The (almost really) Complete Works of Lewis Carroll

My First is a berry

Source: letter to Olive, Ruth, and Violet Butler, December 29, 1892

My First is a berry:
My Second is sorrow:
My Third from the cherry
Its sweetness doth borrow:
My Whole is too merry
To care for the morrow!

There is another verse-riddle in this letter:

VIOLET
VIOLET
VIOLET
VIOLET
VIOLET

To find the eldest of the pets.
Go search among the violets!