If your yard is covered with pine needles from several mature pine trees, use the needles as landscape mulch rather than bagging and discarding them, especially around plants that benefit from pine needle mulch. Pine needles are acidic when they're green and may increase acidity in soil, but they become more neutral over time as they decompose. Planting acid-loving flowers and shrubs that benefit from the pine needle mulch reduces your work and benefit the plants.
Flowers that love acidic soil include Lily of the Valley, dianthus, yarrow, iris, orchid, pinks, rue, hosta and veronica. Some of these flowers, such as hosta and Lily of the Valley, prefer the shade under pine trees. If there is sufficient room between the tree's roots, you can plant these flowers directly to the soil so the pine needles naturally fall down around them. Mature pine trees have large roots that are difficult to plant around; build a raised bed for flowers under these trees.
Shrubs that benefit from pine needle mulch include azalea, gardenia, hydrangea, jasmine, rhododendron, bayberry, Daphne rose and holly. Gardenias need a monthly application of an acidic fertilizer. You can replace it with a layer of pine needles smoothed around the base of the shrub. Gardeners use an acidic fertilizer to turn hydrangea's flowers blue. Try using pine needle mulch under the hydrangeas instead.
Amending the Soil
To determine whether the soil's pH needs to be amended, test the soil in the garden. Take a sample to the local agriculture extension agency or use a soil testing kit purchased from a gardening center.
To reduce the pH by 1.0 points, mix 1.2 ounces of ground rock sulfur for each square yard of sandy soil, or 3.6 ounces per square yard for all other soils. Amend the soil two to four weeks ahead of planting to allow the amendments time to adjust the soil's pH.
Getting Pine Needle Mulch
You can collect pine needles from your own yard if you have pine trees growing on your property. If there aren't any pine trees in your yard, buy pine needle mulch, also known as pine straw, from home garden stores or nurseries.
If you live in an area with pine trees, watch for neighbors who rake and bag their mulch to put out for the trash. Ask if you can have the needles.
Using Pine Needle Mulch
Remove weeds from the area before applying the pine needle mulch. While mulching can help control weeds, it's easier for the mulch to do the job when you start with a weed-free area.
Spread the pine needles around the plants to the drip line, leaving it about 2 to 3 inches away from the plant base or shrub trunk. Wearing gardening gloves helps protect you from pokes from the pine needles. Keep the pine needle mulch around 3 to 4 inches deep. Too shallow a depth won't control the weeds or help the soil retain moisture. Mulch that is too deep keeps the soil too wet, causes disease, rots the roots and attracts rodents and other pests.
Reapply the pine mulch every year. You can add more pine mulch twice per year if you're using it for decorative purposes and want to freshen up the look.
After attending Hardin Simmons University, Kay Dean finished her formal education with the Institute of Children's Literature. Since 1995, Dean has written for such publications as "PB&J," Disney’s "Family Fun," "ParentLife," "Living With Teenagers" and Thomas Nelson’s NY Times bestselling "Resolve." An avid gardener for 25 years, her experience includes organic food gardening, ornamental plants, shrubs and trees, with a special love for roses.