Soil pH & Blue Salvia

Why pH Matters

• A substance's acidity or alkalinity is expressed as its pH. The pH scale runs from zero to 14 with 7.0 being neutral -- low numbers are acidic, while higher numbers are alkaline. Soil's pH determines which elements are most readily available to a plant's roots. Most ornamental plants grow best in soil that's slightly acid or neutral, but there are exceptions. Azaleas and blueberries, for example, prefer very acidic soil, whereas Ponderosa pines and some vegetables require alkaline soil. Most salvias are adaptable plants, capable of good growth across a wide range of soil pH levels.

Brazilian Blue Sage

• Tall and imposing, Brazilian blue sage (S. guarantica) grows 3 to 5 feet tall and wide. The bright, indigo-blue flowers draw hummingbirds and butterflies into the garden. Grow Brazilian blue sage, also called sapphire sage, in full sun. This tender perennial adapts to a wide range of soil types and pH levels, and is moderately drought tolerant once established. Brazilian blue sage is hardy in U.S. Department of Agriculture plant hardiness zones 7 through 11.

Annual Blue Sage

• Annual blue salvia (S. farinacea) is also called mealycup sage because of the faint white hairs on the flowers that make the blooms look dusty or flour-covered. Actually a tender perennial, blue sage is grown as an annual in most parts of the country. Blue sage grows best in full sun or light shade in any well-drained, fertile soil, regardless of soil pH. The plants grow 18 to 36 inches tall, depending on cultivar. Mealycup sage is hardy in zones 8 through 11.

Hardy Blue Sage

• Several types of salvias are hardy perennials throughout most of the United States. One of the most cold tolerant is the cultivar East Friesland (S. nemorosa "East Friesland" or "Ostfriesland"), which withstands winters as far north as zone 3. Many of the hardy perennial blue sages are hybrids (S. x superba), most of which survive winters in zones 4 through 7. The hardy perennial sages prefer fertile, well-drained soil with a neutral pH around 7.0, but also grow well in both acidic and alkaline soil.

The Bottom Line on pH

• Blue salvias are adaptable plants that thrive in a wide range of soil conditions. Mealycup sage and Brazilian blue sage adapt well to a wide range of soil pH levels. Hardy salvias grow best in neutral soil with a pH near 7.0, but adapt to both acidic and alkaline soils. For all types of blue sage, soil fertility and good drainage are more important than the soil's pH.