Question: Ten years ago, I planted some apple seeds and kept one plant that has since grown on to become an attractive tree. This year it bloomed for the first time and it was just beautiful, with hundreds of white flowers. Unfortunately, its apples haven’t grown at all since mid-summer. They’re very small and aren’t attractive, being covered with brown marks. What treatment do I need to give to my tree to get better apples?
Answer: The size of an apple is largely controlled by its genes, as are its flavor, texture, color and disease resistance, among other traits. When you plant apple seeds, the seedlings not only inherit genes from the original variety, but also the parent that contributed the pollen. (Cross-pollination is obligatory for most apples.) Not only that, but this crossing recombines the traits of both parents and can reveal genes, likely recessive traits, not noted in either parent.
This is a bit like the fact that our own children share the mixed characteristics of both parents and sometimes that includes features that haven’t been seen for generations, like a genetic disorder. Your apple tree has a complex and unpredictable genetic background and there is very little you can do to improve its fruit.
Fruit size, for example, is inherited and does not depend (or depends only very little) on any treatment you give the tree such as pruning or fertilizer. It could well be that the “father” of your apple tree (the tree that contributed the pollen) was a crabapple, which is after only only an apple tree with small fruit (apples and crabapples belong to the same species, Malus domestica), and that it transmitted the “small fruit” trait you saw in your apples.
As for the fact that apples “aren’t attractive”, this can be caused by any number of apple diseases such as scab or by insects like apple maggot. Again, apples can inherit good resistance to some or most diseases and insects or can be genetically presdisposed to either or both. There are pesticide treatments you could use to try and prevent both diseases and insects, but if the fruits are going to remain small (and who knows about their taste and texture!), is all that spraying even worthwhile?
In this roll of the genetic dice that is the multiplication of apples by seed, I’m afraid you didn’t win big!
If the fruits are not really going to be edible, rather than wasting 10 years of effort growing the tree for nothing, there’s another possible solution: graft an apple with known characteristics onto your tree’s branches. In fact, you could graft several varieties of “good apples” onto your tree and get a variety of fruits! Apples produced on grafted branches will give fruits true to type to the graft’s donor.
Not Just Apples
Note that very few temperate-climate fruit trees even come close to growing true to type from seed. So if you want to grow cherries, plums, pears, etc. from scratch, it’s best to multiply them by grafting or cuttings.
Of course, if you want to experiment with producing fruit trees from seed, grow not one tree, but hundreds or even thousands. That way your chances of winning the jackpot with a truly worthwhile variety will be much, much better.