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In some areas of the country, the choice between mulching with pine needles and wood mulch is a tough one. Since the 1980s, pine straw has been the favorite mulch in the South. It is inexpensive, effective, and attractive, especially in the vicinity of the ever-present loblolly and longleaf pines.
Like most mulches, pine needles contribute valuable organic matter to the soil, supporting an impressive diversity of native and ornamental landscape plants including trees, shrubs, perennials, and annuals. If you’re considering pine straw for your landscape, here are a few things you should know.
1. Pine straw mulch is lighter in weight than wood mulch.
Mulch weight might not be the first thing on your mind as you begin a spring landscape cleanup. But after loading up, unloading, and spreading a few bags, your arms and back might start asking questions. Wood mulch is deceivingly heavy, but pine straw can be deceptively lightweight.
The best way to compare the two is by taking a look at coverage per pound. A single bale of pine straw, which weighs about 35 pounds, covers about 50 square feet. Compare that to a standard 2-cubic-foot bag of wood mulch, which weighs about 25 pounds and covers 12 square feet.
The pine straw covers close to 1.5 square feet per pound, while wood mulch covers about 0.5 square feet per pound. That’s one-third the weight per square foot of coverage, or three times the coverage per pound by pine straw.
2. Many gardeners prefer long-leaf pine straw.
Garden-center shoppers may find two types of pine needles for mulch to choose from: Long-needle pine straw comes from the longleaf pine tree, and its needles are 12 to 18 inches long. Short-needle straw—4 to 8 inches long—comes from loblolly or slash pine trees.
Long-needle straw is thicker and coarser and tends to decompose more slowly than short-needle straw. Many gardeners find the reddish hue of long pine needles to be appealing; short needle straw is light brown.
3. Pine straw mulch can be sustainable.
The mulch pine straw that is sold in stores and landscape supply centers is harvested from timber farms. These privately held properties are managed for a diverse set of goals, so measuring the environmental impact of the straw harvest is a complex undertaking that differs from one property to the next.
But, homeowners who have loblolly or longleaf pine trees in their own yards can take advantage of fallen needles by reusing them to mulch the landscape, rather than bagging and disposing of the needles. It’s free mulch, and you only have to pick out the cones and sticks. This pine needle mulching is a more sustainable way to keep the driveway, lawn, and deck clear, while protecting and beautifying landscape beds.
4. Pine straw mulch is significantly less expensive than wood mulch.
To compare the cost of pine straw versus mulch, look again at the coverage per bag of mulch versus coverage per bale of pine straw. It’s pretty common to see 2-cubic-foot bags of wood mulch for sale at three for $10, or $3.33 each. Since each bag covers 12 square feet, that’s 36 square feet for $10, or 3.6 square feet per dollar.
At an average cost of about $4 per bale, and each bale covering about 50 square feet, pine straw comes in at 12.5 square feet per dollar. Buying pine straw for mulch instead of traditional wood mulch stretches a dollar nearly 3.5 times further.
5. Pine straw is an excellent insulator.
In addition to conserving moisture, preventing erosion, and blocking weeds, pine straw mulch also helps to keep the soil cool in summer and warm in winter. Its lofty structure creates trapped air space, like a blanket. The trapped air resists daily air temperature swings due to daytime and nighttime differentials, and warm or cold fronts passing through.
It takes long-term heat or cold due to seasonal changes to affect the soil temperature beneath the mulch layer. So, pine straw protects plant roots both in summer and in winter.
6. Pine needles maintain soil moisture well.
The same qualities that allow pine straw mulch to protect soil from temperature swings also help conserve soil moisture. Water perks into and evaporates out of soil through tiny pore-like channels. This well-defined structure is a sign of good soil health and also allows plants to establish deep root systems. If the soil surface is unprotected from the sun’s rays, it dries out quickly.
Using a layer of pine needles as mulch on the soil surface creates trapped air space that allows liquid water to pass through into the soil. But because of their cooling effect, the needles greatly reduce moisture loss through evaporation.
7. Pine straw mulch should be spread 3 inches deep.
Be sure to wear gardening gloves when handling pine straw mulch as it can be quite prickly.
- First, snip the string or wire that’s holding the bales together. Often the bales are composed of compressed layers of mulch.
- Select one of these layers and begin pulling it apart, shaking the mulch across your garden beds.
- Using your hands or a bow rake, spread the mulch to about 3 inches deep across the soil.
8. Pine needle mulch will last as long as a year.
Depending on your environment, an application of pine needle mulch will last 6 months to a year before degrading to the point at which you need to apply a fresh layer. Climate, erosion, and aesthetic preferences will impact the amount of time you can go before needing to apply new mulch. When it comes time to spread more pine needle mulch, don’t remove the old pine straw. Leave it to continue to decompose and enrich the soil.
9. Pine straw mulch isn’t the best option for preventing weeds.
While pine straw makes an excellent protective covering to maintain soil temperature, structure, and moisture levels, it does have a disadvantage. Compared with other types of mulch, using pine needles for landscaping does not do a great job of smothering weeds. Using pine straw as mulch allows moisture and light to penetrate deeply into the surface, which encourages weed seed germination. It also makes a wonderful habitat for trailing perennials like Virginia creeper, Bermuda grass, poison ivy, and others to spread where they’re not wanted.
Control weeds in mulched areas by maintaining a 3-inch-deep layer of pine straw, applying weed preventer, pulling weeds before they go to seed, and by spraying judiciously with liquid weed killer.
