What Is Best PH for the Nandina?

Not a true bamboo, the reed-like stems of the nandina (Nandina domestica, spp.) have earned it the common names of heavenly or sacred bamboo. An erect evergreen to semi-evergreen shrub, nandina graces summer with showy, fragrant white flowers. Reaching a mature height of 10 feet, it adds beauty to fall as bronze-green leaves turn to burgundy and big clusters of red berries dot the foliage. Thriving in U.S. Department of Agriculture plant hardiness zones 6 to 9, the highly ornamental nandina prefers soils that are highly to slightly acidic.

As an acid-loving plant, nandina does best when soil pH ranges from 3.7 to 6.4, according to the Virginia Cooperative Extension. Happy to grow almost anywhere with slightly acidic soil and mild winters; rapid-growing, drought-tolerant nandina tolerates a wide range of soil types. It can prosper in light conditions ranging from full sun to partial shade. When you add nandina’s flexible growth habits to its lack of serious disease or insect problems, you get a plant with invasive potential; nandina can easily naturalize in many landscapes.

Soil pH matters to nandina’s growth. Each nutrient the plant needs is impacted by pH. Although it can grow in highly acidic soils, the bulk of nutrients needed by nandina and other garden plants are most available in the 6.0 to 6.5 pH range. It is in this window that nutrients become most soluble, available to travel up through the roots via the soil solution. Soil pH also impacts how quickly minerals decompose in the soil, eventually turning into essential elements needed by the plant. Before setting nandina in the soil, use a hand-held pH meter to determine if your soil needs any amendments to bring its pH into the desired range.

To lower the pH of "sweet" soil and make it more acidic, add peat moss or sulfuric acid. A 2-inch layer of peat moss worked into the top 8 to 12 inches of garden beds not only lowers pH, it also adds organic matter for improved soil structure. Alternately, one-third pounds of granulated sulfur can be worked into the top 6 inches of a 10-square-foot garden space to lower the pH from 7.5 to 6. To lower pH from 7 to 6, add one-half pound. To drop from 6.5 to 6, add one-tenth of a pound. These numbers are for loam or silt-loam soil -- if you have sandy soil, reduce the amount by one-third, and cut it in half for clay soil. Soil with a pH higher than 7.5 soil resists change so resolutely that is is not practical to attempt lowering it. Lowering pH is a slow process that can take one to two years, and pH tends to increase again over time.

Although nandina can grow in highly acidic soils, bumping the pH to around 6 benefits most of the other fruits, vegetables, flowers and shrubs growing in your soil. The notable exceptions are blueberries, rhododendrons and azaleas, which prefer acidic soil. To raise the pH, work ground limestone into the top 6 inches of soil two to three months before planting. To raise pH from 4.8 to 6, add 5.5 pounds of limestone. Add 4.5 pounds to raise the pH from 5.0 to 6.0, and work in 2.5 pounds to bring the pH from 5.5 to 6. These amounts are all for a 100-square foot garden space.