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Rose Soil


Most rose beds in our area are built as raised beds to ensure proper soil drainage and aeration and, therefore, require some sort of retaining wall to contain the soil and the top dressing of mulch.

 

If you have a sandy or gravel subsoil, you will have no drainage problem and can build beds at ground level with just enough curbing to keep out the grass and hold in a 3 to 4 inch layer of mulch. If your subsoil is limestone rock, caliche or heavy clay (more typical of the Austin area), you must build your bed from 6 to 12 inches above lawn level. You want a soil depth of up to 20 inches (see below) in the bed. The depth to which you are able to excavate will determine how much material you will have to provide to raise the soil level. In other words, if you are able to excavate down 12 inches, you will have to provide materials to raise the soil in your bed an additional 8 inches. Before you begin construction, use a line level or some other method to judge the contour of the land. You want the top surface of the bed to be nearly level in order to keep fertilizer, water and bark mulch located in place, rather than having them washed down to the lowest part of the bed.

 

Good rose soil is a key to growing good roses. Good rose soil contains at least-third organic material. Organic material provides a healthy environment for earthworms and microorganisms which in turn help provide a healthy environment for the roses.

 

New beds are somewhat "fluffy" because of the soil mixing process, and so initially will settle quite a bit. A new rose bed ideally should be completed and filled with soil by December to allow the soil to mellow and settle before planting roses in February or March.

 

The soil should be cultivated to a total depth of 18-20 inches for large roses and a minimum of 12 inches for miniatures. The "old reliable" formula for rose soil is:

  • 1/3 top soil (or original soil, if it is good quality garden soil),

  • 1/3 or less, coarse sand, and

  • 1/3 or more, organic matter (compost, peat moss, decomposed manure, cedar flakes, etc.).

     

    For the typical rose bed of 100 square feet you will need about 2~1/4 cubic yards each of top soil, sand and organic material.

     

    To mix the soil for your rose bed, first excavate your bed to the required depth. If the existing soil is caliche or heavy clay, discard it. Assemble the material you are using for the raised bed (landscape timbers, stone, etc.). Then put a layer of the three basic ingredients (top soil, sand and organic matter) in your bed and thoroughly mix. Add another layer and thoroughly mix again.

     

    In the top 6 to 8 inches of soil (for a 100 sq. ft. bed), thoroughly mix in the following:

  • 5-10 pounds of gypsum

  • 4 pounds of agricultural sulphur granules (or sulphur-iron compound)

     

    These ingredients will provide initial nutrients for the new plants and also will improve the condition of clay and alkaline soils. The final soil mixture should crumble in the hand easily--it should not stick together in a ball when squeezed. This soil will be loose enough to allow water and oxygen penetration, yet heavy enough to anchor the root system.

     

    If your budget allows, you can use pre-mixed "garden soil" purchased from a soil supplier. Be sure to ask about the composition of the soil. Look for a soil mixture that contains 30% to 40% compost. Buy your soil from a reputable dealer.

     

    Fill the rose bed until the center of the bed forms a crown 4 to 6 inches higher than the edges to allow for settling.

     

    NOTE: The soil level at the edges should not be level with the top of your curb. You don't want the soil to wash out of the bed, and you need to leave 4 inches so you can cover the soil with mulch after planting roses. Water your mellowing rose bed thoroughly every week if there is no rain.

     

    Over time, roses will deplete the organic matter in the soil. A rose bed is not like a vegetable garden where you can till in new organic material each year. You must add organic material to the soil surface and let it work its way to the root zone over time. Add 3-4 inches of compost as mulch 3 times per year to keep up the organic content of your soil. If the compost you add is very light in texture, cover with an inch of pine bark mulch so the compost won't be washed away. January, May and September are good months to add compost to your beds.