April
2005
By
B. Rosie Lerner
Extension Consumer Horticulturist
Purdue University
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Gardeners Fret Over Freeze
Much of Indiana experienced freezing temperatures this week, causing
concern among backyard gardeners. Though there's not much we can do about
the weather, many gardeners wonder if something can be done to help their
plants recover and protect them from future frosts.
Most gardeners are concerned with newly planted flowers and vegetables.
Cool-season plants, such as broccoli, cabbage, peas, potatoes and pansies,
should be just fine. Frost-tender vegetables and bedding flowers, such
as tomatoes, peppers, petunias and marigolds, can be covered with straw
or with tents made of fabric to give a few degrees worth of protection.
This is often just enough to get them through. Some support to keep the
weight of the fabric up off the plants would be helpful in preventing
physical breakage of the tender stems.
Tender garden plants that have already experienced damage from cold temperatures
will likely outgrow it, depending on the severity. Plants that have freeze
damage will initially appear water-soaked but then quickly appear more
scorched, as the plant cells lose their liquid content. Often, only portions
of a plant will be affected, and those stems and leaves can be snipped
back and, in many cases, the growing point of the plant will survive and
produce new foliage.
The biggest concern right now would be strawberry plants. Many cultivars
are currently in bloom and 30 F is the critical temperature that can cause
considerable damage to the flowers. For those strawberry gardeners who
didn't get their plants covered, damaged foliage will be replaced, but
there may not be much of a strawberry crop this year.
Trees and large shrubs are much more difficult to cover for frost protection,
but, fortunately, the temperatures experienced this week were above the
critical injury point for most fruit and landscape trees at this stage
of their development. Most fruit trees are at or beyond petal-fall throughout
much of Indiana. Temperatures would have to dip down to 28 F or lower
to cause much concern after petal fall.
Freezing temperatures can damage newly expanding foliage on landscape
plants, causing leaves to appear tattered later as they mature. There
is a good article about freeze injury to landscape plants at the Purdue
Plant and Pest Diagnostic Lab “Picture of the Week” Web site,
http://www.ppdl.purdue.edu/ppdl/weeklypics/Weekly_Picture6-25-01-1.html.
5 -5-05
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