It is that time of year again for cold mornings and possible frost damage. This is a little information regarding frost damage.
Causes of frost damage
Ground frost occurs when the temperature of the ground falls below freezing point (32ºF) and air frost occurs when the temperature of the air falls below freezing point (32°F).
Plant cells can be damaged or even destroyed by frost. Repeated freezing and thawing, or very rapid thawing can be particularly damaging to plants.
Once the temperature has fallen below freezing, a strong wind can make a frost more damaging. Cold winds remove moisture from evergreen foliage more quickly than it can be replenished by the roots; this can cause leaf browning, particularly at the tips and margins.
Newly planted, young plants can be more susceptible to frost damage than fully established specimens.
Plants that are susceptible in Southern California
1. Grass shows frost damage by turning from green to an almost yellow like color.
2. Lantana will lose foliage and become more and more woody each year from frost.
3. Bougainvillea can be severally damaged.
4. Agapanthus just does not like the cold.
Most plants don’t like frost but some just suffer more!
Sometimes frost damage is apparent almost immediately following freezing. However, this is not always the case and with some plants, particularly woody ones, the damage may take several months to appear. Look out for the following signs:
• Tender young growth may be damaged by spring frosts, causing scorching and pale brown patches to appear between the leaf veins.
• Hard frost in winter can cause the leaves of hardy evergreen plants to be scorched and turn brown, and may eventually lead to the death of the plant, i.e. Pittosporum.
• The foliage of certain plants exhibiting early symptoms of frost damage appears water-soaked and dark-green, turning black in time.
Prevention of damage
• Mulching with a thick layer of organic matter around the plant material prevents the ground becoming frozen providing a level of protection.
• Choose plants that are reliably hardy and suited to your growing conditions.
• Select planting positions carefully to avoid ‘frost pockets’.
• Plants exposed to early morning sun may thaw too rapidly after a frost, causing damage to flowers and young growth. Many flowers can be ruined by a single frost.
Important: Do not automatically give up on a plant that has been frost damaged. Many plants can be surprisingly resilient and may well rejuvenate from dormant buds at or below soil level. This takes time, so recovery may not be seen until early summer. Consider leaving the damaged plant in the ground until mid-summer. If no re-growth has appeared by then, replace the plant.
If you have any questions, you may contact Sundance’s landscape and architectural specialist, Jerry Provansal at