Answer: According to your zip code you are gardening in zone 5A, the coldest part of zone 5. Depending on the microclimate where you garden, it may actually be as cold as zone 4. This means your butterfly bush may not be winter hardy for you. To try to save it you would need to mulch heavily over the root area in late fall. For the roses, assuming the varieties you have are considered hardy for your zone, you would still want to mulch heavily over the root area. If they are grafted tea roses however you will need to mound soil up over the base of the plant to a depth of about a foot or so. This is necessary to protect the graft and should be applied in late fall, then gradually removed in the spring. You might be able to rake the stones aside and mulch or mound the soil, then replace the stones in the spring. Or, you might consider switching to an organic mulch around your plants as this is more beneficial for the soil in the long run.
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