A person wearing blue and gray work gloves holds a cupped handful of reddish-brown wood mulch.

Mulches & Soils

Whether you're planning a new garden bed or maintaining a mature landscape, our FAQs have the answers to common questions. Learn the right techniques for applying mulches and soil to ensure a healthy, thriving foundation for your lawn and garden.

Mulch & Soil FAQs

What is growing in my bag of mulch or soil?

Why do I sometimes find mold or fungus growing inside a sealed bag of soil or mulch?

If you open a new bag of soil or mulch and find white mold or fungal spots, it's a direct result of moisture content. Mold and fungus thrive in moist environments containing organic matter. Since soil and mulch bags are not always perfectly waterproof, water content from the original packaging (especially in colored mulch, which retains moisture from the dyeing process) or moisture seeping in after packaging provides the ideal conditions for these harmless organisms to develop.

The mold and fungus found in soil or mulch bags are generally harmless. They are natural organisms that help break down organic matter and contribute to the health of your garden, rather than damaging your plants. They pose no risk to people or pets, though wearing gloves when gardening is always a good idea.

If you see mold on the exterior of a bag of soil or mulch, do not purchase it. This may indicate improper storage conditions and potential contamination. Unlike mold found inside the bag (which is often harmless), external mold suggests a compromised product.

Fungi, including mold and mushrooms, are essential components of a healthy soil ecosystem. These beneficial microorganisms perform a vital function: they break down organic material into readily available nutrients that your plants can easily absorb. This process is so crucial that we deliberately choose not to sterilize our growing media, ensuring we preserve these natural helpers that enrich the soil and foster balanced conditions for robust plant roots.

If you notice a large, unattractive amount of mold, it's typically a sign that the soil or mulch is too wet. While this overgrowth is not harmful to your plants, you can easily reduce or eliminate it by exposing the media to sunlight and air.

  • For Unused Soil/Mulch: Spread the product out on sheets of newspaper or a tarp and allow it to dry out before application.
  • For Soil/Mulch that is already applied: Allow the area in your garden to dry out a bit by reducing the frequency of your watering.

The mold should naturally dissipate once the moisture level decreases. Remember to always wear gloves when handling any growing media product.

 A bag of Miracle-Gro Organic All Natural Mulch stands next to a wooden raised garden bed in a backyard, with established shrubs and a lawn in the background.

Since moisture is the main driver of mold growth inside bags, choosing a product with lower water content will help. We recommend Miracle-Gro Organic™ All Natural Mulch. This product is undyed, meaning it carries less residual moisture from the coloring process, which in turn leads to less mold development. Even if you see some mold in any mulch or soil, remember it's a natural occurrence that helps enrich your garden.

How Does Mulching Help?

It Adds Curb Appeal

Mulch is the key to achieving a finished, professional look in your yard. It immediately adds rich color and texture to areas like landscape beds, around trees and shrubs, or along your home's foundation. Choosing a colored mulch offers the added benefit of beautifully accenting and harmonizing with the existing colors of your home and flower gardens.

Mulches made from wood and other organic materials are valuable because they actively improve the soil as they decompose. Over time, natural soil inhabitants like microbes and insects consume the mulch. The by-products of this natural consumption are released back into the soil as organic matter, leading to healthier, more fertile growing conditions.

Mulch functions as an effective insulator, playing a critical role in regulating soil temperature throughout the year. It keeps plant roots cool during the heat of summer and provides essential warmth and protection during the winter months. This insulating property is particularly vital for tender, new plantings established in the fall, offering necessary defense as temperatures begin to drop dramatically.

Mulching directly contributes to reduced watering time because it acts as a barrier to moisture evaporation. By slowing down this process, mulch ensures that more water remains conserved in the soil, readily available to nourish thirsty plant roots.

Applying a 2 to 3-inch layer of mulch provides a natural, effective barrier against weeds. This works by blocking sunlight and physically suppressing growth, which prevents weed seeds from sprouting and taking over your landscape beds.

Three bags of Earthgro by Scotts mulch in red, black, and brown, arranged on a stone border with a dark mulched garden bed in the foreground and greenery in the background.

Mulches come in various forms (wood, rock, synthetic), but to gain the essential benefit of soil improvement, consider choosing a wood mulch. Premium options like Scotts® Nature Scapes® Color Enhanced Mulch and Scotts® Nature Scapes® Triple Shred Mulch are made from natural forest materials, offering rich color that lasts up to a year. When choosing a color, select a hue that complements your home (e.g., brown or red for brick). While darker mulch makes flowers stand out, be aware that black mulches absorb heat, so lighter colors are recommended in very warm climates to prevent plant overheating. Overall, mulching is a quick and simple way to enhance your landscape and improve the growing environment.

