We are well into the month of October and little by little trees in Nebraska are starting to change color. Bob Henrickson is the Horticulture Program Coordinator for the Nebraska Statewide Arboretum and says we won’t see those true fall colors until the temperature drops.
Henrickson says the best colors happen when the first freeze is mild, about 30 degrees, followed by warm days and cool nights. Those conditions always result in great fall color. Henrickson says, “If our first hard freeze is in the mid-20’s, the first things that color up, often the ash, sumac, the red maples, it will be very muted because that low temperature of 25 degrees or colder that first night will basically knock off the leaves off freeze-dried green rather than setting them in motion for a good fall color with a light freeze.”
Henrickson says this process of shedding leaves is hard work for trees. He says there is a small abscission layer grows between the leaf and the stem. A freeze shuts off the chlorophyll going to the leaves and the result is a change in color.
We are very fortunate in Nebraska that the fall season is a two-parter. Henrickson says, “The early fall season we see some of the trees that color up very early like the red maples, your green ash, your white ash and things like that. There is almost a second season later on in late October, around Halloween time, where your oak trees are coming on and showing their true fall colors so almost a second season in fall.”