The daring escalade,
The plunging ships, the bleating sheep,
The happy children ankle-deep
And laughing as they wade:
All these are vanished clean away,
And the old manse is changed to-day;
It wears an altered face
And shields a stranger race.
The river, on from mill to mill,
Flows past our childhood's garden still;
But ah! we children never more
Shall watch it from the water-door!
Below the yew--it still is there--
Our phantom voices haunt the air
As we were still at play,
And I can hear them call and say:
The  yew  is an interesting choice.  It’s a poisonous fruit-bearing tree with bright and tempting red berries. 
 
 It’s traditionally symbolic of death, and can be found in cemeteries.  It’s also one of the most historical English trees, so perhaps it represents both their mortality, and the history the children have been steeped in by virtue of their exposure to the nursery pictures.
To Minnie