If you have a garden, one of the first things you should put down is mulch. Versatile groundcovers not only suppress weeds, reduce soil erosion, control dust, and keep your garden from turning into a swamp, but they’re also one of the best and most important ways to restore your soil .
Why else should you use mulch?
To prevent weeds from growing: Seedlings must be covered with a layer of mulch and some seeds will not germinate without light. To keep it moist: Mulch prevents evaporation, so you won’t have to water as often. To retain warmth and regulate soil temperature: Mulch insulates from cold and heat, protects plant roots from the harmful effects of extreme weather, and reduces frost heave (continuous freezing and thawing of water in the ground). This prevents the soil from expanding and contracting. . To protect soil structure: A layer of mulch helps reduce runoff during storms and prevents the soil from forming a hard bread (crust) in hot, dry weather. As a slow-release fertilizer: Many organic mulches release nutrients into the soil as they decompose. Decorative purposes: Mulch can be used to organize beds and create a cohesive look throughout your garden.
But how do you know what to use and where? There are an infinite number of materials called mulch, and the best one depends on your actual usage. (Surprisingly, there are times when you should leave the soil bare. See below for more information.)
Here’s what I’ve learned from personal experience and what I recommend for different types of fields. (See our overview of the best organic mulches to use.)
What kind of mulch should I use?
annual vegetable bed
compost straw autumn leaves mulch mushroom compost black plastic
perennial bed
Wood chips Shredded bark or bark nuggets Wool Pine needles Straw Compost
flower bed
Compost Wood shavings Wood chips Shredded bark or bark nuggets
under shrubs and trees
Wood chips Shredded bark or bark nuggets Pine needles Compost
paths and large areas
Wood chips Shredded bark or bark nuggets Pea gravel Crushed stone Burlap
cold weather garden bed
Straw Fallen leaves Pine needles Clipped grass Plant debris Wool Compost Animal manure
container
wood shavings wood chips compost
living multi
Lettuce Carrots Beetroot Coriander Parsley Creeping Thyme Creeping Oregano Alpine Strawberry Yarrow Chamomile Sweet Alyssum Trailing Nasturtium
Things you should never use
I often see stained wood chips placed in the front gardens of new homes, but this is something I absolutely refuse to do. Sure, that all-black (or red or dark brown) mulch may look smooth at first, but over time it’ll bleed through with artificial color and end up looking terrible. Also, I’m always curious about what’s in the dye…
The same goes for rubber mulch, which is made from recycled shredded tires. While you should be applauded for finding a new use for tires, your garden will end up smelling like a tire shop on a hot day. Also, the potential for leaching (of zinc, aluminum, cadmium, chromium) is very high, so it is unlikely to be a material that will contaminate your garden.
How to apply (and amount)
Start by deciding how much space you need. If you’re shipping mulch from a nursery or landscaper, you can use a mulch calculator like this one to figure out how many bags, cubic feet, or cubic yards to buy. (You can also calculate mulch for oddly shaped beds like triangles or trapezoids.) If you sign up for a service like Chip Drop, trucks can dump large loads on your property. Be sure to reserve space.
Once you have mulch on site, follow a few simple guidelines.
First, remove any weeds in the area. They are tenacious and can get through mulch. When starting seeds, a very thin layer (1/4 inch or less) of a light, fluffy mulch, such as straw or shredded leaves, will keep the soil surface moist until germination. For established plants, spread a 2- to 3-inch layer of mulch on the ground around the plant. Leave some breathing room. Mulch should always be kept a few inches away from the stems and trunks. To prevent matting, especially with dense mulch like fallen leaves, fluff the mulch (with a small rake or your hands) periodically throughout the season.
When to apply mulch?
Most organic mulches last throughout the growing season, so they only need to be reapplied in the spring and fall. If the mulch is starting to get a little sparse (or blown away), be sure to top it up so the soil is always covered with 2 to 3 inches of mulch. (More than that is unnecessary and may even have a negative effect on the plants.)
In autumn (after several frosts), apply a thick layer of mulch to protect the soil from frost heave, protect the canopy and root systems of overwintering plants, and prevent the formation of a crust on the soil surface. As mulch decomposes during the winter, it nourishes the soil and improves its structure.
The exact amount depends on your climate. In warmer regions, you may not need more than 3 inches to survive the winter, but in colder regions, as much as 8 inches is fine (especially for fall-planted garlic, cold-hardy overwintering herbs, or perennial herbs, on vegetables, flowers).
Even if there is nothing in your garden, you should still apply mulch. If possible, avoid leaving the soil bare over the winter. That’s because soil nutrients can be depleted by heavy rain, and mulch works to reduce leaching and surface water runoff and keep soil structure intact.
Is too much mulch bad?
Yes, I said three paragraphs ago that too much mulch can be harmful, but that only applies to actively growing plants that need access to oxygen and water.
In autumn and winter, when perennials are dormant, their root systems must be protected from dry winds and freezing weather. Mulch retains moisture (so plants can stay hydrated even when cold, dry winds blow) and helps the soil protect plants from uprooting during freeze-thaw cycles.
When the weather starts to warm up in late winter or early spring, you can start thinning the mulch to increase air flow to the soil and roots. Which brings me to my final point…
When to leave soil bare
Yes, there are times when you actually want to leave the soil exposed. In the spring (especially if you live in a cold or rainy climate), remove all winter mulch and leave the garden bed uncovered to warm and dry, allowing the soil to thaw and become “workable.” It is necessary to make it so that
Removing mulch also encourages the movement of slugs and other insects that have overwintered in your garden’s flower beds. (Otherwise, they’ll continue to get comfortable in the damp, dark recesses of the mulch and take over all your tender new seedlings.)
Empty garden beds also make it easier to sow seeds. Once the seedlings have grown a few inches (past the delicate seedling stage) and the weather becomes dry, you can add back your favorite mulch.
