Unexpected Hard Frost Predicted

Wow, the forecasted temperatures for tomorrow (Monday) and Tuesday night keep dropping. But if the several inches of snow predicted for Monday materializes, this will be a good thing as snow is an excellent insulator that protects plants during hard-frost events.


Here are a few tips to help protect plants if they need it...


Protecting Recently Transplanted Waterwise Gardening Perennials


For our Waterwise customers, we have been selling a mix of frost-hardened perennials and perennials that have come directly from the greenhouse. Light frosts (28-32°F) will not kill perennials (frost hardened or not) and is not a problem. But temperatures in the low 20’s or teens can be damaging.


If you have not planted your WWG perennials, bring them into the garage or non-freezing space Monday, Tuesday and Wednesday nights. Plant them later in the week or weekend.


If you have planted your perennials;

-many of them have been frost hardened previously (overwintered in our cold frames or cold greenhouse) and will not need protection. It’s easy to identify cold hardened plants as they will just be emerging from the soil in their pots, have purplish colored leaves or are just started to push new leaves from their woody stems.

- Some have not been frost hardened (brought directly from the greenhouse) and can be protected using these methods;

  • Make sure they are well watered.

  • Give some temporary protection like being covered with an upside-down plastic nursery pot (with a rock on top) or plastic garbage bag (anchored around the edges with some rocks to keep from blowing off). 

  • Alternately, if you have a large pine tree under which you can gather brown pine needles, mound the pine needles to completely cover the plants.  Remove once the danger of frost is past. You can use clean wheat or barley straw in the same way.

If you’re not sure if your individual varieties are cold hardened or not see this attached list.


What About Fruit Trees, Flowering Trees and Other Established Plants?


- This is an unexpectedly hard frost (20°F) that will kill fruit tree flowers; too cold to protect them. Other blooming trees will also lose some if not all of their flowers.

- Established perennials, shrubs and trees will be fine, but might experience a little frost-nip on the tips of the new growth.


-Be sure to disconnect hoses from the faucet to avoid pipe damage.


Temperatures will return to seasonal averages from Wednesday on and new transplants won’t need extra cold protection. Cold weather is an ideal time to plant perennials as they enjoy cool temperatures to establish roots before growing their foliage and flowers.




hardened    Plant Name

yes    Achillea fillipendulina Gold Plate (Gold Plate Giant Yarrow)

yes    Achillea millifolium 'Red Velvet' (Red Velvet Yarrow)

yes    Achillea millifolium 'Sonoma Coast' (Sonoma Coast Yarrow)

yes    Achillea Moonshine (Moonshine Yarrow)

yes    Achnatherum calamagrostis (Silver Spike Grass)

no     Agastache cana 'Rosita' (Rosita TX Hummingbird Mint)

no     Agastache cana (Texas Hummingbird Mint)

no     Agastache cana (Texas Hummingbird Mint)

no     Agastache neomexicana (New Mexico Hyssop)

no     Agastache rupestris Grant County, NM (Licorice Mint Hyssop)

no     Agastache rupestris Grant County, NM (Licorice Mint Hyssop)

no     Agastache urticifolia 'AZ Snow' (FlowerKisser™ Arizona Snow Hummingbird Mint)

no     Agastache x 'Ava' (Ava Hummingbird Mint)

no     Agastache x 'Blue Boa' (Blue Boa Hummingbird Mint)

no     Agastache x 'Blue Fortune' (Blue Fortune Hyssop)

no     Agastache x 'Fall Fiesta' (Fall Fiesta Hummingbird Mint)

no     Agastache x Desert Sunrise® (Desert Sunrise Hummingbird Mint)

no     Agastache x Kudos® Mandarin (Kudo Mandarin Hummingbird Mint)

yes   Ajuga reptans 'Catlin's Giant' (Catlin's Giant Ajuga)

yes   Ajuga reptans 'Mahogany' (Burgundy Leaf Ajuga)

no     Ajuga reptans Blueberry Muffin (Blueberry Muffin Ajuga)

yes   Allium x 'Pink Planet' (Hybrid Ornamental Onion)

no     Aloinopsis x Psychedelic (Psychedelic Cold Hardy Mesemb)

