There are many methods gardeners in colder climates use to tell when winter has passed and it is safe for planting spring gardens. Some use the stars, others the moon and some simply depend upon their local weather forecaster. While each of these methods can be useful, the most practical and accurate means of telling when it is safe for planting flowers is to simply observe nature's actions.
Leaf Buds on Trees
Seasoned, established trees have weathered many winters. Their roots are buried deep into the soil and their trunks are thick from years of storing up winter nutrients. These experienced plants will not waste their precious energy sprouting leaves unless it is certain that winter has passed. Before planting anything in your garden, go outside and take a look at the trees, if they have leaf buds forming, then it is a sign that it is safe to plant.
Frost Danger Has Passed
Groundhog Day is a fun holiday with a great deal of superstition attached to it, but the principle behind it does make sense. One of the best signs for planting a spring garden is being certain that any danger of frost has completely passed. This information can be obtained directly from observing outdoor temperatures over the course of a week or through county records of the previous year's final freeze date. If you are depending solely on this approach, be sure to account for weather anomalies such as El Nino.
Wild Flowers Are Forming
The snow is melting on the ground and patches of earth are revealing themselves. Over the next two weeks, watch the ground for wild flowers. Another of the best signs for planting spring flowers is that spring wild flowers are emerging. Wild flower's wintered seeds have been stratifying all winter and with warm enough weather, form a root and emerge. This weather is without a doubt warm enough for planting a spring garden.