Snow and cold temperatures are in the forecast for much of Southern Ontario Tuesday and Wednesday nights. Both ginseng and lavender growers have the option to employ row covers to protect tender plants in the spring. Here are things to think about when planning for these conditions:
Snow – The only impact anticipated from snowfall is the potential to collapse shades if the shade has already be erected. At this time, 5 to 10 cm of snow are in the forecast for Norfolk County, with a little less the further west and north you go. Snow this time of year is often heavy and wet. The potential to collapse shade will depend on how quickly the snow melts as it is accumulating. It is best to stop erecting any more shade until after the snow has passed.
Freeze – Plants in older gardens are emerging out of the soil but are still under the straw. A few plants may be poking through the straw if the straw cover is thin. In most gardens there is enough insulation to prevent injury from the forecasted low of -3C for Norfolk. Covers will help to prevent injury to older gardens where some plants may be exposed due to thin straw.
Snow – There is no potential for injury to lavender from snowfall at this time of year.
Freeze – There has been no research on the sensitivity of lavender to cold temperatures at different growth stages. The best estimates would suggest that most plants would be able to withstand temperatures of at least -5C at this time of year , but it depends on how much new green growth is emerging. Bright green new growth is most at risk. Last year’s cold temperatures in early- to mid-May did not damage new shoots. Temperatures at that time reached -3 to -4C at a time when plants were slightly more advanced than they are now. The current forecast is for temperatures from -3 to -5C Tuesday and Wednesday nights. If tender shoots are killed by freeze, it is likely that new shoots would emerge from the stem over the next few weeks, although the subsequent growth would be a little weaker. If you are concerned about the cold, there is no down side to putting row covers back over the plants if you have the ability. Otherwise, the potential for major damage appears low unless forecasted temperatures continue to trend lower.