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One of the most glorious aspects of fall is bringing in the apple harvest.  Every year around harvest time I wonder when exactly to pick my apples, which raises some questions.  What does the apple maturity chart say for this variety? Has the weather this year impacted fruit quality?  They taste pretty good, but are they still too small?  Taste is one of the best indicators, but there are several other signs you can observe to help solve the puzzle.

Apples approaching ripeness go through a period of rapid cell growth, often resulting in daily growth of up to one percent.  Interestingly, the actual number of cells within an apples does not increase significantly after the fruit reaches about ½” in size.  Beyond that point, increases in fruit size results exclusively from growth of those cells.  This rapid cell growth results in changes to the interior and exterior of the apple that are observable and can be used to determine ripeness.

One good exterior indicator of apple ripeness is the base skin color (fruit growers call it ground color).  This is the greenish color that pervades as the apples first form in spring. Simply put, the part of the fruit not facing the sun.  Over the course of the growing season, red or other exterior colors may begin to dominate the skin, but the base color is still visible on areas of the apple surface, especially the shaded side of the fruit.  This base color will progress from a darker green, to a lighter green to yellow.  Once yellow, that is a clue that the fruit is ripe.   

The ease of pulling a fruit from the tree is another exterior sign of ripeness. When an apple is ripe, the stem will break freely from the twig or spur (some apple varieties are non-spur type) on which it hangs when it is pulled and/or slightly twisted.  If much force is needed to get the fruit off the stem, then your apples are not quite ready.

Apples also provide several signs for ripeness internally, besides taste.  The flesh of apple will turn from a greenish color earlier in the season to a creamy white color.  I usually start with taste test and take a look at the area I just sampled.  If the flesh still seems green in color and the taste is not quite sweet enough, it may need some more ripening time. 

However, if taste and color both seem to be right, the seeds can be another indicator of ripeness.  Slice the apple in half to observe the contents of the core.  The seeds color should be brown to dark brown if the apple is ripe. 

Weather throughout the year also plays an important role in apple ripening.  Recently, I had a conversation with University of Illinois, College of ACES Associate Professor, Dr. Mosbah Kushad, to understand how this year’s weather has impacted the apple crop. “This year has been really great on all varieties,” said Dr. Kushad.  “Overall, we have not had all of the problems of previous years and disease pressure has been low.” 

We discussed the recent cooler temperatures and their impact on the rapidly growing apples this time of year.  Dr. Kushad commented, “Fruits are really well colored this year, like a painted picture.  Our nice cooler weather in recent days has added to the richness of the color.  In addition, fruits may be a bit sweeter this year.”  He further explained that cooler weather causes a higher concentration of sugars within the apple, resulting in greater sweetness.  However, the cooler weather this fall has not significantly impacted the timing of peak ripeness.  Dr. Kushad added, “The ‘Gold Rush’ variety typically matures in the first week of October and it appears to be right on track this year, more or less, maybe a few days difference from past years.”

Whether you are a home orchardist or looking for a “U-pick” experience at one of our fine local orchards, now is the time to enjoy the outdoors.  With this beautiful fall weather we are having, it’s the perfect time to enjoy tree-ripened apple fruits grown in Illinois.

 

Ryan Pankau is Horticulture Extension Educator with University of Illinois Extension serving Champaign, Ford, Iroquois, and Vermilion Counties.