Another Cherry Tree Problem

I have lived in my home for 21 years. When it was built I asked the builder to leave a trench for planting along the front drive dividing our house and next door. My green and cabbage days concerning builders/topsoil/rubble etc. Anyhoo I planted three cherry trees. Since that day my neighbours and I have discovered it was solid concrete underneath. The yard from the previous dwelling. He is worse than I as it affects his whole front garden. To cut a long story short. The trees are now 21 plus years old and are nowhere near as big as they should be. There is now an elaeagnus hedge growing there too. It's hard to access the soil in which they are growing. I mean by that I cannot dig it up to replace it etc.
Has anyone any ideas how I can improve their growth by other means?

 

Hi Rhyleysgranny,

A tree's size is determined in part by the roots. The root plate not only acts as a way of absorbing water, air and nutrients from the soil, but also as anchorage, thus holding the tree firmly in place. A tree will not grow beyond the roots' ability to support it, if that makes sense. As the roots can not get much purhcase in the ground due to the concrete underneath, the tree has limited anchorage and nutrient uptake. I'm afraid you're stuck with the trees as they are.

 

Thank you Tree Surfer for your information. I thought that there wasn't much I could do. However they do flower beautifully. I trim the branches to make them a bit bushier. I appreciate your time
xxx