Pansies (above) are some of the hardiest spring annuals.
Spring planting can be a bit of a gamble. Understanding a few guidelines will ensure your time and money don’t go to waste.
Average last frost date
Some plants are frost hardy (can survive a frost) while others are too tender. Since we have historical weather records dating back to 1888, we can establish probabilities. Our average last frost is around April 15th. That means there’s a 50-50 chance we’ll see frost after that date. Our “frost free” date (May 14th) is simply the latest frost ever recorded, which was back in 1914. Many gardeners consider Mother’s Day a good time to plant, when the probability of seeing another frost drops below 10%. If you want to learn more, THE CHARTS > from the National Gardening Association.
Annuals
Gardeners typically group flowers into two categories: “cool weather” and “warm weather” based on what weather the plants perform at their best. Options like pansies, stock, snapdragons, alyssum, and ornamental cabbage/kale are great for early spring planting because they can withstand the inevitable frosts. They do have their limits though. If temperatures fall below the upper 20’s, even the cool weather plants will have foliage freeze. A night time cold snap won’t kill the plant roots –the plant will recover, but most gardeners don’t want to wait and opt to re-plant. Cool weather plants also flower best when the temperatures are in the 60’s and low 70’s. Once the heat of summer arrives, the plants will continue to grow, but they’ll flower less. Then, when cooler fall temperatures arrive, they’ll begin to produce more blooms again.
Perennials
Similarly, some perennials are more hardy than others. For example, Hellebore (Lenten Rose) have evergreen leaves and withstand being covered in snow. They’re the first to flower in spring– even before the crocus come up. Creeping phlox, vinca (periwinkle), and heuchera (coral bells) are also good candidates for early spring planting.
Hardening Off
When annuals or perennials are purchased from a greenhouse, the plants are accustomed to the warmer conditions found inside. Once you get them home, it’s best to allow the plants to adjust to cooler temperatures for a several days before planting. Keep them outside during the day but bring them in at night. This process is known as hardening off.
Trees & Shrubs
If a deciduous tree or shrub is still dormant, it’s safe to plant. Once leaves or flowers begin to emerge, it’s best to wait until the danger of freezing temperatures has passed. Evergreen trees or shrubs are safe to plant in early spring.
If a newly-purchased tree or shrub has come out of dormancy, wait to plant it until danger of freezing weather is behind you.
