Soil Prep for Boxwood

Soil pH

• The soil's acidity level, or pH, ranges on a scale from zero to 14, with zero being highly acidic and 14 being completely basic. A pH reading of seven is completely neutral. Boxwoods prefer slightly acidic to slightly alkaline soil, and will generally thrive in soils with a pH reading between 5.5 and 7.5. Otherwise, your shrubs may experience stunted growth or discoloration.

  To test the soil's pH level, contact a local garden center or extension service for a soil test. You'll collect a number of soil samples from your planting area and send them to a lab to be tested for acidity level. You should conduct this test four to six weeks before you intend to plant your boxwoods so you can receive the results and make adjustments as necessary.

Adjusting pH

• When you get your soil test results back, you'll see your soil's pH level, and will find recommendations for how to adjust the pH as necessary. If your soil is too acidic--i.e., if the number is too low--an application of dolomitic lime will make it more alkaline. For soil that's too alkaline (with a high pH number), sulfur will make the area more acidic. The actual amount of the material you must apply depends on the pH level and how much it needs to change, as well as on the size of the planting site. If you have questions regarding application rates, consult the same professionals who conducted the soil test.

Drainage

• Drainage is the other important factor in preparing soil to plant boxwood shrubs. Boxwoods won't thrive in thick or poorly draining soil; their shallow roots will drown and rot in water that doesn't drain away. When preparing the soil, till it to break up any thick clumps. Add 2 to 3 inches of organic drainage aid--such as peat moss, compost or aged manure--to increase drainage. All of these materials will hold moisture and allow excess water to drain deeper into the soil, protecting the boxwood's roots from water damage. Also, never plant your boxwoods in really wet areas, such as near drainage spouts or in the drip-line of a tree or taller shrub.

Mulching

• Because boxwood shrubs have very shallow roots, the roots are susceptible to damage from sudden temperature changes and from strong sunlight. To protect the roots, cover the soil with a 1- to 1 ½-inch-thick layer of organic mulch, such as shredded bark or pine needles. This will also help the soil maintain moisture. Apply this mulch at least 6 inches from the boxwood's trunk, since the material will burn the bark if it touches the plant itself.