Harvest & storage
The starch test for picking time
A simple test that shows how far fruit has ripened.
Relevant stages: Fruit Development IV, Pre-Harvest.
As apples ripen, starch turns into sugar. An iodine solution stains starch blue-black, so it shows how ripe the fruit is.
How it is done
- Take a sample of fruit from around the orchard, from different trees.
- Cut each apple across the middle.
- Dip the cut face in the iodine solution for about a minute.
- After a few minutes, look at the stain. More blue-black means more starch, less means riper.
- Compare with a starch chart.
Using the result
- Start testing about four weeks before the expected harvest and repeat weekly.
- Fruit for the fresh market is usually picked a little riper than fruit for long storage, which is picked earlier so it stays firm.
- Every variety has its own target, so ask your agronomist or buyer for the right reading.
- Use it alongside seed colour (brown), ground colour and how easily the fruit comes off the spur.
General guidance. Always read product labels and consult an agronomist for problems specific to your orchard.
