That all depends – there are a number of variables. If they are growing in good, fertile deep soil, and are getting adequate summer moisture through irrigation, then they will grow a lot bigger than trees which are planted in heavy clay soil, with poor drainage, or lack of watering in the summer. At an average, a stone fruit tree in good conditions could reach 3-4 metres. Pears can grow into 5 metre trees, our apples grow to 3 metres, or less depending on pruning, quinces grow to two metres. Dwarf trees will usually grow to two metres or less.