If the fragrant subshrub is not cut, it will grow taller and taller over the years. In principle, that would not be a problem if the vegetation zone of these shrubs were not almost exclusively in the tip area.
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Lignification in old age
While the plant continues to grow vigorously above and usually tirelessly bears flowers, the branches close to the ground become increasingly lignified and are then no longer able to attach leaves or even flowers. So the shrub is balding from below. At some point the tips of the shoots are so heavy that the branches can no longer hold the weight. The result: the branches lean towards the ground and the beautiful, compact shape is lost. This shrub no longer has much in common with the picturesque sight of lavender fields swaying in the wind.
The most common mistakes when cutting
When pruning lavender, many gardeners make the mistake of not cutting back hard enough. It is recommended that the shrub be cut back a lot. In the case of the two-thirds pruning, the long flower stalks are incorrectly included by inexperienced gardeners, so that the shrub as a whole is far too little pruned. To be sure, cutting too high does not harm the shrub, but it also does not help to keep the plant nice and compact and to prevent it from becoming lignified.
Another fatal mistake when pruning lavender is to prune it back near the ground in spring or autumn. The lavender is not a perennial that needs this radical pruning. If you cut too deep into the wood, the shrub can no longer sprout and dies.
The lavender is actually one of the simplest plants in the garden. Plant, water and then it does not require any care until pruning. Ideally, you cut a lavender twice a year. The gardener should carry out the maintenance pruning for lavender by mid-August at the latest. August is particularly suitable for rejuvenating a lignified lavender bush, because then the wood still has time to sprout again. A later pruning is not advisable, as in this case the new shoots cannot mature and would freeze to death in winter.
- Cut back in spring or in late July / early August
- no later than mid-August
- do not work on hot days or in the midday sun
- preferably on a slightly cloudy, rain-free day
- When it is wet, germs quickly penetrate the wounds
Rejuvenate old lavender properly
If the lavender is not cut at all or only very little cut for a few years, the lignification in the lower area is usually very pronounced and the shrub unsightly. This can happen relatively quickly as lavender grows quite quickly in optimal years. If the plant is over 10 years old and has hardly been pruned, you should approach the rejuvenating pruning with extreme caution, because you run the risk of being damaged and possibly perishing in the case of uncut plants.
In the case of old, heavily lignified lavender bushes, quite a bit of overcoming is necessary to rejuvenate them. However, the approach must not be too radical. Lignified shoots up to the thickness of a pencil are usually not a problem. The rejuvenation cut can take place either in one step or over two years. If the shrub has never been cut, the multi-year procedure is recommended. So that you don’t lose track, first cut off all flower stems (if any) at their roots. If the shrub is very large, it is advisable to evenly shorten all leafy and green shoots (hemispherical shape) before starting the actual rejuvenation cut.
- look for the oldest and thickest branches close to the earth
- Cut off immediately after the first branch
- leave one eye pointing outwards (if visible)
- otherwise leave about 3 cm of shoot at the fork
- never cut off at ground level
- If necessary, close wounds with wood tar
- cut the other branches just above a branch of younger shoots
- Leave a maximum of 3 centimeters of the previous year’s shoots
In the following year, more old branches are cut just above the first branch. If the woody branches that were shortened in the previous year sprout again, these young shoots are cut back to a maximum of 5 to 10 cm in length. Repeat this until all branches are tapered. Brave gardeners can also do the rejuvenation pruning at once. Of course, it can happen that the lavender bush does not sprout again, but it is still worth a try.
Care after cutting
Additional fertilization or intensive watering is not necessary after the lavender has been cut. The Mediterranean shrub is one of the poor eaters and copes well with drought, so that too much irrigation water is rather bad. Large amounts of nutrients make its shoots soft and long. These are not good conditions for a good winter hardiness. Since the shrub lacks the protective foliage after the radical cut, it should be piled up with the cut material or a thick layer of leaves before the first frosts.