Answer: Grass clippings aren't the best material for mulching. They have a tendency to mat, nullifying the air cushion effect that makes a mulch so effective in moderating soil temps and moisture retention. They also occasionally rot, to the point of being a little uncomfortable to the nose. And thirdly, some grass clippings contain the residues of herbicides and pesticides often used in lawn treatment products. Roses aren't that fussy about the pH of the soil, although extremely acid or alkaline (basic) soils may lead to nutrient imbalances. They do best, however, in soils on the heavy side (some varieties such as Rugosa hybrids do prefer the sandy type).
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