Winter mulch

>> Wednesday, October 24, 2007

Here’s what I discovered in reading about mulching for winter.

What is the difference between summer mulch and winter mulch anyway? I mean, you mulch to protect your plants, right? Something I never considered was timing. I was just going to throw a couple of inches of mulch on everything before it snows, much as we throw on a blanket on cold winter nights to keep us warm. Well imagine my surprise when a neighbor told me to wait until the ground freezes before mulching. I must have looked at him as if he were crazy or just pulling my leg. I told him that it would be too late then, that the tender roots of my newly planted plants would freeze to death by then.

So, I went to the internet to do some research. Not that I doubted what he told me. Well, alright, I did doubt him. After being told I should cut my Butterfly bushes to the ground in the spring so they will come back more beautiful and fuller than ever and that action led to their deaths, I decided for my own peace of mind that I’m going to have to double-check everything I hear.

What I found really made sense. The time to apply mulch is after the temperature is consistently below freezing. That’s right, wait until the ground freezes and then apply the mulch. This is because the plant needs to be dormant and winter mulch allows the plant to remain dormant until the spring sun can warm it up again. If you apply it too soon then you create a layer of warmth that could cause the plant to produce new growth and if this happens then the tender new buds will be killed when it does freeze.

Also, by applying mulch before the ground freezes you can smother a plant that is still growing. Because it is still growing and needs air circulation you are actually creating a perfect environment for diseases. So, wait until the ground freezes before mulching.

Typically, 2”-4” is adequate. Organic material, such as stiff leaves, straw, pine needles, hay or bark chips, is best because of two reasons. One, is that this bulky stuff allows some air circulation, whereas anything that mashes down creates a soggy mess that completely seals the plant which leads to, again, that perfect environment for diseases.

Now when I say stiff leaves, what I mean is Oak or Beech because they won’t mat down. Softer leaves such as Maple pack down and blocks air and water from passing through.

Okay, the second reason to use organic materials, as opposed to inorganic, is because it will break down into the soil, while inorganic materials won’t. The reason this is beneficial is because it will allow the soil to become more coarse which facilitates the flow of air and water and prevents clay soil, like I have here in Utah, from packing down into a brick.

Another thing I didn’t consider is the soil needs to be protected from the freeze/thaw cycle that can cause damage by heaving. So again, it makes sense to wait until the soil freezes and then the mulch to keep it frozen. Heaving pushes plant roots up out of the ground and is most harmful to shallow-rooted plants and any newly planted specimens that have not yet rooted.

For roses, it is best to mulch after the first hard frost by mounding soil over the crown, usually 6” deep. This is especially important for grafted roses. As I learned the hard way, a grafted rose is a rose of a specialty color that has been grafted onto a root stock, usually a red rose because they are most common. If the rose dies back to the ground and the root survives you will be greeted with a very different rose than the beautiful yellow or white rose you had last year.

Just as a side note, own-root roses do not suffer this problem.

Remove winter mulch in spring as soon as new growth begins. Pull it away from the base of the plant by about 3” to allow air circulation.

Now that was an especially informative trip to the internet and I told my neighbor he was absolutely right and I will believe whatever he tells me in the future. Well, only after I verify it first.


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