Exploring the Benefits of Mulch: Protect Your Garden This Winter

Mulch is often the forgotten element in a garden, especially at the approach of winter. Yet, for some plants, mulching is crucial to ensure their survival. Not all plants require mulching, but for those that do, they will benefit from mulch’s insulative properties, which will shield fragile plants from extreme cold and fluctuating temperatures. The below article explores the various benefits to mulching, and which materials are best for your garden beds during the winter. 

Benefits to Using Mulch in Raised Garden Beds

Mulching assists gardeners in promoting a healthy garden in the long-term. 

• Inhibits weed germination and growth. Your plants aren’t the only things that become dormant in the winter – weed seeds lie in wait until spring, when they suddenly erupt in unsightly patches. Apply a layer of mulch to suppress spring-germinating weeds.  
• Provides vital layer of insulation. Mulch adds a protective layer between the air and the soil. 
• Stabilizes soil temperature. Freeze-thaw cycles can uproot plants with shallow root systems, leaving them exposed to frigid temperatures or pests. Repeated thawing and freezing of the soil will cause water to expand, which will cause plant roots to lift or heave. Mulch can help in maintaining a consistent temperature and preventing the ground from prematurely thawing. Spread mulch over perennials and other plants that may be affected to reduce the issue.
• Maintains soil health. Organic mulches such as grass clippings and leaves improve the structure of the soil by adding organic material back into the soil.  

Materials to Use for Mulch

Though some gardeners use mulches more for perceived ornamental value than their benefits, you’ll want to select mulches that can protect plants from the chill and won’t become compacted under snow. Common winter mulches include straw, bark chips, pine needles, and other coarse-textured materials. Some gardeners also choose to add regenerative compost as an amendment beneath a top layer of mulch. 

• Straw: Straw mulch is a general-purpose option favored by gardeners. It is superior to other mulch. Look for a straw mulch that has been sustainably sourced and offers multiple benefits, including reducing evaporation, maintaining optimal soil temperature, and promoting a thriving microorganism ecosystem. It also adds an aesthetic value that complements the earthliness of vegetable beds. 
• Hay: Contains a similar composition to straw, but may also contain weed seeds.
• Leaves and compost: Leaves, grass clippings, and other organic material repurposed from a fall garden are a good option for bulbs and perennials, as they enrich the soil with organic matter while allowing new growths to poke through during the spring. 
• Pine needles: Although it’s a myth that pine needles acidify the surrounding soil, pine needles remain the mulch of choice in many Southern landscapes, where azaleas, rhododendrons, and other acid-loving plants dominate. Pine needles retain many of the traditional benefits of mulch – insulation, moisture retention, and soil regulation – but keep in mind that they are slow to decompose. 
• Bark chips: Slow to decompose, wood chips are often used as the top layer around trees and shrubs. Avoid fresh wood chips, as it can deplete nitrogen in the soil, and those made from pressure-treated woods. 

Applying Winter Mulch to Your Garden

Winter mulch is usually applied after the first hard frost, which could be as late as November or December in Southern climates. If applied too early, it can actually trap heat within the soil, exacerbating freeze-thaw damage. Avoid mulching during late fall. 

One problem that commonly occurs is over-mulching of trees. Excessive mulch causes a layer of impermeable material to build up, leading to suffocation and death. While 2-4 inches suffices for most mulches, organic mulches only need around 2 inches – any more will suffocate roots and waste money. Finely textured mulches such as shredded hardwood should be applied sparingly compared to mulches with a coarser texture, such as pine bark nuggets.  

Do I Need to Use Mulch?

Not all plants require mulching, but for those that have to endure the onslaught of harsh winters, they’ll need extra help. Deciduous plants, hybrid tea roses, and less-cold hardy plants will often need a layer of mulch to act as a barrier against the elements.  

What are Other Ways to Protect my Plants?

Raised garden beds can reduce soil compaction and greatly mitigate the freeze-thaw cycle that comes with poor draining soil. Row covers and other extensions can also protect your plants from midwinter’s cold. For delicate plants, you can grow and transport them inside in elevated rolling planters. These inventive rolling planters have been equipped with wicking cells that collect and gradually redistribute water to your plants, reducing the need to water as often. 

Winter Mulching Best Practices

• Mulching trees & shrubs: Too often, a pile of mulch is dumped around trees to create a volcano-like mound – a frequent sight in urban landscapes. While the effects of tree death from mulch volcanoes seem exaggerated, this practice can indeed be harmful. The pileup of mulch can leave them vulnerable to structural damage, root stress, and disease. The correct way is to apply 2-3 inches of mulch 6-12 inches away from the base of the tree. Trees planted within the last five years or are not reliably winter hardy need 6-inches deep, which can be reduced to 2-3 inches mid-spring. For shrubs, 3-4 inches away from the shrub's base is recommended. 
• Mulching plants: When mulching plants, leave a mulch-free zone of 1-2 inches . Ornamental grasses and other perennials that provide winter interest can be left alone, while less interesting ones should be pruned and mulched with straw or hay. 
• Roses: Exotic flowers do not last long in severe winters, and roses are no exception. Hybrid tea, grandiflora, floribunda and other modern roses are not considered winter hardy and require extra winter protection. In the coldest of winters, when temperatures plunge to sub-zero, it is crucial to protect the vulnerable graft unions.