Bark cracking. Many magnolias are thin-barked and therefore are considered
susceptible to bark cracking. In particular, yellow-flowered magnolias can be
prone to bark cracking at the base of the trunk. Excess nitrogen fertilizer or
warm temperatures late into the fall season can extend active plant growth.
Consequently, the base of the trunk may not sufficiently harden before cold
weather and freezing temperatures may result in bark cracking .Cracked bark usually becomes
evident in the spring, but may occur due to freezing conditions anytime from
late fall to early spring.
Bark cracking can be avoided by ending liquid or
soluble dry fertilization programs early enough to prevent growth. Use of controlled-release
fertilizers is generally not a problem because most of these products release
substantially less nitrogen during cold temperatures. Other management tools
include reducing irrigation frequency and volume towards the end of the
growing season to slow plant growth and allow them to adapt to cold
temperatures. However, allowing the root zones of evergreen magnolias to become
too dry during late fall and winter can lead to winter burn.
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