Apple trees seem to last forever without any feed being applied. But, there are good reasons to feed your apple trees each year.
Trees - in their wild habitat - are normally part of a regular recycling of natural organic matter by way of fallen leaves and fruit rotting at the base of the tree, thus being turned into essential food for the tree. Original apple trees (wild crab apples) are no different - growing in hedge rows and other scrubby areas! The 'domestic' apple tree has been bred over many years to give the delicious fruit that we are all happy to eat. One of the main differences being that apple trees are grafted onto special root stocks.
In a garden situation - or even in commercial orchards - the leaf litter and fallen apples are normally removed to prevent the harbouring of certain pests and diseases over the winter. So, its natural source of food is removed.
A balanced feed should be applied early spring - similar to Growmore - or if you wish an organic feed, then Fish Blood and Bone - or just Bonemeal will be ok. Providing you don't mow under your apple tree, then Osmocote type fertiliser - which will release its nutrient over the course of a full season will be good.
There is also a case for feeding in late autumn. The Nitrogen in any food can be absorbed throughout the winter, to build up reserves for new growth in the spring.
A balanced feed will provide nutrients for growth, fruit and flowers, and general health of the tree. It will also offset the effects of regular pruning. Pruning removes vital food from the food chain!
A balance feed is best, simply because it provides the three main ingredients for good growth and health of the tree. You are unlikely to 'overdo' one type of nutrient, which is not always the case if you apply a 'straight' fertiliser such as Sulphate of Potash - recommended in most old gardening books!
An overdose of Sulphate of Potash can result in pale leaves with accented green veins! This is because an overdose feed of Potash, can lock up Magnesium in the soil - making it unavailable for the tree! Don't worry if you have been feeding your apple trees with Potash and overdone it. An application of Magnesium Sulphate - better known as Epsom salt - will do the trick.