Maybe trying before you buy would help you make this decision.