They're currently running a Fiber & Dye exhibit (that ends March 26) that I wanted to see. The exhibit has plants used to make paper, clothing, hats, and other fibrous materials, as well as plants that are used to dye those fibers and other materials. It turns out there are a lot of natural tattoo dyes.
The exhibit was pretty fun (I mean, for nerds): a building with signs and displays of preserved/harvested plants and their uses, and a detailed walking tour around the rest of the botanical garden to find live plants we'd just read about.
We spent a solid couple hours doing it. It was good stuff. Many of the plant dyes are found in the roots, so there wasn't always something interesting to see, but we had many moments of revelation about plants including papyrus, flax, agave (turns out the leaves are great for making soap), cochineal, and more.
Unbeknownst to us, the botanical garden also has a section of its herb garden dedicated to herbs used for beer, wine, and liquor. The included the obvious ones such as hops, grapes, and wormwood, but also a lot of flavoring herbs like lemon balm and chocolate mint.
So, short story short: Check out the temporary exhibit if you have time in the next week, and now you have even more reason to see the whole gardens than you already did.