When spring arrives on the High Desert the days of minus 24 degree temperatures on December 8th and 9th will long be forgotten. But when late April and May rolls around you will see what those very cold temperatures did to your gardens.
When the temperatures get this low I notice damage on evergreen shrubs, rhododendrons and any newly planted species that had NOT been climatized to our area. A browning or scorched leaf tip on evergreen foliage in early spring is a form of winter injury. Browning usually occurs from the needle tips downward. Winter burn is usually attributed to loss of water through leaf transpiration. Winter sun and winds dry needles. Water in the stems and roots is frozen and unavailable to replenish loss. A rapid drop in temperature after a sunny day can also cause further injury to the plant..
Another form of winter damage is "Frost Cracks". Frost cracks, sometimes called freeze cracks, appear as shallow to deep longitudinal cracks in the trunk of trees. Frost cracks occur on the south or southwest side of trees, following a sudden exposure to direct sun. In winter, the temperatures on the sun-side of the trunk may exceed air temperatures by as much as 20 degrees F. This is thought to trigger de-acclimation of trunk tissue. The bark slowly darkens, turns reddish brown and becomes rough. After a time, the callus tissue eventually cracks and falls away. Sometimes only the outermost cambium layer is damaged and a sunken area appears on the trunk. Affected trees often have sparse foliage, stem dieback and stunted growth.
Root damage to perennials can cause spring plant kill. Root tissues do not acclimate to temperatures much below freezing and can be killed or severely injured by soil temperatures below 15 degrees F. This is especially true for shallow rooted plants. Fortunately, if you mulched as I have always recommended, your damage should be far less than those not mulched. Plants with frozen roots may wilt and decline after growth resumes in the spring.
Salts used for deicing sidewalks and driveways can cause damage to trees and shrubs. Symptoms of salt damage appear in spring and early summer and include browning of evergreens, leaf scorch, branch die back and dead areas in turf.
When spring arrives be on the look out for any of the above mentioned problems that low winter temperatures can cause.
When the temperatures get this low I notice damage on evergreen shrubs, rhododendrons and any newly planted species that had NOT been climatized to our area. A browning or scorched leaf tip on evergreen foliage in early spring is a form of winter injury. Browning usually occurs from the needle tips downward. Winter burn is usually attributed to loss of water through leaf transpiration. Winter sun and winds dry needles. Water in the stems and roots is frozen and unavailable to replenish loss. A rapid drop in temperature after a sunny day can also cause further injury to the plant..
Another form of winter damage is "Frost Cracks". Frost cracks, sometimes called freeze cracks, appear as shallow to deep longitudinal cracks in the trunk of trees. Frost cracks occur on the south or southwest side of trees, following a sudden exposure to direct sun. In winter, the temperatures on the sun-side of the trunk may exceed air temperatures by as much as 20 degrees F. This is thought to trigger de-acclimation of trunk tissue. The bark slowly darkens, turns reddish brown and becomes rough. After a time, the callus tissue eventually cracks and falls away. Sometimes only the outermost cambium layer is damaged and a sunken area appears on the trunk. Affected trees often have sparse foliage, stem dieback and stunted growth.
Root damage to perennials can cause spring plant kill. Root tissues do not acclimate to temperatures much below freezing and can be killed or severely injured by soil temperatures below 15 degrees F. This is especially true for shallow rooted plants. Fortunately, if you mulched as I have always recommended, your damage should be far less than those not mulched. Plants with frozen roots may wilt and decline after growth resumes in the spring.
Salts used for deicing sidewalks and driveways can cause damage to trees and shrubs. Symptoms of salt damage appear in spring and early summer and include browning of evergreens, leaf scorch, branch die back and dead areas in turf.
When spring arrives be on the look out for any of the above mentioned problems that low winter temperatures can cause.
2 comments:
LInda, I have noticed a lot of brown needles on some of my pine trees. Is this also due to the extremely cold temperatures we had?
Too early to tell. Damage from the sub zero weather won't show up until late April. If the needles are browning from the inside out, then this is a normal browning. If they are browning from the outside in, then there is either a disease or bug problem.
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