Issue: May 5, 1997

Ash tree leaves frozen

My ash tree had already formed leaves before the most recent severe weather. The leaves froze, turned black, and fell off. Will it die?

Your tree will probably not die, but it may be late in developing new leaves and needs to be well cared for this year. You may, in fact, continue to see twig and branch dieback for several years following this year's spring freeze injury.

Since the buds had broken and leaves were formed, you may have had total death of the new growth and associated buds. However, trees often have an insurance policy in the form of accessory buds. These are smaller buds adjacent to the primary bud which suffered the damage. These accessory buds rarely grow and produce branches unless something happens to the primary bud. This is what happens when you prune off a one-year-old branch and a new growth develops at the base of the removed branch. This bud may also grow if the primary bud or branch is killed by insects, disease, wind, or cold weather.

Later, as the accessory buds begin to grow, you will get a better idea of the extent of the damage. You may see growth beginning near the end of the twigs and branches in the tree if damage was minimal. If damage was severe, you will observe considerable dieback as the new growth begins farther down the branches leaving a foot or more of dead branch. Remove the dead branches by pruning after you have observed good development of new twigs and leaves. Be sure the tree receives adequate water this year, but do not apply heavy fertilizer applications. If the tree is healthy, it will contain sufficient food and nutrient reserves to produce the new growth. Light fertilization after the growth has formed will be sufficient if any fertilization is necessary.

Trees which were not healthy, suffering heavy insect infestation, stressed by the previous few years' drought, stressed by poor culture and compacted soil, injured by herbicides, or newly planted may be sufficiently injured to cause death. These trees may attempt new growth but fail to sustain this growth. This will be especially true if the cambium were injured. The cambium is the layer of dividing cells under the bark which forms new xylem and phloem each year. Xylem and phloem carry water and nutrients from the soil up (xylem) and sugars and amino acids down (phloem) through branches and the trunk. If the cambium were sufficiently injured to prevent adequate formation of phloem, the roots would starve as they could not receive adequate food from the leaves. Once the roots die or are injured, the top would begin to show symptoms.

Trees injured by any stress, including stress from spring freezes, become more attractive to insects. In fact, injured trees produce chemicals which attract the insects that will feed on and kill injured trees. Dead and injured portions of trees may also be more prone to fungal attack. So, be observant looking for insect and disease problems in your injured trees.

Remember, not all insects or diseases are cause for concern, but even some which might not otherwise be a problem should be watched closely. If you see insect populations or disease symptoms, determine what insect or disease is present and then you may safely decide if control measures are warranted. Your local County Extension Service can help you make these determinations. If control measures are necessary, be sure to use products labeled for controlling the identified problem and for use on the specific trees you will be treating. Read and follow all label directions to maximize safety and effectiveness.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!