Answer: I'm an advocate of using organic matter as mulch material. As it decomposes it provides nutrients, and it can be turned into the soil at the end of the season. The pebbles you mention will help suppress weeds and deter snails and slugs, but the pebbles will heat up in the summer sunshine and could radiate enough heat to harm the leaves and crowns of the strawberry plants. An impenetrable mulch such as rocks will certainly keep strawberry runners from rooting, but it would be kinder just to keep the runners clipped off. If they can't root they'll wither and die (not a pretty picture!), all the while using up energy from the parent plant. Strawberry beds should be renovated every 3-4 years and the runners that root can serve as new strawberry stock when it's time to rogue out the old plants.
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