Mulching in winter is important to protect plant roots, soil and microbes from cold weather. The Top 3 tips to mulch successfully in winter is to use bark chips for large, open areas, lay mulch before rain and lay it a maximum of 3 inches thick to allow rain to penetrate through.
Top 3 tips for winter mulching
1. Winter mulch should be laid a maximum of 3 inches
The extra water around in winter means the maximum depth for mulch should always be kept under 3 inches. Mold and fungus including mushrooms and toadstools can grow quickly in winter.
To avoid this, keep mulch to 3 inches to allow the rain to penetrate through to the soil.
2. Use bark chips for open areas
Bark chips and tree mulch are the best mulch types to avoid mold and fungus growth. I have found that sugar cane mulch in winter will grow mold quicker.
Tree mulch forms the perfect mix of green and brown materials which will break down over a 6 month period improving the soil and protecting it from frosts and snow.
3. Lay mulch before rain
If you already have mulch delivered I would get it on the soil before it rains as wet mulch can be heavy, sticky and difficult to move.
Rain will still reach the soil through the mulch and the water will help to hold the mulch in place.
Best mulch for winter
The best mulch for winter is a bark mulch or mixed tree mulch as it will allow water to flow through easily and is less likely to grow mold. Use bark mulch under citrus trees, perennial flowers and shrubs and Mediterranean herbs like oregano, sage, thyme and rosemary.
The best mulch for vegetable gardens over winter is straw, hay or sugar cane. It is best to lay this thinner, around 2 inches to let water flow through.
Straw will protect vegetable roots from cold weather, insulating the soil and protecting soil bacteria.
Use straw around broccoli, peas, cabbage, kale and spinach over winter to protect them through the cold weather.
How to mulch before winter
Mulching before winter is the perfect way to protect and prepare your soil for winter vegetables, protect perennial shrubs and citrus trees.
Before adding new mulch under citrus trees, rake back the old mulch and add a 1-2 inch layer of compost.
Lay a thick layer of bark or mixed tree mulch 2-3 inches thick over the compost under the citrus tree leaf canopy. Old mulch can be used and extra, fresh mulch can be used to fill any gaps.
Mulch your vegetable garden with sugar cane or straw mulch 2 inches thick. After you remove your summer crops like tomatoes and lettuce extra compost and pelleted chicken manure can be mixed into the soil.
Old, broken down straw mulch can also be mixed into the soil to break down 4 weeks before planting winter crops. Top the soil with the new mulch to protect the soil microbes and to hold it in place until you are ready to plant.
Clear the mulch over a small area and plant your winter seedlings into the space.
Cover soil with bark mulch to protect it and keep weed away until you are ready to plant your annuals. If you are preparing a new garden space, plant annuals such as my favorites, the viola and then surround with bark mulch.
Water the flower and mulch in to settle the soil and hold the mulch in place.
What to put down before mulching in Winter
Before you mulch in winter, add a 1-2 inch layer of compost or a thin layer of aged cow manure. This will feed the plants, soil microbes and worms and help to improve soil over time.
Both compost and aged cow manure add extra organic matter to your soil which can help to allow extra rain to drain through in the winter months.
Problems with mulch in winter
One of the most common problems with mulch in winter is mold and fungus growth. When lots of water sits on top of mulch, it can encourage spores to grow in your garden into a range of mold and fungus types including mushrooms.
Mold is not a big problem and will not damage your plants if you use a rake to break it up. For a full description on dealing with mold and fungus in mulch check out my previous article here.
How to store mulch over the Winter
If you have excess mulch made from trees on your property or extra that you have had delivered it can be left in a pile out in an open area. Tree mulch will naturally break down over time which is a great thing.
If you have a sheltered area or open shed space, bark mulch can be stored as long as there is plenty of air movement. Large mulch piles can heat up quickly so they will need lots of air movement.
Protecting mulch from the weather will help to keep the fresh color but allowing it to break down will improve your soil.
How to mulch trees for Winter
Trees can be mulched using bark mulch placed around the tree root zone. This is the area under the tree canopy at least to the edge of the outmost leaves. Place the mulch 2-3 inches thick to protect the tree roots and stop weeds.
Old mulch can be topped up with new mulch and does not need to be removed before adding new mulch to the top.
Leaves as mulch over Winter
Fall leaves can be used as mulch over winter and work best if they are shredded first. Mow over fall leaves to shred them or use a leaf blower with a shredding attachment.
Shredded leaves make a great mulch for large trees and shrubs and will break down quickly once shredded adding extra organic matter to the soil.
Mulching in Winter – Summary
Mulching is important in winter to protect tree roots and the soil bacteria. Mulch can insulate the soil and regulate the temperature stopping it from dropping so low and damaging plant roots or killing soil microbes.
Mulch in winter to protect your plants and help to set your garden up for a healthy spring boost.