Q: I have a producing ‘Granny Smith’ apple tree. This year I have a lot of apples on the tree and want to know when I am supposed to pick them.
A: Since Granny Smith is a green apple, it’s hard to determine ripeness by color. Determining ripeness by taste is the way most people would answer. Granny Smith is a late-maturing apple so start tasting yours sometime in late October.
A scientific method to determine ripeness is to spray an iodine solution onto a cut apple to see how much of the fruit has changed from starch to sugar. Take an ounce of iodine and mix it with 15 ounces of water and put this mixture in a spray bottle. Slice an apple in half horizontally through the seeds. Spray the apple flesh with the iodine mixture. A fully ripe apple will stay white, an unripe apple will turn black. The ideal time to pick is when the inside of the apple is white, the outside edge of the apple is white and there is a small band of black between them.
Another method is to count the numbers of days since full bloom, if you remember when that occurred. Granny Smith is usually ripe at 165 – 180 days after full bloom.