What plant hardiness zone is Royal Oak
Royal Oak is located at Oakland County, Michigan (MI), USA.
Plant hardiness zone (winter frost zone or gardening zone) for Royal Oak is 6a by the USDA scale.
Coldest zone's winter temperature is −10 … -5 °F.
Plants of 6a USDA hardiness zone suitable for outdoor gardening and growing in this winter frost zone 6a USDA.
Royal Oak, Michigan @ wikipedia.