Answer: Unfortunately I don't think there is anything you can do. I think you are seeing the effects of microclimate causing your plants to bloom a little bit later than the others. For example, this could be they are planted in a location that is maybe a little bit shadier. Or it might be in a frost pocket, a low lying spot where frost collects, so there is frost later and the soil stays cooler longer in the spring. Or, maybe you are in a more exposed and windy area and they are in a sheltered area in town with lots of buildings nearby to hold the heat and block the wind. These types of locations can make a big difference to plants.
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