yes    Amsonia jonesii (Jone's Bluestar)

no     Anthemis tinctoria 'Susanna Mitchell' (Susanna Mitchell Marguerite Daisy)

yes    Aquilegia 'Little Treasure' (Little Treasure Golden Columbine)

yes    Aquilegia aff longissima Swallowtail® (Swallowtail Columbine)

yes    Aquilegia caerulea (Rocky Mountain Columbine)

yes    Aquilegia chrysantha (Goldern Columbine)

yes    Aquilegia desertorum (Arizona Columbine)

yes    Aquilegia desertorum (Arizona Columbine)

yes    Aronia melanocarpa 'Iroquois Beauty' (Iroquois Beauty Chokeberry)

yes    Aronia melanocarpa 'Iroquois Beauty' (Iroquois Beauty Chokeberry)

yes    Artemisia x 'Powis Castle' (Powis Castle Sage)

yes    Aster x frikartii Monch (Monch Hybrid Aster)

no     Berlandiera lyrata 'Mora County' (Chocolate Flower)

no     Bouteloua gracilis 'Blonde Ambition' (Blonde Ambition Blue Grama Grass) PP#22,048

yes    Buddleia alternifolia 'Argentea' (Silver Leaf Spring Blooming Butterfly Bush)

no     Bulbine abyssinica (Golden Stars)

yes    Calamintha nepetoides 'White Cloud' (White Cloud Calamint)

yes    Campanula rotundifolia (Bluebells)

yes    Centranthus ruber 'Coccineus' (Red Jupiter's Beard)

yes    Cerastium tomentosum (Snow-in-Summer)

yes    Ceratostigma plumbaginoides (Hardy Plumbago)

no     Cold-hardy Cactus Assortment

yes    Coreopsis verticilata 'Zagreb' (Zagreb Threadleaf Tickseed)

no     Cotyledon orbiculatus (Red Edged Pig's Ear)

yes    Dalea purpurea (Purple Prairie Clover)

yes    Dasylirion wheeleri (Sotol)

no    Delosperma ashtonii 'Blut' (Blut Cold Hardy Ice Plant)

no    Delosperma cooperi (Purple Ice Plant)

no    Delosperma nubigenum (Yellow Ice Plant)

no    Delosperma Red Mountain® Flame (Red Mountain Flame Ice Plant)

no    Delosperma sphalmanthoides (Miniature Ice Plant)

no    Delosperma x Delmara® Yellow (Yellow Hybrid Ice Plant)

no    Delosperma x Granita® Orange (Granita Orange Ice Plant)

no    Delosperma x Granita® Raspberry (Granita Raspberry Ice Plant)

no    Delosperma x Jewel of Desert® Garnet (Desert Garnet Dwarf Ice Plant)

no    Delosperma x luckhoffii 'Orange Burst' (Orange Burst Dwarf Ice Plant)

no    Delosperma x luckhoffii 'Scarlet Burst' (Scarlet Burst Dwarf Ice Plant)

yes   Dianthus gratianopolitanus 'Firewitch' (Firewitch Cottage Pink)

yes   Echinacea purpurea 'Mellow Yellows' (Mellow Yellows Purple Coneflower)

no    Echinacea purpurea 'Ruby Star' (Ruby Star Purple coneflower)

no    Echinacea purpurea Pow Wow® Wild Berry (Pow Wow Wild berry Purple Coneflower)

no    Echinacea x 'Cheyenne Spirit' (Cheyenne Spirit hybrid Coneflower)

no    Echinacea x Sombrero Slasa Red (Sombrero Salsa Red hybrid Coneflower)

no    Echinops bannaticus 'Blue Globe' (Blue Glow Globe Thistle)

no    Engelmannia peristinia (Engelmann Daisy)

no    Eriogonum umbellatum 'Gentle Giant' (Gentle Giant Sulfur Buckwheat)

yes   Eriogonum umbellatum 'Poncha Pass' (Poncha Pass Sulfur Buckwheat)

yes   Eriogonum umbellatum 'Poncha Pass' (Poncha Pass Sulfur Buckwheat)

yes   Eryngium yuccafolium (Rattlesnake Master)