How much mulch do I need?

A table titled "Help with calculating the number of 1.5CF bags of mulch" showing coverage at a 3" depth. The table lists 1, 2, 4, and 6 bags covering 6, 12, 24, and 36 square feet, respectively.
Number of 1.5CF Bags Coverage at 3" Depth

1

6 sq. ft.

2

12 sq. ft.

4

24 sq. ft.

6

36 sq. ft.

Application Tips for Mulch

Should I remove old mulch before applying new mulch?

In most situations, there is no need to remove old mulch since it will naturally decompose and enrich your soil. The only time removal is necessary is if the layer is excessively thick (over 4 inches). If you choose to leave the old mulch, always be sure to loosen it up before adding a new layer. This simple step is vital for improving both drainage and airflow in the soil beneath.

As a general rule, applying fresh mulch to your landscape or garden beds once a year is recommended.

What can I grow with soil in my raised bed?

What can I grow in a 6" raised bed?

Arugula, leeks, lettuce, onions, radishes, spinach, strawberries, basil, chives, cilantro, dill, mint, oregano, parsley, thyme, marigolds and other annual flowers

Beans, beets, broccoli, Brussels sprouts, cabbage, cantaloupe, carrots, cauliflower, collards, cucumbers, garlic, kale, summer squash, Swiss chard, turnips, lavender, rosemary, sage, borage, calendula, cosmos, lantana, nasturtiums, snapdragons, sweet alyssum (plus everything in the 6" list)

Artichokes, asparagus, eggplant, okra, parsnips, peppers, sweet potatoes, tomatoes, watermelon, winter squash, pineapple sage (plus everything in the 6" and 12" lists)

Start feeding your plants with Miracle-Gro® Raised Bed Plant Food one month after planting, following label directions. This combination, particularly when using Miracle-Gro® Raised Bed Soil, guarantees more abundant yields (compared to unfed plants). For subsequent planting seasons, instead of replacing all the soil, simply renew it. Before planting, mix in Miracle-Gro® Refresh™ Soil Revitalizer as directed. It is designed to rebuild soil structure, enhance water retention, and replenish essential nutrients, keeping your garden beautiful and productive.

How much soil do I need for a raised bed?

A table answers the question, "How many bags of soil do I need for a raised bed?" The table shows bag requirements for three different raised bed sizes, 2 feet by 2 feet, 4 feet by 4 feet, and 4 feet by 8 feet, at three different depths: 6 inches, 12 inches, and 20 inches. The table provides two different bag sizes for each calculation
Area 6" 12" 20"

2ft. x 2ft. Bed

2 Bags 1.5CF

2 Bags 1CF

3 Bags 1.5CF

4 Bags 1CF

5 Bags 1.5CF

7 Bags 1CF

4ft. x 4ft. Bed

6 Bags 1.5CF

8 Bags 1CF

11 Bags 1.5CF

16 Bags 1CF

18 Bags 1.5CF

27 Bags 1CF

4ft. x 8ft. Bed

11 Bags 1.5CF

16 Bags 1CF

22 Bags 1.5CF

32 Bags 1CF

36 Bags 1.5CF

54 Bags 1CF

How much soil do I need for an in-ground garden?

A table answers the question, "How many bags of soil do I need for in-ground?" It provides bag requirements for an area at a 3 inch depth. The table lists three areas in square feet: 24, 48, and 72. For each area, it lists the number of 1.5 cubic foot (CF) bags and the number of 1 cubic foot (CF) bags required. Specifically, 24 square feet requires 4 bags of 1.5 CF or 6 bags of 1 CF; 48 square feet requires 8 bags of 1.5 CF or 12 bags of 1 CF; and 72 square feet requires 12 bags of 1.5 CF or 18 bags of 1 CF.
Area (sq. ft.) 3" Depth

24 sq. ft.

4 Bags 1.5CF

6 Bags 1CF

48 sq. ft.

8 Bags 1.5CF

12 Bags 1CF

72 sq. ft.

12 Bags 1.5CF

18 Bags 1CF

Did the indoor potting mix formula change?

There were no formula changes. This packaging refresh was done with you in mind to make the shopping experience simpler, and to drive understanding of the plant types each product should be used with and the area of usage that the products are designed for.