Some household plants prefer mildly acidic environments. Generally, these plants will be found growing naturally in temperate regions where rainfall is common during the warm summer months. These plants flourish when they are planted in mildly acidic soil. Plants that flourish in slightly acidic environments pick up nutrients, such as nitrogen and phosphorus, more easily from acidic soil. For example, coffee, a mildly acidic substance, can be used to "water" a plant. Coffee causes some plants to flourish; however, some plants also yellow and wilt when coffee is added to the soil; it all depends on the plant.
Some household plants prefer basic environments. Most basic-environment plants grow naturally in soil that contains limestone, an alkaline rock that has degraded over millions of years and has become a component of soil. These household plants flourish when planted in basic soil, similar to that of their natural environment. Adding lime salts or an even 1:1 mixture of milk residue (left over from an empty milk carton) and warm distilled water will add alkalinity to the soil. Soils that are heavily clay, such as in the Southeast of the United States, are optimum for basic soil-loving plants.
Some plants that prefer acidic environments include african violets, gardenias, aloe plants, azaleas and hydrangeas, all temperate zone plants. Some plants that prefer more basic environments include irises, vincas and verbenas, more warm temperature plants that flourish in clay soils.