The garden is quiet in winter, but with its low temperatures, it can cause a lot of damage. Plants, trees and shrubs suffer from this, and the phenomenon of frost drought is particularly insidious.

In a nutshell

  • also known as winter drought
  • Plants literally die of thirst
  • evergreen plants are particularly endangered
  • Leaves and needle change color

Endangered Plants

The phenomenon of frost drought is that the plants do not simply freeze to death over the winter, but die of thirst. This frost damage is also known as winter drought. It is certainly a bit difficult to understand that garden plants dry up in winter. It does not affect all plants either, because only evergreen shrubs, trees and other plants are particularly at risk

  • Yew (Taxus baccata)
  • Tree of Life (Thuja)
  • Juniper (Juniperus)
  • False cypress (Chamaecyparis)
  • Cedar (Cedrus)
  • pine (pinus)
  • Fir (Abies)
  • Spruce (Picea)
  • Rhododendron (Rhododendron)
  • evergreen viburnum (Vibirnum) species
  • Photinia
  • Rock Medlar (Cotoneaster)
  • Barberry (Berberis)
  • Spindle shrub (Euconymus)
  • Ivy (Hedera helix)
  • Cherry laurel (Prunus laurocerasus)
  • Boxwood (Buxus sempervirens)
  • Holly (Ilex)
  • hardy palm trees (Arecaceae)
  • Elf Flowers (Epimedium)
Rhododendron Leaves

Notice: Some plants have already developed various protective mechanisms here. For example, the rhododendron and the cherry laurel roll up their leaves to reduce evaporation.

What is happening?

The leaves of the evergreen plants perspire even when the temperature is below zero during the cold season. A lot of water is lost in the process. This moisture would then normally have to be absorbed from the soil again via the roots. However, problems can arise here, because at very low ground temperatures, i.e. minus degrees, the water is bound there as ice crystals. But not only the ground and the water are frozen, but also the plant roots. They are then no longer able to absorb and transport water and nutrients to compensate for the transpiration loss of the leaves. It gets particularly bad when the first rays of sunshine come out in late winter, which increases water evaporation through the leaves enormously. There are normally two different types of frost drought.

Complete cessation of water supply

  • rapid opening of the stomata (stomata) on the underside of the epidermis
  • Openings are used for gas exchange
  • thereby increased transpiration of water
  • Replenishment from ground not possible
  • so no supply of the plant parts with water

Development of chronic damage

  • Stomach openings remain closed
  • Water release through cuticle (waxy layer over shoots and leaves)
  • endangered plants coniferous and deciduous trees

The consequences of frost drought can be particularly bad for phanerophytes, especially when there are dead frosts or when the plants are in places where there is little snow. These are plants with woody, above-ground plant parts that overwinter in renewal buds.

Occurring Symptoms

The symptoms of frost drought are not much different from symptoms that appear when a plant suffers from a lack of water:

  • brown spots on leaves
  • initially drooping leaves
  • later withered leaves
  • get stuck on tree/shrub
  • brown needles in conifers
  • brown colored shoots
  • partial death of shoots
Brown needles on fir (Abies)

The complete damage to the plant only becomes apparent in the spring. Affected growths do not always die. Watering can be a quick help here and a strong pruning should also be done. This can stimulate renewed sprouting. However, this requires some patience. Because it may be that the first new shoots only appear late in June or July. However, if the plant does not show any changes after months and looks completely brown and dry, the only thing left to do is clear and dispose of the plants.

preventive measures

Sufficient watering throughout the year can help to protect particularly endangered plants from a winter drought. In addition, there are various measures that contribute to protection:

  • Water evergreen plants on frost-free days
  • Ground must not be frozen
  • otherwise no water absorption possible
  • don't water too much at once
  • preferably more regularly, weather permitting
  • Avoid waterlogging
  • pay particular attention to this with potted plants
  • otherwise plant pots can shatter due to expanding water
  • Always check the soil surface for moisture first
  • Application of a mulch layer of compost, leaves or chaff
  • additionally cover the root disc generously with:
  • Twigs, jute sacks, light-colored synthetic fleece, sheep fleece, willow, thatched or reed mats
  • do not use dark fleece as it reflects the sun

Alternatively, potted plants or sensitive evergreen shrubs and trees can be completely wrapped in a light-colored fleece or jute sack. They are protected from the rays of the winter sun and the transpiration of the leaves is reduced.

Note: Ample watering in the fall through October/November can also be helpful. The soil should be well moistened. 30 to 40 liters of water per square meter is appropriate.

frequently asked Questions

What exactly is meant by frost?

A frosty day is already spoken of when the air temperature at a height of two meters falls below 0 °C for a period of time. Even at air temperatures of around 2 to 4 °C, frost (ground frost) can prevail directly on the ground, i.e. the temperatures here are below the freezing point. This is because the heavy air descends to the ground from top to bottom. In general, all water freezes during frost.

Can frost drought be confused with normal plant frostbite?

Yes, absolutely. The plants show similar symptoms with both types of frost damage. If a plant freezes, all of its cells are destroyed by ice crystals. Affected plants can then no longer carry out the metabolism. As a result, just like with frost drought, wilted and brown leaves appear. However, they get a little mushy.

Can perennials also suffer from a winter drought?

As a rule, the parts of the plants above the ground die off in late autumn in most flower perennials. Usually they are then cut off a hand's breadth above the ground. Such perennials are considered deciduous and do not suffer from a winter drought. The situation is different with evergreen perennials such as the elf flower or biennial flowers such as wallflowers, horned violets or pansies. Here should be a protection against the winter drought.

Category:

Garden plants