Viking Mom what are frost dates?
The frost dates are a guide to help Farmers and Gardeners know when to plant. There are plants that thrive in cool weather while others thrive in warmer weather which is why it is important to know when to plant. In Southern Californa we have to watch for heat index as well.
Viking Mom, how do you know when to plant?
The key factor is knowing your plants. It doesn't matter if it is produce, vegetables, herbs or ornamental. Knowing the plant will determine when to plant or if your region is a good place to grow. Knowing when your regions average last spring frost date will also aide in your decisions making.
You can read more here at Mother Earth News
Another place to look for frost dates is on the back of the seed packets and labels.
Sometimes it won't say "Frost Date" but it will say what the temperature should be for the soil. This is always important to know.