Some people enjoy warm weather with a beach view, while others prefer snow and mountains. Likewise, some types of plants perform better when their preferences are met, particularly regarding the acidity of the soil in which they grow. Plants preferring alkaline soil will not thrive in an acidic environment and vice versa. If you know your soil tends to be acidic, knowing which plants prefer a lower pH is useful for ensuring a successful garden.
About Soil Acidity
Soil acidity, or the measure of hydrogen ions in a given sample, can be determined by a pH meter or soil sample test. Most home improvement stores and garden centers have simple pH meters available intended for home testing. Highly acidic soils will have a lower pH, from 1.0 to 6.0, while alkaline soils have a high pH, from 8.0 to 11.0. A wide range of plants prefer neutral, or pH level 7, to slightly acidic soils. Overly acidic soils can be adjusted towards neutral by incorporating lime compounds and alkaline soils can be adjusted in the other direction using nitrogen fertilizers, sphagnum peat moss or aluminum sulfate.
Flowering plants which prefer acidic to slightly acidic soils include garden favorites like bleeding heart (Dicentra spp.), creeping phlox (Phlox stolonifera) and most types of daylilies (Hemerocallis spp.). Less well-known but worth consideration for acidic soils are plants including crested iris (Iris cristata), butterfly weed (Asclepias tuberosa), Japanese iris (Iris ensata) and false indigo (Baptisia australis).
Ferns and Groundcovers
Except for Christmas (Polystichum acrostichoides) and maidenhair (Adiantum pedatum) ferns, a good number of ferns prefer slightly acidic sites, including tall stately ostrich ferns (Matteuccia struthiopteris), cinnamon fern (Osmunda cinnamomea), and the smaller, lacier, lady fern (Athyrium filix-femina). Suitable groundcovers include partridgeberry (Mitchella repens), wintergreen (Gaultheria procumbens), scotch heather (Calluna vulgaris), grass-like sedges (Carex spp.) and even oregano (Origanum spp.)
In the shrub category, a bigger problem for the gardener may be which acid-loving plants to exclude, as many popular shrubs prefer acidic sites. Blueberries (Vaccinium spp.) are one of the best types of shrubs to select for very acidic soil, especially in moist areas with abundant sunshine. Evergreen selections include rhododendron and azaleas, as well as mountain laurel (Kalmia latifolia), American holly (Ilex opaca) and junipers (Juniperus species). Flowering choices include white fringetree (Chionanthus virginica), viburnum (Viburnum spp.), and witch alder (Fothergilla spp.).
- Rutgers New Jersey Agricultural Experiment Station: Soil pH and Lime Requirement for Home Grounds Plantings
- Ohio State University: General Maintenance of Herbaceous Ornamentals
- Maryland Cooperative Extension: Ground Covers
- University of Minnesota Extension: The Best Plants for 30 Tough Sites
- Marin College: Shrubs of Marin
- Marin College: Marin Ferns and Fern Allies
- Dynamic Graphics Group/Dynamic Graphics Group/Getty Images