Gardening: Beware the early spring forecast

According to a weather map sent to me via Facebook from George Stanley White, retired tree and shrub guru from Wojo’s Greenhouse, Michigan is in line for an early spring. I’m not trained to read weather maps, and because they change from day to day and even hour to hour, I can’t comment on the accuracy of the forecast. However, as the steward of the Stone House Garden at the Rochester OPC, I’m setting up our volunteer calendar accordingly.  

From experience, an early spring means more of the wonky weather we’ve been experiencing for several years. An early spring could mean frost-free weather for a week and then zap, a blast of cold air brings bone-chilling frost, causing damage or death to early spring plantings.

A light freeze, about 32 degrees, will kill tender annuals and vegetables and may cause cosmetic damage to hardy plants, where as a moderate freeze, down to 25 degrees, will destroy hardier perennials and the leaves of many shrubs. A hard freeze of  – 24 degrees and lower will do extensive damage to emerging leaves and flowers of trees, causing loss.

While we can’t do much about the weather, there are some ways to help prevent disaster from a surprise cold snap.

Watering the soil well in the morning may give you a 5-degree buffer, as wet earth retains heat. Do this early in the day, before the temperature drops, and be careful not to wet the leaves because wet surfaces freeze quickly.

Covering tender plants using frost blankets, buckets, baskets or sheets early in the day is another way to protect them. Avoid plastic sheeting and bags because they transport the cold.

Jugs filled with water placed around the garden, close to but not touching the plants, will absorb heat during the day,  and 1-gallon milk jugs painted black work even better. Black absorbs the heat.

This year when spring cleaning the Stone House Garden, we will do the annual beds first and leave the perennial plantings to the last. Their dried stems, leaves and flowers provide insulation that traps warm air around new spring growth.  

At the Stone House Garden, Mother Nature will have her way with established plants and we will do the best we can to protect them. But when it comes to planting tender plants and those that have leafed out in a green house, I continue to use Memorial Day to say, “Gentle gardeners, start your engines and plant.”

  Nancy Szerlag is a master gardener and Metro Detroit freelance writer. Her column appears Fridays in Homestyle. To ask her a question go to Yardener.com and click on Ask Nancy. You can also read her previous columns at detroitnews.com/homestyle.