10 Plants for Gardens with Alkaline Soil

For beautiful, healthy plants, you may need to adjust the pH of your planting site (pH is a number between 0 and 14 that refers to how acidic or alkaline your soil is). A soil test kit, available online or from garden centers and hardware stores, measures the pH, so you’ll know whether or not your soil needs amendments.

The first step in testing is taking dry soil samples from different parts of your garden. Mark the test tubes from the kit to indicate where each sample came from (the pH may vary across your planting site, requiring different amendments in different places). Mix the soil with the chemical solution in each tube.

Now compare the solution colors to the chart in your kit. Dark green indicates alkaline soil (a pH above 7). Bright green is neutral (a pH of 7). Yellow and orange indicate acidic soil (a pH below 7).

Deutzia gracilis can adapt to a wide range of pH levels. This deciduous shrub is happy in mildly alkaline soil, as long as it drains easily and stays moist, but not wet. Deutzias bear clusters of small flowers in spring and are attractive in winter, thanks to their peeling bark. This variety, 'Yuki Cherry Blossom' explodes with pink petals each spring.

Better known as bluebeard, Caryopteris x clandonensis is a woody perennial with aromatic, gray-green leaves. From late summer into fall, it bears clusters of bluish-purple flowers. This attractive plant is adaptable enough to grow in neutral, slightly acidic or slightly alkaline soils. If your garden spot is strongly alkaline, you can "sweeten" it, or decrease the alkalinity, by adding organic matter, garden sulfur or sphagnum peat or by mulching with acidic pine needles.

Clematis vines prefer neutral to slightly alkaline soils. Some gardeners with acidic planting sites add lime or wood ash to adjust their pH, but check the results from your soil test before you add or reapply amendments. Wood ash, for example, breaks down fast and has to be reapplied often, which can get your soil out of balance. This clematis, 'Hakuba,' has pale lavender blooms brushed with light green. The flowers, which are are magnets for butterflies, open in late spring and gradually become white.