no    Eschscholzia californica 'Mikado' (Mikado California Poppy)

yes   Festuca glauca 'Boulder Blue' (Boulder Blue Festuca Grass)

no    Festuca x 'Siskiyou Blue' (Siskiyou Blue Festuca Grass)

yes   Forestiera neomexicana 'Happy Boy' (Happy Boy New Mexico Privet)

yes   Forestiera neomexicana Berry Girl (Berry Girl New Mexico Privet)

no    Gaillardia grandiflora 'Arizona Sun'

no    Gaillardia grandiflora Arizona Apricot (Arizona Apricot Blanket Flower)

no   Gaillardia grandiflora Arizona Red Shades (Arizona Red Shades Blanket Flower)

yes  Gallium odoratum (Sweet Woodruff)

yes   Gaura lindheimeri 'Rosy Jane' (Pink Appleblossom Grass)

no    Gaura lindheimeri Intermountain Beauty (Appleblossom Grass)

no    Gazania x Butterscotch Baby (Butterscotch Baby African Daisy)

yes    Geranium x 'Rozanne' (Rozanne Perennial Geranium) PP#12,175

no    Helianthemum nummular 'Belgravia Rose' (Pink Rock Rose)

yes   Helianthus maximiliana 'Santa Fe' (Santa Fe Maximilian's Perennial Sunflower)

yes   Helichrysum tianshanicum

yes   Hesperaloe parviflora Coral Glow (Coral Glow TX Red Yucca) PP29,626

yes   Hesperaloe parviflora Coral Glow (Coral Glow TX Red Yucca) PP29,626

yes   Hesperaloe parviflora open pollinated (Texas Red Yucca)

yes   Hesperaloe parviflora Straight Up Red (Straight Up Red TX Yucca)

yes   Hesperaloe parviflora Straight Up Red (Straight Up Red TX Yucca)

no    Heuchera bryzoides 'Weston Pink' (Weston Pink Coralbell)

yes   Hymenoxys scaposa (Thrift Leaf Perky Sue)

yes   Kniphofia x 'Fireglow' (Fireglow Red Hot Poker)

yes   Lamium maculatum 'Red Nancy' (Red Nancy Deadnettle)

yes   Lamium maculatum 'White Nancy' (White Nancy Deadnettle)

yes   Lavandula angustifolia 'Buena Vista' (Twice Blooming English Lavender)

yes   Lavandula angustifolia 'Wee One' (Wee One Dwarf English Lavender)

no    Lavandula angustifolia 'WWG02' (FlowerKisser® After Midnight English Lavender)

no    Lavandula angustifolia 'WWG02' (FlowerKisser® After Midnight English Lavender) 5"

yes   Lavandula x intermedia Gros Bleu (Big Blue French Hybrid Lavender)

yes   Liatris ligulistylus (meadow blazingstar)

yes   Liatris mucronata (Texas Blazing Star)

yes   Long Blooming Waterwise Garden I

yes   Lonicera reticulata 'Kintzley's Ghost' (Lonicera reticulata 'Kintzley's Ghost')

yes   Lonicera sempervirens 'John Clayton' (Yellow Honeysuckly Vine)

yes   Lonicera sempervirens 'Major Wheeler' (Major Wheeler Honeysuckle Vine)

yes   Lonicera sempervirens Orange (Orange Honeysuckle Vine)

no    Mirablis multiflora (Wild Four O'clock)

yes   Monarda bradburiana (Eastern Beebalm)

yes   Monardella villosa 'Russian River' (Russian River Coyote Mint)

yes   Nepeta x 'Junior Walker' (Junior Walker Catmint) #23,074

no    Nepeta x Little Trudy® (Little Trudy Dwarf Catmint) PP18,904

yes   Oenothera fremontii 'Shimmer' (Shimmer Evening Primrose )

no    Oenothera macrocarpa 'Comanche Campfire' (Shimmer Evening Primrose )

yes   Oreganum x 'Bristol Cross' (Bristol Cross Ornamental Oregano)

yes   Oreganum x 'Erntedank' (Thanksgiving Ornamental Oregano)

yes   Origanum libanoticum (Cascading Ornamental Oregano)

