Michigan has a wide range of United States Department of Agriculture (USDA) Hardiness Zones. There are small sections of Hardiness Zone 6 in the south central region, and there are zones as cold as USDA Hardiness Zone 3b in the Upper Peninsula. Temperatures in the warmer parts of the state may not drop below 5 degrees below zero F, while temperatures in parts of the Upper Peninsula may reach 35 degrees below zero F. When planting perennials, make sure they are cold-hardy for your part of Michigan. When planting annuals, be aware that colder parts of the state may have later hard frosts than warmer parts.
Prepare the soil after the risk of hard frost has passed. The exact date will depend on the year and on the part of the state in which you will be planting. Consult a Hardiness Zone map to know what zone you're planting in, and consult your local county agricultural extension if you are overly concerned about a late frost.
Dig the soil to a depth of 8 to 12 inches and turn the soil.
Break up clumps in the soil until the largest clumps are about the size of a pea.
Remove your young flower plants from their nursery pots. Some nurseries sell their young plants in peat pots. If yours are in peat pots, you do not need to remove them from the pot. Plant the entire peat pot in the garden.
Dig a hole large enough to accommodate the plant and place the plant in the hole.
Cover the roots.
Water your newly planted flowers thoroughly.