How to Use Mulch in Your Garden

Here at Perfect Plants Nursery, we love our mulch! If we see a patch of bare soil, we mulch it! Nature doesn’t allow bare soil, and we shouldn’t either. Learn how to use mulch in your garden!

Why Use Mulch?

If you are starting a new flower bed or planting a vegetable garden, you should use mulch and reapply as often as needed thereafter. Here are 6 reasons to use mulch in your garden beds or raised beds.

  1. Reduces evaporation from the soil surface and holds moisture in.
  2. Acts as a weed barrier to smother weeds, and prevents weed seeds from germinating.
  3. Insulates the soil from temperature fluctuations, keeping the soil around plant roots warmer on cool spring nights, cooler during hot summer days, and warmer during frosty winters.
  4. Organic mulches eventually decompose and become part of the soil, adding fertility and structure.
  5. A layer of mulch protects the ground from pounding rains and reduces soil erosion.
  6. A layer of mulch around plants, in flowerbeds, and between border plantings is appealing to the eye and looks better than bare soil.

Is Mulch Organic Matter? Organic vs. Inorganic Mulch

Inorganic mulches include pebbles, gravel, pumice rock, shredded rubber mulch and landscape fabric. Inorganic mulches are useful on pathways, under roofs and eaves, and where foot traffic is heavy and we don’t intend to grow plants.

Organic material include leaves, wood chips, pine bark nuggets, shredded bark, grass clippings, pine needles, compost, straw, and hay. We use organic mulch around trees and shrubs, in vegetable gardens, and in flowerbeds.

Different types of mulch can be fine textured, like sawdust, or coarse textured, like bark chips. The former can be impenetrable to air and water, and the latter can be too porous to the job. In most situations, we prefer mulch with an intermediate texture.

Best Mulch for Vegetable Gardens

We like hay as mulch for our home flowerbeds and vegetable gardens. We ask for last year’s hay, which costs less than fresh hay because it is less desirable for livestock feed. It’s least expensive if you get it in those big round rolls. You can use straw, but we prefer hay because it is softer and easier to work with. Some garden writers say that using hay as mulch results in weeds and unwanted grass due to seeds in the hay. That has not been our experience. It is true that some hay has seeds in it, but any seeds that do germinate in the upper layers of the hay quickly dry out and die, and any seeds germinating in the lower layers are soon smothered. Hay is not the most attractive mulch, and we sometimes cover it with a thin layer of pine straw just for looks.

Throw the hay out on the garden a foot or more thick, packing it between rows or individual plants as necessary. The hay soon settles into a nice smooth carpet, smothering weeds and retains moisture in (rain or watering speeds up the settling). To plant small seeds, use a board to push the hay side to side creating a gap a few inches wide. Then use the end of the board to create a narrow trench down the center of the gap, and sow the seeds in the trench. For large seeds and small plants, just carve out a gap in the hay you’re your fingers.

The hay decomposes into the garden soil in just a few weeks. You should throw more on as needed and as weeds begin to poke through. After a few years of using hay as garden mulch, the soil beneath the hay is black, friable and full of earthworms.

How to Mulch Around Trees & Shrubs

It is always important to install a layer of mulch around newly planted shrubs, trees and perennials for all the reasons listed above. And in addition, a mulch zone around a new shrub or tree trunk can help protect it from lawn mowers, string trimmers and other physical threats. We recommend organic mulches such as hay, straw, pine needles, bark chips, composted wood chips or shredded leaf mulch. If you use hay or straw, you might want to cover it with a layer of pine straw to make it look nicer.

Right after planting a young tree or shrub, add a layer of organic mulch 2-6” deep around the tree or shrub and out as far as its crown extends or even further. Do not layer the mulch more than 6” deep. This could keep the soil too moist, reducing oxygen and encouraging root rot, especially on soils that are already moist or not very well drained to begin with. Instead of piling it on too deep, reapply mulch in a few months when it has partially decomposed.

Do not let the mulch touch the trunk of the plant like a mulch volcano. Instead, make a donut hole by leaving a zone of at least 6-10” of bare soil right around the trunk. If the mulch touches the trunk, it could encourage tree root growth in the mulch, which could eventually girdle the trunk. Mulch right up against the trunk can keep it too moist and encourage decay and diseases. Mulch up to the trunk can become habitat for rodents and other critters that might chew the bark or otherwise damage the trunk.

Sheet Mulching for New Vegetable Gardens and Flower Beds

The best way to get a new flowerbed or vegetable garden off to a great start is to sheet-mulch. Sheet-mulching (also known as sheet-composting) is the process of making compost right where it’s needed by successive layering of carbon-rich and nitrogen-rich materials. As you would in a compost pile, only right on the ground where your new plantings will be. Here’s how to sheet-mulch:

Do not dig or till the soil; we do not want to disrupt the physical structure, living microorganisms and ecological processes in the undisturbed soil. Don’t pull up any weeds. Knock ‘em down or cut them. But leave them on the ground to be smothered so they will decompose and add their nutrients into the soil. You can sheet-mulch right on top of undisturbed lawn sod.

Start by watering the area deeply with a garden hose or sprinkler. If a prior soil test has determined that your soil needs amendments such as garden lime, rock phosphate, elemental sulfur, or other minerals, spread them on the surface of the ground. Next, add a layer of nitrogenous material such as grass clippings or manure, etc. to a depth of 1-3 inches thick. Wet it down some more. Add at least a ¼” layer of cardboard or non-glossy newspaper sheets, overlapping the sheets so there are no gaps. This thick layer ensures that weeds or grasses will not grow through the mulch. Wet down thoroughly again. Add another 1 inch layer of green nitrogenous materials, such as manure, fresh grass clippings, or kitchen scraps. You have now “sandwiched” the carbon (cardboard or layers of newspaper) between two nitrogen layers. Wet down again.

Related: How To Landscape Around Trees

Now add another top layer of carbon materials such as leaves, straw, hay, or finely shredded branches. Wet down thoroughly once again. If you have it, add 1-3″ layer of compost to inoculate the sheet-mulch with beneficial bacteria, fungi, and other microbes. This will speed up the composting process but is not mandatory. Wet the pile down again. For aesthetics, add a 2” layer of wood chips, bark mulch, leaves, or pine needles.

You should sheet-mulch your new bed the growing season before you plan to plant. If you don’t want to wait, you can cut holes through the layers and plant directly in the soil beneath.

Keep your garden healthy and weed free with mulch!