Kitchen Table Fix

How to Mulch Your Garden Beds the Right Way

How much mulch to buy, how deep to spread it, and how to keep it off tree trunks and your house, so it helps your plants instead of hurting them.

By Creig Boyd Jr., maintenance technician · Updated · Reviewed by Creig Boyd Jr. on

Skill
Beginner
Time
2 to 4 hours
Cost
$30 to $150
You will need
Wheelbarrow or tarp, Shovel and rake, Edging tool or flat spade, Work gloves, Tape measure, A calculator

Mulch holds moisture, blocks weeds, protects roots and makes beds look finished. Done wrong, it does the opposite. The biggest mistakes are piling it too thick and stacking it against tree trunks and the house. Here is how to do it so it helps.

Step 1: Work out how much you need

You need to know the area and the depth.

  1. Measure the bed in feet, length and width. For an odd shape, break it into rectangles and add them up.
  2. Multiply length by width to get square feet.
  3. Choose a depth, usually two to three inches. Convert inches to feet by dividing by 12 (three inches is 0.25 feet).
  4. Multiply the area by the depth to get cubic feet, then divide by 27 to get cubic yards.

For example, a 200 square foot bed at three inches deep is 200 x 0.25 = 50 cubic feet, or about 1.85 cubic yards. Bagged mulch is often sold in 2 cubic foot bags, so that is about 25 bags. Buying in bulk is usually cheaper for large areas.

Which mulch to choose

  • Shredded bark or hardwood mulch knits together, stays put on slopes and breaks down slowly. It is a good all-round choice for most beds.
  • Wood chips (often free or cheap from tree services) are coarser and last a long time, but look rougher.
  • Pine bark or pine needles suit acid-loving plants and are lighter to handle.
  • Fresh, unaged wood can tie up nitrogen at the soil surface as it breaks down. Spread it on top of the soil. Do not dig it in.

Whichever you choose, buy it from a source you trust, and avoid mulch that smells sour or like vinegar, which means it has been sitting without air and can harm plants.

Step 2: Prepare the bed

  1. Pull weeds, roots and all, and remove old matted mulch that has become hard or smells sour.
  2. Define the edge with a flat spade or edging tool, cutting a clean edge about two to three inches deep.
  3. Water the soil if it is dry. Mulch will not help dry ground.

Step 3: Spread it

  1. Spread the mulch evenly, two to three inches deep, with a rake.
  2. Keep it back from tree trunks. Leave a few inches of bare ground around the trunk. Mulch piled up against the trunk, sometimes called a mulch volcano, traps moisture and can rot the bark and kill the tree.
  3. Keep it off the house. Leave a gap of several inches between mulch and siding, and do not cover foundation vents. Mulch against the house holds moisture and can attract insects.
  4. Pull it back from plant stems so air can reach them.
  5. Rake it level, and water it lightly so it settles.

Step 4: Keep it fresh

Each year, rake the old mulch to loosen it and add a thin layer only if it has thinned below two inches. Do not pile new mulch on top of a thick old layer.

Common mistakes

  • Mulch volcanoes. The most common and most harmful mistake.
  • Too thick. It smothers roots.
  • Against the house. It holds moisture and invites pests.
  • Spreading over weeds. Pull them first.

When it is not a mulch problem

Water that pools, dead plants and insect activity need a closer look. See the list below.

Stop and call a professional if…

  • You see poison ivy, or a plant you cannot identify, in the bed. Do not pull it or burn it. Learn to identify it first, or have it removed.
  • Water pools in the bed or against the foundation after rain. Mulch will not fix a drainage problem.
  • You find signs of insects such as termites or carpenter ants at the foundation. Call a pest professional.
  • The job involves lifting heavy bags or loads that your back cannot handle comfortably. Get help or have it delivered and spread.

Would rather have someone else handle it?

If you are in Essex County, Massachusetts, PrimeFix Solutions does spring and fall cleanups, mulching, bed work, and brush and branch clearing.

Ask for a free estimate (978) 417-2042

Full disclosure: PrimeFix Solutions is my own business, so I benefit if you hire them. They do not do regulated trades such as electrical, gas and most plumbing, so for those jobs call a licensed professional.

Common questions

When is the best time to mulch?

Spring, after the soil has warmed up, is common, and fall is also good for protecting roots over winter. Avoid putting a fresh layer on when the ground is soggy or frozen.

Is more mulch better?

No. A layer that is too thick can hold too much water, smother roots and invite pests. About two to three inches is the usual advice.

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