Amid the panoply of fertilizer recommendations gardeners hear from well-intentioned friends and experts, you may have been told to apply lime to your flowers. In some cases, lime might be just what the horticulturalist ordered, but you should also use care. In some circumstances and with some flowers, lime may do more harm than good.
Lime changes the pH of your soil and, therefore, indirectly affects nutrient availability as well. Lime raises pH, making the soil more alkaline. As the University of Florida IFAS Extension explains, changing the pH of your soil also affects which nutrients become most readily available. Raising the soil pH can combat toxic levels of aluminum or help correct deficiencies in nitrogen and calcium. However, alkaline soils are more susceptible to deficiencies in iron, manganese, zinc and boron.
Before applying lime to your flower gardens, contact your local extension office and have a soil test performed. Soil testing not only determines the pH of your soil, but the extension office can determine whether lime would be beneficial to your garden and, if so, how much should be applied.
Plants vary in terms of the types of soil they will prefer or tolerate. Several species of flowers prefer alkaline soils and benefit from lime applications when warranted by your soil conditions. The University of Minnesota Extension provides a list of alkaline-loving plants, which include yarrow, clematis, phlox, coneflower, daylily and salvia.
When applying lime to your flower gardens, the Virginia Cooperative Extension recommends applying it in 5-lb. increments for every 100 square feet until you reach the recommended amount. Space applications by one to six months. Rake the lime into the top inch of soil and rinse off any that comes in contact with your plants. If you're applying lime to a new garden, it can be applied in 10-lb. increments for every 100 square feet, working it into the top 5 inches of soil. Wood ash is another liming agent suitable for use with flowers. The Oregon State University Extension recommends working a 1/2 to 1 lb. of wood ash into the soil around your perennial flowers and shrubs.
Not all flowers like alkaline soil. Rhododendrons and azaleas, in particular, prefer an acidic soil, so avoid liming them. In addition, as the University of Florida IFAS Extension points out, lime applications to change soil pH are temporary. You will need to continue testing, evaluating and applying lime on a regular basis in order to raise soil pH over the long term.