A well-prepared bed is essential if rose bushes are to produce beautiful blooms season after season. The bed needs to be located correctly--in a spot that receives at least 6 hours of sun per day--and be large enough to accommodate the number of bushes you want to plant (allow at least 24 inches between bushes). The most important step is creating a nutrient-rich soil that is built for long-term use.
Test the drainage properties of the soil in your desired location. Dig a hole 18 inches deep and fill with water. If the hole is empty in 6 hours, drainage is sufficient. If not, build a raised bed (Step 2) or add organic matter (see Step 3).
Create a raised bed by tilling the designated area, enclosing in a frame and filling with 6 to 8 inches of rich, well-draining soil. A rich soil mix combines two parts organic matter, such as composted pine bark or peat moss, and three parts soil. The frame may be constructed from railroad ties or wood beams that will not easily decompose, such as redwood or cedar, laid on the ground and on top of each other until the desired height is reached.
Add 4 inches of organic matter, such as pine bark compost or peat moss, to the topsoil and cultivate to a depth of 12 inches across the bed. Organic matter improves soil drainage and provides nutrients to roses over time. Dig out dead roots and rocks at this time to aid drainage and soil aeration.
Conduct a pH test on the bedding soil with a home kit or send a sample to a local university extension office (most will do the test for a small fee). A pH range of 5.5 to 6.5 is optimum for roses. If the soil is more acidic than that, amending the soil with lime may be needed. In some cases, more than a year may be required for pH adjustments to take effect in the soil. Because there are so many different amendments and each one is specific to geographic locations and soil type, consult the local extension experts for tips tailored to your needs.
Incorporate superphosphate at the rate suggested by the fertilizer manufacturer. Blend well with prepared soil to provide food for bedded roses over a long period of time; roses respond well when given slow-release additives and fertilizers.