Hazelnuts once established are easy to care for. They are require some cold chill and frosts as long as not too late into spring. They don’t mind wet feet during winter when they are dormant but prefer free draining soil through the rest of the year. Though young trees can’t be left in water logged soil for long.
Small trees need protection from wallabies, rabbits and stray cows. This could be with a fence, tree guard or plastic wrap. They are sometimes used as a fodder crop for cattle so it is unwise to try to graze underneath them. When fully mature the trees will block sunlight to the ground and limit grass growth. Like any tree crop they will appreciate mulching and some fertilisation in spring and after harvest. Grass around the trees should be kept low and especially before harvest (maintain in Februrary) so that the nuts can be easily picked up (in March).
You can either leave them to grow naturally (no pruning or desuckering) and they will form a bush up to around 6m tall after 8 years. The nuts will sometimes get stuck in the bush which can make harvesting difficult but hazelnuts can also be used to form a nice hedge when left to grow naturally. The alternative is to trim back all suckers as they appear each year and prune to a single stem (or a couple of stems). This allows for greater access under the hazelnut for harvesting and a more tree like form. Essential if you are going to mechanically harvest.