The magic ingredient for improving the texture of either sandy or clay soils – and promoting beneficial microorganisms and adding nutrients – is an organic soil amendment. These amendments include compost, decomposed manure, aged sawdust, ground bark, peat moss or agricultural byproducts like aged cocoa and rice hulls or mushroom compost.

Flowering perennials require a steady supply of nutrients, water and air to grow, develop buds and bloom. Improve your soil with amendments to add nutrients, improve texture and drainage or to change its acid-alkaline balance.

Photo Credit: ©2001 Dolezal Publishing/Doug Dealey

Apply fertilizer in a ring around the plant’s drip line (an imaginary circle drawn beneath the perimeter of the plant’s outer foliage). The soil beneath this area contains most of the plant’s roots – they’re not beneath the plant’s center.

Photo Credit: ©2001 Dolezal Publishing/John M. Rickard

To hold moisture and nutrients in sandy soil, use a fine-textured amendment like peat moss, compost or aged manure. To loosen clay soil and add air pockets, use a coarse-textured amendment such as ground bark or rice hulls. To lower the pH of an alkaline soil, use an acidic amendment like peat moss or ground fir bark. To raise the pH of acidic soil, choose an amendment with a high pH, such as mushroom compost or steer manure.

You can raise or lower soil pH temporarily with chemical amendments. Use limestone or wood ashes to raise the pH of an acid soil toward neutral; use elemental sulfur to lower the pH of an alkaline soil. Carefully read and follow package instructions for proper chemical amounts or rely on the results of a soil test and apply them carefully, mixing the chemicals into the soil and watering well. It may take a year or more to alter the pH 0.5, and the treatment will last 2-4 years. Gypsum, a mixture of sulfur and calcium, helps correct high sodium in soil, often a problem where high mineral – or softened – water is used for irrigation, but isn’t helpful in changing pH.

To promote healthy populations of soil microorganisms, dig in compost or organic fertilizer such as alfalfa pellets sold as rabbit feed, cottonseed meal, earthworm castings or animal manure. When working with manures, use smaller amounts of concentrated, high-nitrogen bat or seabird guano than you would low-nitrogen cow or chicken manure. Some steer manures are high in sodium, which increases alkalinity.

Choose an organic soil amendment that’s aged. Fresh manure contains too much nitrogen for most plants, while fresh sawdust and hulls deplete nitrogen as they decompose. Screen the amendment to remove debris and weeds, and choose products milled and sifted to uniform consistency.

Amendments are available in bulk at landscape material yards and in bags at garden centers. They’re sold by the cubic foot or cubic yard. Two cubic feet covers 6 square feet with a 4-inch layer. One cubic yard contains 27 cubic feet and covers 80 square feet with a 4-inch layer.

Double-digging your planting bed is the best way to ready your soil for planting, add soil amendments and fertilize. The soil should be moist – neither soggy wet nor powder dry. The evening before you start, water the bed lightly. Then gather a shovel, tarp, spading fork, rake, tiller and enough organic soil amendment to cover the area 4 inches deep. While some effort is required, double-digging is easy. Just take the steps shown in the following pictures and described in their captions.