How to protect and restore plants after an unexpected freeze



The 2022 holiday season in the southern and southeastern United States has blown up with a storm that won’t soon be forgotten. Our area didn’t get much of the snowfall that wreaked havoc in the Midwest and Northeast. However, the wind and cold temperatures packed a punch for our power grids and landscape over a long period of time. We now find ourselves entering 2023 with many questions about the extent of the damage and the next steps for our lawns and landscapes. Before we get to the practical steps, let’s review recent events and learn how to revive plants after an unexpected freeze.

What’s the difference between a minor cold spell and a major freeze event?

The weather event that just hit the south brought a 40°F drop over much of our area from the evening of December 22nd into the next morning. For many, this rapid fall was accompanied by strong winds and temperatures below 15°F for at least 32 hours. Shockingly, most places didn’t rise above 32°F over 80 hours. This combination of circumstances creates major problems. Freezing damage in plants is mostly the result of ice forming inside the plant that punctures the cell walls, and temperatures throughout the region were extreme enough for this to occur. Furthermore, rapid defoliation meant that plants were not able to implement internal defense measures to withstand low temperature stress. Wind also contributes to desiccation (drying), which can damage plants.

What types of plants are susceptible, and what does the damage look like?

The damage caused by this type of cold weather is extensive. Most warm-season turf grasses, such as zoysia grass and bermuda grass, had already gone into winter dormancy before this event, so signs of damage will not show until warmer weather in the spring. Injury is now quite visible on cool-season grasses, with leaves that are normally green having brown, necrotic tissue.

Many conifers are now showing golden or brown discoloration, but we won’t know the extent of the injury for a few more months. Low temperatures can be particularly harmful to landscape plants such as:

  • Camellia (Camellia spp. and cvs., zones 5–9).
  • Akuba (Akuba spp and cvs., zones 6b–9).

Aucuba with winter loss

  • Distillium (Distillium spp and cvs., zones 7-9).
  • Holi (Ilex spp and cvs., zones 3–9).
  • Indian Hawthorn (Rhaphiolepis spp and cvs., zones 7-9).
  • Arizona cypress (Cupressus arizonica(zones 7-9)
  • Osmanthus (Osmanthus spp and cvs., zones 8b-11).

Variable osmanthus with freeze damage

  • Chinese fringe flower (Luropetalum Chinese(zones 7-11)
  • fig (fix spp and cvs., zones 6b–9).

Hardy plants of concern include:

  • Japanese cedar (Cryptomeria spp. and cvs., zones 5–9).
  • Cherry Laurel (Pronus laurocerasus(zones 6-9)

Cherry laurel with colorful dried leaves

Hinoki cypress with winter damage

  • Boxwood (Boxus spp. and cvs., zones 5–9).

Boxwood after an unexpected freeze

  • sweet box (Sarcoccus spp. and cvs., zones 6–9).

Sweet box with colorful plants

A close inspection of some plants may reveal that the bark is split, cracked, or peeling from the stem. Because it disrupts the plant’s ability to move water from the roots to the leaves, plants with this type of damage are not expected to recover quickly, if at all. Spring may show that some woody species, such as crape myrtle (Lagerstroemia indica, zones 6-9), are killed to the ground or killed outright by warm-season grasses, tender perennials, and even “borderline” woody plants. Rapid temperature changes, fall severity, and duration of lethal temperature exposure can be tripled. Only time will tell the full extent of this winter phenomenon.

Can I revive plants damaged by severe winter weather?

Spring seems far away, and you may be wondering what can be done now. First, be patient! The best course of action at this point may actually be to do nothing. Many herbaceous (nonwoody) plants—tender perennials as well as plants that are often evergreen, such as hardy ferns—can be killed to the ground. Leaving the dead top tissue now can provide a bit of insulation for the plants that have survived in the coming weeks. So don’t do extensive cleaning or pruning.

You also don’t want to go with pruning woody plants. Wait until your plants have (or haven’t) flowered in the spring. This will give you the best indication of what to harvest. be patient; Plants such as large-leaved hydrangea (Hydrangea macrophylla and cvs., zones 5-9) may not resume growth until late Mother’s Day, and flower buds (except those developing on new growth) are likely to be damaged by cold temperatures. Also, harvesting now may expose surviving tissue to further chilling damage in the coming weeks.

A close-up of a scratch test on a woody plant

Tip: How to tell if a plant is still alive after an unexpected freeze.

If you are concerned about whether a plant is still alive, you can always do a “scratch test.” This can be done by gently removing (exfoliating) a small area of ​​bark on small stems or twigs to expose the cambium. Green tissue indicates a living stem. If the tissue is brown, it is dead. Keep in mind that different plant tissues (leaves, buds, stems) on the same plant may vary in cold hardiness. Effects may therefore vary due to plant tissue type, age, and health, as well as drainage, snow cover, wind flow, and microclimates.

Plants in containers on decks and patios will suffer more damage than the same plants in the ground. This is because the roots are less insulated from the cold. And one practice that won’t help after this intense stress is fertilization. Whether dead or dormant, plants aren’t taking in many nutrients right now, so don’t fertilize them.

In the short term, be sure to manage any drainage issues to prevent waterlogging on lawns and landscapes that are already stressed. Likewise, monitor moisture levels to ensure that landscape plants, especially evergreens, do not dry out. For long-lived plants, the effects of such stress events may be variable and may take some time to manifest. It is important to understand this and minimize other stresses in the coming months (manage pests, irrigate when needed, prune carefully). As the effects become apparent, we will either be relieved to see the return of old plant favorites or we will have to choose some interesting new plants for our lawns and landscapes.

For more information on winter plant damage prevention and repair, go here.

This article was provided courtesy of the University of Tennessee.

Photos: Courtesy of University of Tennessee



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