This place is a macro photographer/plant lover's paradise. It had been a number of years since I was last the the USBG. It had closed a few years back for a much needed renovation. In the process of the renovation, they added an outdoor garden.
On my recent visit there, I was treated to an upcoming exhibit of DC and international landmarks made out of botanical elements. It officially opens at or around Thanksgiving Day and runs thru January 2nd, 2011. A wonderful Holiday treat for young and old alike.
A few tips based on my recent visit... BIG thing... dress in layers. Botanical gardens are basically lavish greenhouses. So being able to shed layers of clothing and have a spot for them is a good thing. Next is that tripods and monopods are not allowed - unless you get a permit. Plan on going back at different times of year, and different times of day - DUH! As any macro photographer will tell you. The other tip is to allow your gear to get used to the temperature differences. Sometimes a simple micro-fiber cloth across the filter will be enough - unless you are coming in from the cruel November temps we have been having of late.
Otherwise take lots of pictures...