Crop Update
Lavender is beginning to green up in Southern Ontario. Since temperatures in the winter of 2024/25 were more normal compared to the last several mild winters, expect more winterkill this year. Older plants, especially lavandins, tend to have the worst winterkill based on the temperature. Expect some dieback of older lavandins that have not faced harsh winter conditions over the past few years.
The incredible snow cover in some areas this winter could also have had some effects. Generally, deep snow cover is a good thing because it insulates plants from dry winter winds. However, we have not experienced the amounts of snow that some areas reported since the lavender industry began, so the effects of that much snow are unknown. Any damage that occurred would be due to snow melt in the spring and a flooded root system, rather than any effects of the cold directly. It appears that there was not much frost in the ground under all of that snow, so excess water could still drain away. Winterkill due to a flooded root system will affect any age or type of lavender, often killing entire plants rather than only the tops of the plants.
With the green up beginning, you may be able to do a quick scan of the potential for damage, but it is probably too early to know the extent of any damage. Sometimes the leaves can die over the winter, but the branches can still be alive. New buds can emerge from the stem after a week or two. An early sign of more extensive dieback is if all the leaves on a main branch have dried up, and snapping the smaller branches in half does not reveal any green tissue. Healthy branches should bend rather than snap cleanly. It is best to wait a week or two before doing any extensive pruning of damaged tissues.
In the cultivar demonstration plot at Simcoe, there are 44 cultivars of angustifolia and lavandin. The plot was covered in Agryl P-40 row cover over the winter. A scan shows that most of the angustifolia overwintered well with the exception of a few plants and cultivars that had a root or stem disease issue last year (cause unknown) and those with a prolific second bloom in the fall (e.g., ‘Super Blue’ and ‘Buena Vista’). This is not unusual for cultivars with a second bloom.
There are early signs of more significant dieback in some of the lavandins. The most affected appear to be ‘Phenomenal’, ‘Grosso’, and ‘Impress Purple’ (Figure 1). Other cultivars have more variable damage, with at least some plants without any significant damage. It is unknown if these are true cultivar differences or potentially their location within the plot, since the row cover had a few holes.
Figure 1. Comparison of dead (left) and healthy (right) branches of a ‘Phenomenal’ plant with significant damage to >50% of the plant based on an early assessment.
Reminder: Lavender Module of Ontario Crop IPM
Now is a good time to prepare for pest scouting in your crop this summer. We have minimal products registered for use on lavender, and these are more effective if they are applied at the right stage and before pest issues get out of hand. The pests can have a major effect on lavender under the right conditions, including four-lined plant bug, garden fleahopper, Phytophthora root rot, alfalfa mosaic virus, and Septoria leaf spot. Ontario Crop IPM provides a wealth of information for growers on the biology, identification, scouting, and management of insects, diseases, and disorders of numerous different crops. The Lavender module was launched last year and can be viewed here.
