I know that shrubs and fruit trees need pruning regularly to help them fruit or flower better, but does the same rule apply to trees?
No, fortunately most trees do not require regular or formal pruning. They grow naturally into attractive shapes, provided they have the room to do so, so it is most important when choosing trees to find out their ultimate height and spread. If they have to be cut to fit, so to speak, it will be difficult, unsightly, and bad for the tree. While they are still young a little help in shaping can be given, and any dead or diseased growth removed.
In a recent thunderstorm one of the poplar trees in our garden was struck by lightning, and a very large branch broke off. How can I deal with the resultant massive wound?
Poplars being large forest-type trees, it would be advisable to call in a professional tree surgeon to repair the damage and treat the tree to prevent rot setting in. It is dangerous for an amateur to attempt such work; but if it is not done, the whole tree could become rotten and ultimately fall.
What is the difference between pollarding and lopping a tree?
Strictly speaking, pollarding is the cutting back of a tree to leave only the main trunk, whereas lopping involves cutting the main branches back to within a few feet of the trunk. In other words, lopping is not so drastic, but both procedures result in a forest of small shoots arising at some point on the tree, and are ways of reducing its height considerably without having to remove it. Willows are pollarded to produce shoots used to make baskets and hurdles.