Previous articles on this blog have focused on the best methods of pruning in a typical year. With the winter damage this year, pruning techniques may need to be modified to get plants back to a rounded shape. To complicate pruning, many damaged plants are sending up new flower stalks, resulting in a late and staggered harvest. Here are some thoughts on pruning affected plants:
Many older lavandins have still not recovered from winter damage. Often only a few branches have grown back with no new growth from the base. These plants will likely never recover a rounded shape, and should be removed and replaced with new plants. Take the opportunity to collect cuttings from these plants. Any plants with new growth from the base should be pruned aggressively at this time if they have not been pruned already. Aggressive pruning of the older growth will encourage the new growth. This probably means cutting the plants back to a few centimetres below last year’s growth, unless the new vegetative growth has already grown well beyond last year’s growth. In this case, remove enough growth to result in a relatively firm rounded mound, bearing in mind that new growth will not be as firm as in a typical year.
In most cases the angustifolia (English) cultivars sprouted substantial new growth from the base of the plant. Yield during the main flowering period this year was low, but flowers continue to develop on the new growth. Healthier plants should be pruned as normal, with about one third to one half of the green tissue removed. Plants with minimal older growth and mainly new growth from the base should be pruned more aggressively to remove the dead woody tissue and allow the new growth to become stronger and more dominant on the plant. This means pruning a few centimetres of the woody growth out and the top of the vegetative growth along with it. Plants in between these two extremes should be pruned more aggressively than healthy plants but not deep enough to get into the woody part of the healthy stems.
There is the temptation to allow all of the flowers to develop on the new growth to make up for lost yield in July. However, this could delay the recovery of the plants and result in weaker growth going into the winter. This may result in additional winter kill. Consider allowing only a few rows to develop flower development if you need additional flower material. Fertilizing is also a good idea at this time of year to help the plants recover, but should not be done beyond August, or the plant may be too vegetative going into the winter. Consider a small application of nitrogen (e.g. 25 kg/ha) as a sidedress along each side of the row.