After a Freeze: Is it Dead or is it Dormant?

Tropical Giant Spider Lily - pile of mush

Turk's Cap - crispy sticks

Hard freezes in North Texas can render our once lush, colorful gardens to either brown, crispy sticks or piles of mush.   

For those new to gardening you might be thinking your treasured plants are dead.  But are they?    Let me run through a list of common plants in our area and help you discover...is it dead or is it dormant?    And if it's the latter, see instructions below on how to handle your plants to help them return to their pre-freeze glory next spring.

DEAD:

Plants that are only hardy to Zone 10 and above are considered annual plants/flowers in our Zone 7b/8a area. Annual summer flowers, such as Pentas, Periwinkles, Zinnias, Coleus, Caladiums, and Sweet Potato Vine will not survive freezes.  They can be removed now and replaced with cool season annuals like pansies and kale.

If you have a Zone 8b/9 plant, it is considered marginally hardy, and may or may not have been killed by the freeze.   For instance, some websites classify Esperanza Tecoma stans (Yellow Bells) as a Zone 9 plant.  Planted in the ground in a protected spot with a covering of mulch, it may well survive the freeze.    If planted in a container, plants lose one zone of protection from freezes, so it may not survive a freeze.   Mexican Milkweed Asclepias curassavica is another one of those marginally hardy plants.   It may come back from the root, or it may not.   It will usually reseed in our area, though, if it does not come back from the root. 

Look at your plant tag (or Google) to determine a particular plant's hardiness zone, and if it's a marginally hardy plant that has been damaged by the freeze, in late winter (late February), try cutting it back and then waiting for spring to see if it is going to return from the root. 


DORMANT:

Next we'll look at hardy perennials that were sent into dormancy with the freeze.    Their tops might look dead, but their roots are still very much alive and they will flourish again next season.   Here's a list of our most commonly used perennials and how to deal with their post-freeze state:

Any perennials that have turned to mush can be cut right after a freeze:

Daylily
Purple Heart

Garlic Chives
Canna 
Elephant Ear
Tropical Giant Spider Lily

Bear's Breeches
Ligularia/Farfugium (Leopard Plant)


The following perennials can be pruned to the ground after a freeze, but if they have any wildlife benefit (for instance, seed heads), consider waiting until late winter/early spring to cut:

Purple Coneflower
Black-Eyed Susan
Shasta and Ox-eye Daisy
Summer Phlox
Salvia leucantha (Mexican Bush Sage)
Mexican Mint Marigold
Chrysanthemum
Salvia farinacea (mealycup sage)
Salvia guaranitica (Black & Blue Salvia)
Russian Sage
Lantana
Zexmenia
Loosestrife
Flame Acanthus
Catmint
Bee Balm
Hardy Hibiscus
Turk's Cap
Datura
Dwarf Mexican Petunia (Katie's Ruellia) - after a freeze, on a dry day, just stomp on them and break the stems off at the ground and remove browned foliage.


Some perennials also add winter texture and interest, so save pruning for later:       

Salvia Greggii – Give it a slight haircut now to tidy up if desired, but save heavy pruning for February.   In mid-February cut it down to about 6 inches tall and wide.

Aster oblongifolius (Fall Aster) – You can cut it to the ground now; or leave for now for winter texture and interest - then cut to ground in February.

Ornamental grasses - After a hard freeze, the grasses will turn tan, but wait to prune in February.

Butterfly Bush, American Beautyberry:   Leave for now, but cut down to about 18 inches in February

Roses - Prune in February.  Be sure to REMOVE completely if infected with Rose Rosette Disease.


Some perennials are evergreen and may need no pruning after freezes:

Blackfoot Daisy, Calylophus, Pink Skullcap, Dianthus, 4-nerve Daisy, Creeping Phlox - Evergreen.   If no damage, no need to prune.   If any freeze damage, cut any damaged foliage in February.

Lamb's Ear:    Cut or pull away any browned leaves.

Columbine - They will be evergreen through the winter and will bloom in the spring.

Powis Castle Artemisia - Evergreen, but benefits from late winter pruning for fresh new growth.    Wait until February to cut back to about 6 inches tall

Liriope - Evergreen, but again benefits from late winter pruning for fresh new growth.    Wait until February to cut them to the ground (must be cut before March when spring growth starts).

Carex:   Some years they need no pruning at all, but any damaged foliage can be trimmed in late winter/early spring before new growth.  

Hardy Evergreen Herbs (Thyme, Oregano, Winter Savory, Salad Burnet) -  Any damaged foliage can be cut now or wait until February and they should produce new growth.

Cast Iron Plant:   Leave for now, but cut any damaged leaves to the ground late spring (new growth will come in April/May)

Hellebores:   These are winter bloomers.  Cut any damaged leaves to the ground before blooms start, but be careful to not cut any bloom stems that are starting to grow.


Some ferns are evergreen and some are deciduous:

Ferns - Holly Ferns and Autumn Ferns are evergreen, but some years sustain more damage than others.  Prune any browned foliage to the ground in February; sometimes that means cutting the whole fern to the ground; it will come back.  Wood Ferns and Japanese Painted Ferns will go dormant and turn brown after a freeze. Cut them to the ground and mulch.

Wood Fern - dormant after freeze

Dormant, but not pruned:

Macrophylla or Oakleaf Hydrangeas - Do NOT prune. Frozen leaves will fall off leaving only sticks.   Again, do not prune.  If necessary, the only time to prune is immediately after they finish blooming. Pruning now or in the spring will sacrifice next year's bloom.

Hydrangeas after freeze - Do NOT prune

Evergreen, but not frozen:

Some shrubs, like Aucubas, will simply wilt with freezing temps, but as soon as the temperatures are above freezing, they will rebound as if nothing happened.    So no need for action; just patience.

Gold Dust Aucuba wilted in freezing temps

Semi-Evergreen shrubs:

Some shrubs, like Abelias or Sunshine Ligustrum, may have freeze damage to their leaves, but their stems are still fine.  Wait until spring growth comes in the spring to determine extent of freeze damage and cut back to new growth, if needed.

'Rose Creek' Abelia - freeze damaged leaves only

Bottom line, if you have any question about whether a plant will return in the spring, just be patient and wait before you start cutting.

I hope this helps to relieve some concern about your plants after the freeze.     

Happy winter...stay warm and rest up to get ready for spring gardening!    Stay tuned for the Late Winter Pruning newsletter for more details on getting perennials and shrubs ready for spring.

Toni :-)