Do Apples Need a Frost?                                                                                  CREC ‘Honeycrisp’ harvest (October 1, 2013)

Apples are our largest fruit crop in North Dakota.  They bring pleasure to those growing them and bring many, many questions to University, Extension and CREC personnel.

One of the most commonly held beliefs about apples is that they need a frost to become sweet and ripe.  This is not true.  The warm days and cool nights of fall drive sugar production.  Apples can withstand light frosts but a frost is not needed to complete the ripening process.          

When temperatures fall below 28 degrees, ice crystals can form within the cells.  The amount of damage depends on the temperature and also how long that cold temperature lasts.  If the day is cold and cloudy prior to the freeze event, the fruit will freeze faster than if the day had been warm and sunny. If your apples are frozen on the tree, don’t touch them until they thaw.  These apples will need to be used promptly.

If you feel your apple variety regularly requires a frost to finish, the tree probably has too long of a growing requirement for our climate.  If you eventually replace your tree or add another one, consult nurseries specializing in apples – and especially consider the notes on Minnesota apple varieties.

Maturity vs Ripeness:

• A ‘mature’ apple has reached maximum size, has accumulated all of its starches and can ripen if removed from the tree.  It stores the best.
• A ‘ripe’ apple is ready to eat right off the tree.  It does not store as long.

Start looking for your first fruit on the southern side of the tree and in the outer branches. Taste the apples: Mature are slightly starchy and crisp while ripe have the great flavor you are looking for. Look at the background color: the skin on the shaded side of the fruit should turn from green to yellow when mature and with varying shades of red when ripe.  The seeds of mature and ripe fruit will be dark brown. Pick a few fruits: the stem should break free easily when the fruit is lifted and rotated gently.  When fruit starts falling, the apples are ripe and should be harvested immediately.

Sources and Winter Reading:

University of Idaho Extension CIS 1212:  When to Harvest Apples

Cass County Extension:  Fruit Tree Varieties

Anecdotal stories from an experienced apple orchard: Sponsel’s Minnesota Harvest Apple Orchard

More than any one person can know: www.OrangePippin.com

Kathy Wiederholt
Fruit Project Manager