Frost Protection Options

Weather forecasts indicate that gardeners in our area will want to consider frost protection opportunities tonight and tomorrow night, Sept. 17 and 18.  Forecast lows for most of the Marinette County area are projected to reach the freezing mark, indicating that most gardens are at risk for damage.

Plants facing the most risk are the ones which are most temperature sensitive, such as basil and melons.  However, anything in the tomato family, any vine crop, and any beans are also likely to face damage potential.  Protecting these types of plants the next couple nights may extend their growing season for a couple more weeks, giving them the opportunity to ripen properly and increase both yield and quality of the fruits produced on these plants.

Start the process of frost protection by analyzing your garden space.  Ask yourself which plants are worth protecting, and which areas are capable of being protected properly with the materials you have available to you.

You may be better served to harvest melons and basil plants, especially if you know that your location is in a cool pocket.  The reason for this statement is that these plants face damage around 35 degrees, and normal protection methods (tarps, blankets, etc…) usually only provide a few degrees of protection.  The more complete the coverage, with fewer holes, seams, etc… that allow the insulated air to escape, the better frost protection we can achieve.

For other sensitive crops, arranging materials that hold air and act as insulation will likely provide the necessary protection.  The best situation is to be able to have some type of frame or support that keeps the tarps, sheets, or blankets off of the plants themselves.  The tarps usually get down to the air temperature around them, so any plant material touching them is likely to face damage.  The air holding area under the tarp is where it stays warmer and is where you want most of your plant material.

Focus your efforts on the plant types facing damage.  Root crops, cabbage family crops, and crops which are fully mature do not need protection right now.  They can handle colder temperatures without facing damage, or can simply be harvested to prevent cold exposure.  Tomato and pepper plants with a number of immature fruit are probably highest priority, as well as winter squash and pumpkins which have immature fruits.

Later in fall, we can use other methods, such as adding water buckets under the tarps, to give protection to less sensitive plants and keep them alive during even colder nights.   For these two nights right now, we don’t need to use extra methods, but can make our gardens look like supersized patchwork quilts that protect our sensitive crops.

If you have questions about frost protection, harvesting or storage of fruits and vegetables, or any other agricultural or horticultural issue, contact Scott Reuss, Marinette County Agriculture/Horticulture Agent.  He can be reached via e-mail at or through the Marinette office of UW-Madison, Division of Extension, in the courthouse, at 715-732-7510.

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