Does pine bark mulch make soil acidic? (2023)

What is the pH of pine bark mulch?

pH of Pine Bark

Pine bark should have a natural pH between 4.0 and 5.0, ideal for blueberries.

Mulch. Use organic mulch in your garden beds. The material will break down over time, helping to make soil more acidic in the process. Mulching with pine needles or oak leaves can provide an acidic boost.

Pine needles are naturally acidic as they break down, making them excellent for mulching around plants that prefer acidic soils (azaleas, rhododendrons,camellias, etc.) During heavy rain events, pine needles tend to stay put and not wash away, making them an excellent choice on slopes.

The assumption that bark mulch has a low pH value is based on the quality of the source material. Bark of conifers is the main raw material in bark mulch and is, indeed – at least initially – on the acid side of neutral. However, its pH value gradually increases as the mulch material decomposes.

Pine Bark Benefits

Commercial pine bark products are usually made from the byproducts of milled wood. Finely ground pine bark works well as a soil conditioner because it helps the soil retain moisture, and adds “pore space” into the soil, through which oxygen and nutrients can filter.

Two types of material can be used for soil acidification: elemental sulfur, which yields relatively rapid results, and nitrogen fertilizer, which acts more slowly. If soil acidification is needed, most homeowners want quick results, so elemental sulfur is the best option.

Pine Bark Mulch and Soil Acidity

Pine bark is naturally acidic, and over time that acidity can transfer to the soil, reveals New Jersey Agricultural Experiment Station. Many garden plants grow best in neutral or alkaline soils.

They will draw more nitrogen from the soil and that can damage your plants. Bark mulches add acidity to the soil and can disrupt the pH balance. Make sure you choose the right mulch for your plants before you add it to your soil.

Which is better hardwood mulch or pine bark mulch?

Shredded hardwood is even better at trapping moisture than hardwood bark mulch. It also decays faster and adds more nutrients to the soil as it does. The shredded pieces also hold together better than the large pieces of bark. As a result, they are better for laying in sloped areas because they won't roll away.

Pine bark is more acid (lower pH) than other mulches, which is very beneficial for most landscape plants. It also uses less nitrogen to decompose, so less fertilizer is needed to keep plants healthy. A few years ago we discovered pine fines, “the Cadillac of mulches”.

The average value of pH of pine wood was 4.50 ± 0.04 and in the case of spruce wood, the measured pH value was 4.79 ± 0.11 (Figure 2).

Bark mulches add acidity to the soil and can disrupt the pH balance. Make sure you choose the right mulch for your plants before you add it to your soil.

The pH of our bark is on the acid side of neutral, pH5-6. In comparison, peat is usually in the range of pH3-3.5. Because bark lies on the soil surface, it allows for the passage of rainwater and air into the soil, and therefore has no harmful effect on the soil's pH.

The bark of all trees showed acidic reaction ranging from pH 2.2 to 4.7.