Spring Season Freeze Information and Plant Vulnerability

 The record breaking warmth experienced over the second half of March has enabled an early start to Spring over much of the Midwest and Ohio Valley, including central Indiana. With many flowers and plants already well in bloom, here is important information about average dates for the last occurrence of freezing conditions.

Spring Final Freeze, Average 32 degree date map Spring Average Final Freeze Dates, 28 degrees
Average Date of Last 32 Temperature in Spring Average last date of 28 degree temperature in Spring

 

Above are maps of the dates of the average final 32 degree and 28 degree temperatures of the Spring. Maps are courtesy of the Midwest Regional Climate Center. Click the maps for a larger version.

Here is some information on the final spring freeze (32 degrees), including its average date of occurrence, and the earliest and latest dates in the spring that the final freeze has happened. All data is from Co-op and ASOS observations.

 

Location
Average Last Date
Latest Date
Earliest Date
Records Back to
Freelandville
April 11
May 10, 1966
March 22, 2005
1929
Washington
April 13
May 20, 1897
March 20, 1925
1897
Bloomington
April 14
May 27, 1961
March 25, 1998
1896
Crane Naval Depot
April 14
May 11, 1947
March 22, 1967
1942
Indianapolis
April 17
May 27, 1961
March 24, 1998
1871
Columbus
April 18
May 27, 1965
March 25, 2005
1894
Greencastle
April 20
May 25, 1925
March 25, 1998
1896
Seymour
April 20
May 27, 1961
March 23, 1895
1893
Greenfield
April 21
May 27, 1961
March 30, 1999
1904
Greensburg
April 21
May 27, 1961
March 28, 1999
1898
Terre Haute
April 21
May 27, 1961
March 27, 1999
1954
Rockville
April 22
May 25, 1925
March 27, 1999
1893
Rushville
April 22
June 1, 1966
March 31, 1999
1901
Shelbyville
April 23
May 27, 1961
March 30, 1999
1898
Winchester Airpt
April 24
May 27, 1961
March 30, 1999
1943
Muncie
April 25
May 19, 2002
March 28, 1999
1965
Shoals
April 25
May 28, 1961
March 27, 1913
1913
Anderson
April 25
May 27, 1961
March 23, 1981
1895
Whitestown
April 25
May 30, 1947
April 3, 1965
1901
Newcastle
April 26
May 27, 1961
March 31, 1999
1950
Frankfort
April 26
May 27, 1961
March 30, 1999
1914
Elwood
April 27
May 27, 1961
March 31, 1999
1948
Delphi
April 27
May 30, 1961
March 30, 1999
1893
Kokomo
April 28
May 27, 1915
April 2, 1941
1901
Martinsville
April 28
May 27, 1961
March 29, 1959
1950
Spencer
April 29
May 27, 1961
April 4, 1965
1949
West Lafayette
April 30
May 27, 1961
March 30, 1941
1901
Farmland
April 30
May 25, 1925
April 5, 1915
1893

For frost/freeze data for sites from all sections of Indiana, please download the pdf table from the National Climatic Data Center.

For frost data for hundreds of locations nationwide, visit:

http://www.ncdc.noaa.gov/oa/climate/freezefrost/frostfreemaps.html

 

 

Plant Vulnerability to Frost/Freeze Conditions across central Indiana (as of March 22)

Courtesy of Rosie Lerner, Extension Consumer Horticulture Specialist and Master Gardner State Coordinator, Purdue University

Following a particularly mild winter but cold enough to easily satisfy the chilling requirements for flowering, our spring blooming plants have had a tremendously early and spectacular display this year. Blooms are about 4 -6 weeks ahead of “normal” this year and bud counts are high. Average temperatures across Indiana have been more like late April to early May than mid March. Due to the recent stretch of record warmth, it’s a bit like the grand finale of a fireworks display. While the sequence of bloom appears to be staying in order, it’s as if the season is on fast forward bringing nearly everything into bloom all together. Our current cast of characters (March 22) in West Lafayette includes forsythia, daffodil, magnolia, redbud, flowering dogwood, ornamental pear, cherry, peach, plum, tulip, serviceberry, Korean spice viburnum, and crabapple to name a few. Similar blooms and flowering have been seen across all of central Indiana.

For plants whose primary ornamental feature is flowers, you’ve enjoyed the show thus far and barring any really unusual weather events, the plant itself will not be killed by frost/freeze. However, there certainly could be injury to foliage and young twigs, likewise for herbaceous perennials and hardy annuals. Except for conifers, plants that lose leaves or leaf buds will produce new ones. If buds are injured, but not killed, new leaves may be cupped, crinkled, twisted, curled, wilted or tattered. Though unsightly, most plants will eventually outgrow this type of injury. The Purdue Plant and Pest Diagnostic Laboratory (PPDL) has some good articles showing freeze injury from previous years. www.ppdl.purdue.edu/ppdl/hot10/5-14.html and www.ppdl.purdue.edu/ppdl/weeklypics/Weekly_Picture6-25-01-1.html.

With regard to fruit crops, fruit set and development is susceptible to injury when temperatures drop to near or below freezing. The degree of susceptibility depends on several factors, most notably species, stage of development, and temperature (specific temp as well as duration of exposure.)  At petal fall and fruit set, apples, peach, and tart cherry can be expected to have 10% bud kill at 28ºF, but 90% bud kill at 25ºF. Pears are quite similar with 90% bud kill at 24ºF.  More information on fruit bud hardiness can be found from Michigan State University at http://www.hrt.msu.edu/faculty/langg/Fruit_Bud_Hardiness.html.

Strawberries and grapes are even more sensitive; critical temperature is 30ºF for strawberries. Grapes are a bit more complicated but suffice it to say that once the leaves begin to expand, 28ºF is likely to cause significant reduction in fruit set. More information on Frost/Freeze and impacts on plants can be found at http://www.ces.purdue.edu/extmedia/ho/ho-203.html .

What can home growers do if frost is predicted? Small fruit plants can be covered to provide a few degrees of protection temporarily. Blankets, throws, and tarps can be used but provide stakes, wires, or other supports to keep the weight of the cover off of the plants. Straw would be useful for covering low growing plants such as strawberries and herbaceous perennials. Covers need to be removed as soon as possible after the threat is past to avoid over-heating and over-shading. It is impractical to do much for trees, large shrubs, and large garden areas.

Additional information on horticulture can be found at http://www.hort.purdue.edu/ext/conhort.html.

 

 

Prepared by the Indianapolis NWS Climate Services Team and Rosie Lerner, Purdue University

 



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