Why, When and How to Mulch. And what is the difference between a Summer Mulch and a Winter Mulch?
Summer mulching and winter mulching have completely different purposes and the mulch you should use is also different. Understanding the purpose and benefit of each will help you to understand when and how to mulch.
Benefits of Summer Mulch
Summer mulch gives your landscape a finished look
Helps the soil to hold moisture
Helps to control weeds by smothering young plants and preventing air and sunshine from germinating seeds
Helps prevent extreme temperature fluctuations, keeping the roots consistently cool in hot periods and warm in cool periods
Many mulch materials can add nutrients to your soil as is decomposes
The first thing you need to do is select an appropriate mulch. Much more than personal preference is important, so consider the benefits of the many types of mulch available. For a new bed, generally 2 to 4 inches of mulch should be applied over the entire bed. But if your beds are already mulched, you may not want to just add mulch over the existing mulch. If the existing mulch as become densely matted it creates a barrier that moisture and nutrients has a hard time penetrating. I just rake mine up to loosen it and sometimes just move it to the back of the bed. When I put down the new mulch that area just needs a visually refreshing layer. Generally the entire bed can be topped off two or three years before it becomes matted. In any case, never allow the mulch to become so thick that is smothers your soil.
Summer Mulching Tips:
Mulch should not directly contact plants. Allow a few inches around annuals and perennials to allow room to grow. New shrubs and trees should have a layer an inch or two deep of mulch near, but not touching the trunk. An outer ring of deeper mulch will help retain moisture in the drip line and hold moisture within the ring.
Matured trees should have a small mulch ring to prevent damaging the trunk with lawn mowers or weed whips.
The best summer mulch is a living mulch. Using spreading ground cover and low growing perennials accomplishes all the benefits of mulch without the expense and reapplication. As your ground covers grow and spread you will have less and less open area to mulch.
Rock is NOT mulch and neither is weed fabric and plastic! The use, purpose and benefit of rock and fabric is much different.
Winter mulch has a much different purpose than summer mulch, so recommended mulching materials are better suited to the need. The objective is to keep frozen soil frozen, not keep it warm. This keeps your plants dormant for the winter.
Benefits of Winter Mulching:
Winter mulch provides an insulating blanket that helps prevent the soil temperature from fluctuating dramatically. Warm spells mid winter can allow growth to begin, only to be killed again once the temperatures drop. This constant stress will damage if not kill the plants.
Young plants not well established will give some protection from extreme cold. This is especially beneficial if you have selected marginally hardy plants.
Winter mulch will help prevent fluctuating soil temperatures from heaving plants right out of the ground.
Winter Mulching Tips:
Use loosely piled material such as straw (not hay, as it usually contains weed seeds), coarse bark or large wood chips that will allow air flow and insulating air pockets. Fine materials such as grass and soft leaves will compact and smother or rot plants. Oak leaves can be used for roses and perennials. Shredded oak leaves work well around shrubs and trees.
Not everything needs to be winter mulched. Marginally hardy perennials, young perennials, shrubs and trees, roses and shallow rooted plants should be mulched for winter protection.
Do not mulch until the ground freezes. Remember that the purpose is to KEEP the soil frozen and the plants dormant.
Completely cover perennials and roses that require winter protection. Young trees and shrubs should be mulched as noted for summer mulching.
Wait to remove winter mulch until the soil has warmed and you begin to see budding or growth. Removing the mulch too early exposes the tender new growth to potential frost.
My best advice then about summer mulching? Buy more plants! Preferably ones that don’t require winter protection.