Between the early frosts which surprise the gardener in autumn and even more so the late frosts which sometimes rage until mid-May, the shrubs are put to the test. In some years, cold spells can be particularly severe when they are no longer expected. Admittedly, spring frosts are the fear of gardeners who, when they see the damage caused, do not always know what to do. Here are some tips to follow.
Main damage caused by frost on shrubs
Generally, it is the aerial parts that suffer first from the ravages of frost. Depending on the season, we can see that the leaves are affected, the buds, the branches or even the flowers. All these organs have literally been burnt by frost since they were not protected. One can for example deplore at the level of the leaves, a softening, a blackening, and at the level of the stems, a browning at the ends which will be followed by their drying out.
Shrubs can pay a heavy price for these weather episodes that the gardener would do without. Catalpa, Hydrangea, Wisteria, Japanese Maple, Kiwi, Magnolia and many other shrubby plants suddenly give the garden an air of desolation.
Be patient with partially frozen shrubs
After a devastating frost, many novice gardeners are tempted to immediately prune all the affected parts of their shrubs. However, it is on the contrary recommended to do not rush to perform a pruning. The key word is “observation”. Indeed, we must wait to see if the shrubs show some signs of recovery.
Moreover, if the risk of frost is still to be feared, the damaged parts are left in place for as long as necessary because they constitute protection for the shrub.
In shrubs, plants with a amazing ability to recover from a good frost, we quickly notice the appearance of new buds. This is a good sign! We can then move on to the removal of the necrotic parts. But sometimes it is necessary to wait until summer to finally see a shrub reborn which appeared to be dead after freezing. As long as it looks like an old carcass with no apparent life but the summer hasn’t passed, we don’t tear it up because nature has many surprises in store for us (and good ones!).
Prevent cryptogamic attacks on frozen shrubs
As soon as frost has caused damage to the shrubs, it is prudent to protect them against the risk of fungal diseases and any bacterial blooms as damage from severe frost is likely to be aggravated.
To do this, it is enough to spray the shrubs with Bordeaux mixture, as is done with many plants that have suffered a hailstorm. Bordeaux mixture prevents, among other things, moniliosis, canker, and heals wounds.
Perform custom pruning for evergreen shrubs that have frozen
A late frost that rages for several days in a row can damage evergreen shrubs. All is not lost of course, and it is by a specific pruning that we will be able to help them to start growing again.
- Severely reduce the evergreen ceanothe whose branches are burned, without fear for its next flowering since this beautiful shrub only flowers on the wood of the year.
- Fold back only the blackened stems of the Laurier-rose and above all do not touch those that have not suffered from the frost. Branches damaged by the cold can be lowered to 15 cm from the ground without any problem. The shrub will come back without any difficulty thanks to its great vigour.
- Manually remove burnt leaves from the stubble of the Bamboo a little too exposed to the icy wind. New leaves will grow back.
- Prune the ends of branches with pruning shears when frost has caused browning or drying out of the Photenia and the Laurier tin.
- Do not prune the Mimosa frozen before summer. It has every chance of recovering on its own because its stump has certainly not been affected by the frost.
These are only a few examples, but overall it can be noted that the gardener should not lament after a heavy late frost because the ornamental shrubs will produce new shoots on dormant buds. He can simply remove the blackened ends of the branches and the roasted leaves.
As to fruit bushes, they will not be productive if they have frozen at the buds, and little can be done for them until fall. This will be the time to carry out a severe pruning of all the young wood that has grown since spring, as the shrub can no longer produce fruit for the moment. To describe this situation, gardeners say that the shrub makes wood. But there is nothing to worry about, the fruit harvest will be abundant the following year.
Plan ahead to protect your shrubs against frost
In the garden as elsewhere, prevention is better than cure. We know very well that each year, the frost does not only rage in winter and can be virulent to the Ice Saints who “return” every year on May 11, 12 and 13. Shrubs are protected with winter sails and one thick mulch at their base to insulate the roots as much as possible from the cold. Finally, there is no point in rushing: in regions where we are used to suffering late frosts, we differs planting chilly shrubs because they are particularly sensitive to heavy frost.