Mulch or Rock in Landscaping: Advantages, Disadvantages, and Application Tips

Ten yards of mulch, done! I should have bought 15 yards to finish off my gardens nicely, so I will make note of that so I order the right amount next time. One of the first questions many people have when completing a new garden or landscape project is “Should I use mulch or rock?” Well, here are my two cents:

Homeowners use mulch or rock to keep weeds down, keep moisture in the ground, and/or provide a certain look to landscaping. Some people love the look of rock, some may prefer the more natural look of mulch, and some go without either. If you have a garden in which you like to move things around, plant annuals, frequently add new plants, or like a more natural look, use mulch. On the contrary, if you have an area that will not be disturbed for years (ex. a walking path, or an area with shrubs), if you want something that lasts a little longer, or you like the look of stone, you may be safe using rock. Here are the pros and cons of using mulch and rock along with application tips for both:

Mulch Pros:

• Keeps soil moist.
• Insulates well! Helps to keep plant roots and soil cool during warm periods, and helps keep the soil warm during cool periods.
• Breaks down over time and enriches the soil by adding nutrients from the decaying wood.
• Prevents weeds from growing.
• Mulch is easily moved and replaced when a plant needs to be planted.
• No barrier is needed before laying down mulch
• Relatively lightweight, so most homeowners can apply mulch on their own.
• Inexpensive – Costs two to three times less than rock.
• Has a natural appearance.

Garden space that hasn’t been mulched in two years.

Garden space after 3″ of fresh mulch has been added.

Mulch Cons:

• Due to the lightweight-nature of mulch, heavy rains or strong winds can misplace mulch.
• Due to the natural decomposition of wood, mulch needs to be replaced or refreshed every other year.

Mulch Tips:

• Remove weeds before applying mulch.
• Use 3-5″ of mulch to keep the weeds down and to keep the water in the soil.
• Lay down 3-4″ of smaller-sized mulch, and 5″of larger-sized mulch to prevent weed growth and retain water.
• Plant and transplant before new mulch is added.
• Remove mulch before planting, and reapply mulch after planting.
• Apply mulch in the early spring. Mulching while plants are small makes spreading the mulch much easier with very little chance of ruining emerging plants.

Rock Pros:

• Rock comes in many different colors, textures, and shapes.
• Rock is durable and rarely has to be replaced.
• Helps to keep moisture in the soil.

Rock Cons:

• Very heavy and can be very difficult and expensive to install.
• Costs two to three times more than mulch.
• Needs a barrier, such as landscape fabric, between the soil and rock.
• Can heat up the ground causing plant or root damage.
• Debris can build up in-between rocks causing weeds to grow.
• Rocks with dirt in them need to be lifted and cleaned to prevent weeds to grow.
• The barrier under the rock does not allow natural decomposition of materials in to the soil.
• Very hard to remove once installed.

Rock Tips:

• Remove weed from soil before barrier and rock are applied.
• Add 2-4″ of rock (smaller rock being on the 2″ range and larger rock being up at the 4″ range) on top of barrier.
• Blow debris off of rock whenever needed so it doesn’t have time to decompose.
• Have shrubs or trees planted before laying barrier and rock down.
• Do not plant after rock is down.
• Use around shrubs and trees only. Rock can heat smaller or fragile plants too much, causing damage to plant and/or roots.