Tokyo Imperial East Gardens in December

Hi, I understand that December is usually either winter or close to winter, so I'm wondering if there's any sense to go there. I am bringing a first-timer friend along to Tokyo around the early-mid December period.

Early December is usually very good timing for the autumn colors. Depending on the year, teh colors may be nice into mid December. Here is a Tokyo autumn color report from December 1 2012 which includes a visit to the East Gardens:
http://www.japan-guide.com/blog/koyo12/121201.html

Towards late December, the vegetation in the garden becomes increasingly barren, but the gardens can still be a nice break from the city. There may be scattered cherry trees here and there that bloom in winter, but they are nowhere as spectacular as the cherry trees that bloom in spring.

Make sure to visit it when it is open!
The East Gardens of the Imperial Palace is usually closed on Mondays and Fridays. It is expected to be closed on 1, 5, 8, 12, 15, 19, 22, 23, 26 and 28 - 31 of December 2014.