we have about 12 trees tallest around 15ft, separating property line between us and neighbor. they then around 2 yrs ago put up a large white fence against trees on their property line. Can we top the trees so the don't get so tall so fast and make them grow wider? , and when would be the best time of year to do that, and can be trim branches that will hit the fence.
If you cut more than a little bit off they may not be able to sprout replacement shoots, restore and maintain a green covering on top. To be grown as a pruned hedge they should have been getting trimmed every year since a few years after planting, developed and maintained as a hedge up to this time. Like most other conifers these consist of a shell of green growth covering a mostly bare interior, cutting back into the bare wood inside is likely to result in a dead, bare stub or stump that does not refurnish itself.
Norway’s are large, fast growing trees. In addition, they take well to shearing, that’s why they are commonly grown as Christmas trees. On the other hand, if allowed to grow naturally they can be very stately in appearance, provided they are given the proper space and growing conditions. The biggest mistake people make when planting Norway’s is not giving them enough space. I recommend giving them time. Prune the branches back that hit the fence and let the rest go. That fence will soon disappear. What ever you do don’t cut the top of the tree off, if you must prune follow Ron and and Michael’s advice
