I've only ever been to the botanical garden for Glow in the winter. It used to be a really cool event with tons of extremely impressive gingerbread houses on display but not so much anymore.
I've gone to it fine years in a row now. The first two were really good, but it's been going downhill every since. I won't be going back again. It's not worth paying $16 plus parking to see a few mediocre gingerbread houses. There isn't a whole lot inside -- just a small conservatory which isn't really decorated for Christmas.
I have heard the garden is quite pretty outside in the spring and summer so I may try to come back at a different time to check it out.