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Preparing Perennials For Winter

By Wayne Jewell

If you have not already done so, now would be a good time to “put your perennial plants to bed” for the winter.  You know, the plants that go dormant over the winter and come back each spring to delight us with their new growth and lovely blooms as opposed to “annuals” which need to be replaced on an annual basis. 

 Under “ideal” circumstances, there is not much that we would need to do for plants that are suited for our north east Ohio climate.

Of course, when I talk about “ideal”, the soil is a nice rich loam, that has received ample fall moisture and blanketed with several inches of snow that remains until Spring when, the soil warms up again to stimulate new growth.

The reality is that in this part of the country, we have freezing temperatures one day and warm temperatures the next along with too much moisture or too little. On top of this, many of our garden soils tend to have a high clay content.

One of the first things that I learned in one of my early soils courses while in college, is that soils with a high clay content, tend to shrink and expand as they freeze and thaw. This is one of the biggest reasons that we lose perennial plants.  It is this “freeze/thaw” cycle that tends to force the plants out of the ground and in so doing tears roots off causing loss of the plant. A deep blanket of snow is actually an insulator against the freeze/thaw…..as long as it remains in place.

My fellow “gardeners” know that before the perennial plants went in, time should have been spent preparing the soil by not only tilling it but by adding any necessary organic matter such as compost, checking the soil pH and nutrient levels  by way of a laboratory soil test and adding fertilizer and lime (or Sulphur) according  to test results. Soil amendments such as compost (which is decomposed plant material) and gypsum help to break up or aggregate a soil that is high in clay.  This improves drainage while retaining enough moisture for plant survival and also makes many of the nutrients that are normally tightly bound in clay more available to plants.

So what if our garden soils have a high clay content and this freezing/thawing that causes plant heaving is a problem-what can we do???

Trim your perennial plants down to within a few inches of the soil and cover them with about 3 inches of shredded mulch.   This layer of mulch will act as an insulator against the freeze/thaw cycle.  Before you add this layer of mulch, you can also add some fully decomposed compost and take some soil samples to send out for analysis. Perennial plants love to receive an annual replenishment of compost so it is never too late to add any to the soil.  Also, soil test labs tend to be less busy in the fall than they are in the spring so it shouldn’t take as long to get your test results back in the mail.  If you choose not to add compost before you put the mulch down, the mulch itself will eventually break down and add to the soil organic matter. It just takes longer to do so.  Leaving a small portion of the plant sticking out above the mulch will aid in locating your perennials in the spring in case you do need to replace them or cut back to new growth. 

Make sure your soil is either watered well, or has received plenty of fall moisture prior to adding a winter blanket of mulch. This will guard against desiccation or moisture loss during the winter.  It is better for plants if the ground freezes with ample moisture rather than being on the dry side.