Spring has sprung and it is once again time to think about removing row covers. Some years it has been necessary to remove row covers in mid-March in areas further south. This year, March has been a bit cooler than normal with a big snowfall in early March in most areas that would have prevented much heating by the sun. It has also been cloudy in many of the milder days. As a result, we did not have as much risk of it warming up under the covers and causing loss of hardiness in the lavender plants. Now that the risk of severe cold has likely passed, it is time to consider removing the covers in all areas.
The longer you wait to remove the covers, the more likely the plants will start sprouting prematurely. This can cause them to be more prone to damage to freezes later in the spring. The sun is getting higher in the sky every day. On a sunny and calm day, temperatures under the cover could be up to 10°C warmer than the actual air temperature, especially with black plastic mulch under the cover. The risk is lower for thicker covers that block more of the sun. However, there is a risk of mould developing on the foliage of the plants with thicker covers, because they also block air flow through the cover.
Other than removing the covers, there is nothing else to be done with lavender plants at this time. The extent of any winter kill will not be known for about month, so it is too early to determine how much spring pruning should be done. I just removed the winter cover from my lavender trial and early indications are the plants are in excellent condition with no signs of winter kill and mostly green foliage. However, plants can sometimes lose the green colour once the cover is removed, only to reappear with the new growth in May. Given the mild winter we just experienced, any significant winter kill that occurs would likely be related to excess soil moisture rather than air temperatures. Spring is a good time to assess your fields for drainage issues and correct them before establishing any new plants.