Although most plants thrive in slightly acidic to neutral soil, a variety of perennials and shrubs are alkaline-loving plants, including perennials such as hellebores, clematis vine, dianthus, purple crocus, clematis and potentilla. Akaline-loving shrubs include Green Velvet boxwood, photinia, spiraea, Worcester gold, forsythia, lilac, crab apple, California lilac, Great Orme hebe and mock oranges.
Although finding plants to grow in alkaline soil (soil with a pH above 7.0) can be tricky, alkaline soil typically drains well and warms faster in spring than acidic soil. When planting perennials or shrubs in alkaline soil, mix a good amount of compost or well-rotted manure into the soil to boost the nutrient content and help the soil retain water.
Gardeners who are unsure of the pH of their soil may buy a pH testing kit online or at a local garden center. Soil that is overly acidic with a pH below 7.0 can be made more alkaline by working ground limestone into the soil. Garden centers typically carry ground limestone in several forms including pelletized, granular, pulverized and hydrated. Another way to increase soil pH is with wood ashes, which are less effective than limestone. On the upside, wood ashes contain high levels of calcium and potassium.