Yes, some people do prune it so it ends up looking like a lollipop.... or a pudding. But you don't have to do that. If you really want to keep the shrub shorter than its natural 8 to 10 feet, just remove the tallest 3 or 4 stems after they bloom. Don't take away too many as the shrub needs to keep its strength up, but you can usually remove up to a quarter of the bush each year without sending it into an irreversible decline.
Yes, it does spread a bit. The natural shrub, like the natural woman, spreads a bit with age. But you can easily enough dig out the stems that appear around the base of the plant to keep it within limits. It's no worse than lilacs, or some roses.
Yes, if it is a really cold winter, some of the flower buds will freeze. Then only the buds which were protected by snow will bloom, giving your shrub the effect of a bad home perm. The only thing you can do about that is to get the variety 'Ottawa', which is a good deal hardier than the species. Mine has come through this past winter's -28C temperatures with all flower buds intact.
But the best thing about Forsythia? It is just about the earliest and easiest to force flowering shrub we have. If you have a bush, go out right now and clip off some branches, the ones that show an abundance of the pointed brown buds. Just stick them in a glass of water in the window and in a week or so you'll have flowers. Here is a small branch I cut 14 days ago. It's still in great shape after being open for about a week. I warn you, I'm not a flower arranger.... you can do better than this:
There are a couple of other varieties of Forsythia available as well. I have one which is prostrate, fanning itself out along the ground and rooting as it goes. I have it in the rock garden, cascading down a steep slope. Except for its tendency to swallow everything in its path, I wouldn't want to be without it when it blooms in early Spring. The third one I know of is supposed to be a dwarf.... well, it is maybe a little smaller than 'Ottawa'.
Forsythias are great in shrub borders, by the way. A brief burst of glory in early Spring, then a quiet green presence for the rest of the summer. It really ought to come back into fashion!
