GOSHEN, Ind. — On October 16, we experienced our first hard freeze of the fall, signaling an end to the growing season for many tender annuals in the area. Plant cells are filled with water. When that water freezes, tiny shards of ice pierce the cells, ruining the tissues. Whether that cold air actually damaged plants in your garden will depend on the species of plant, whether it is in a sheltered spot in your yard, how long the low temperature lasts and many other factors. Plants that evolved in tropical regions may be blackened and wilted by just a couple of hours below 32 degrees, while hardier plants from colder places are unfazed. Your begonias and impatiens may be killed on a night when your spinach is fine.
A hard frost doesn’t mean all plants are done for the year. It’s important to remember that the soil doesn’t freeze as quickly as the air. Even after your plants have died back to the ground, the soil may be warm enough, so the roots are still growing. The soil temperature is often still in the low 40s in mid-November in our region. That is why fall fertilization of your lawn is so beneficial; the turf roots continue to grow well into December and January, filling in dead spots in the lawn even if snow covers the earth.
Trees also have needs after the leaves have fallen. While trees do not need a lot of fertilizer to thrive, they do benefit from watering well into December. Winter winds pull a great deal of water from twigs and limbs, thus the need to keep trees and shrubs hydrated before the ground freezes.
As fall temperatures begin to settle upon us, some people will begin to set their sights on next year’s growing season. The average last 32 degree temperature in our region has been moving back subtly the past few decades. In the 1980’s the average last frost date was May 5-10. Now, the average last frost falls April 21-28 for our county.
— Purdue Extension Elkhart County
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