In the unfortunate event that your previously healthy tree begins to struggle even as late as the third growing season, the likely cause is that it was planted too deep or has a soil nutrient deficiency. This is a potentially serious problem that requires immediate attention. Trees should never be planted deeper than the original soil level-even ½" over is too deep. Take your spade and carefully check, dig down to see if there is any excess soil on top of the original roots. This should be relatively easy to check, as the roots were usually covered in a wire net which should not be totally rotten, but be careful not to damage the trunk. If there is excess soil on top, examine the trunk to see if it has rotten or shows. Trunks should always be exposed to the air, otherwise moisture builds up and rots the bark and cambium. The result is usually tree death, occurring anywhere from six months to five years after planting. Timely removal of excess soil build-up may save your tree, but monitor it closely for signs of decay.
Otherwise, it may be a simple fertiliser deficiency. You can begin by applying a general purpose top-dressing as mentioned earlier. However, if the tree does not show a quick improvement, we would strongly recommend you consider having the soil tested. By all means call us to discuss your tree and seek our advice, but inexpensive soil test kits are available at most garden centres. More sophisticated soil testing is offered by professional organisations. A Google search 'soil testing uk' should bring up a local provider.