Not long ago, I posted about "pollardize" meaning to severely cut back top growth of trees, in my neighborhood because their root system has been unable to expand sufficiently to maintain the necessary balance between shoot and root, in this area due to predominance of asphalt and houses over turf.
I have just started to re-read Dickens' Great Expectations, and the word "pollard" is used simply to mean a variety of tree. I wonder what the connection is.

I found one site which gave "pollard" as a type of willow in the Netherlands. And a dictionary definition:

Pollard \Pol"lard\, n. [From Poll the head.]
1. A tree having its top cut off at some height above the
ground, that may throw out branches. --Pennant.
2. A clipped coin; also, a counterfeit. [Obs.] --Camden.

3. (Zo["o]l.)
(a) A fish, the chub.
(b) A stag that has cast its antlers.
(c) A hornless animal (cow or sheep).