no    Papaver somniferum 'Lauren's Grape' (Lauren's Grape Beardseed Poppy)

yes  Papaver x intermedia (Double Orange Oriental Poppy)

no    Paronychia kapela ssp. Serpyllifolia (Nailwort)

no    Pelargonium x Black Boar (Black Boar Geranium)

yes   Penstemon barbatus Elfin Pink (Elfin Pink Beardtongue)

no    Penstemon digitalis 'Dark Towers' (Dark Towers Beardtongue)

yes   Penstemon pinifolius 'Compactum' (Compact Pineleaf Beardtongue)

yes   Penstemon pinifolius 'Compactum' (Compact Pineleaf Beardtongue)

no    Penstemon pinifolius 'Luminous' (Luminous Pineleaf Beardtongue)

yes   Penstemon pinifolius 'Magdalena Sunshine' (Magdalena Pineleaf Beardtongue)

no    Penstemon pseudospectabilis 'Coconino County'

no    Penstemon strictus (Rocky Mountain Beardtongue)

yes   Penstemon superbus (Superb Beardtongue)

yes   Penstemon x mexicale Pikes Peak Purple® (Pikes Peak Purple Hybrid Beardtongue)

yes   Penstemon x mexicale Red Rocks® (Red Rocks Hybrid Beardtongue)

yes   Perovskia atriplicifolia 'Blue Spires' (Blue Spires Russian Sage)

no    Petunia eximia (Brazilian Red Petunia)

yes   Philadelphus microphyllus 'Desert Snow' (Desert Snow Littleleaf Mock Orange)

yes   Phlox paniculata 'Jeane' (Jeane Garden Phlox)

yes   Pulsatilla vulgaris 'Rosen Glocke'

yes   Ribes aureum v aureum (Buffalo Currant)

yes   Rosmarinus officinalis  'Madaline Hill' (Madaline Hill Hardy Rosemary)

yes   Rosmarinus officinalis 'Alcalde Cold Hardy' (Alcalde Cold Hardy Rosemary)

yes   Rosmarinus officinalis 'Santa Fe Dark Blue' (Santa Fe Dark Blue Rosemary)

no    Ruschia pulvinaris (Creeping Shrubby Ice Plant)

no    Ruschia punctulata (Hantamberg Ice Plant)

no    Salvia chamaedryoides (Germander Sage)

no    Salvia coccinea 'Jewel Red' (Jewel Red Sage)

no    Salvia darcyi (Vermillion Bluffs Mexican Sage)

yes  Salvia greggii "WWG03' (FlowerKisser® Coral Pink Sage)

no    Salvia microphylla 'Hot Lips' (Hot Lips Littleleaf Sage)

yes   Salvia pachyphylla 'Mulberry Flambe' (Mulberry Flambe Mojave Sage)

yes   Salvia sylvestris 'Caradonna' (European Meadow Sage)

yes   Salvia sylvestris 'May Night' (May Night European Meadow Sage)

no    Salvia x 'Burgundy Seduction' (Burgundy Seduction hybrid Sage)

no    Salvia x 'Indigo Spires' (Indigo Spires Sage)

yes   Salvia x 'WWG01' (FlowerKisser® Dark Shadows Sage)

yes   Saponaria ocymoides (Soapwort)

yes   Scrophularia macrantha (Red Birds in a Tree)

yes   Scutellaria x 'Dark Violet' (Dark Violet Hybrid Skullcap)

yes  Scutellaria x 'Dark Violet' (Dark Violet Hybrid Skullcap)

no    Sedum spurium 'Red Carpet' (Red Carpet Stonecrop)

no    Sempervivum, assorted dwarf cultivars (Dwarf Hens and Chicks)

yes   Sporobolus wrightii 'Windbreaker' (Windbreaker  Giant Sacaton Grass)

yes   Stachys byzantina 'Helen von Stein' (Helen von Stein Lamb's Ear)

no    Stachys lavandulifolius (Cottoncandy Lamb's Ear)

no    Stomatium species 'Sutherland' (Night Blooming Ice Plant)

yes   Tanacetum densum v amani (Partridge Feather)

no    Teucrium aroanum (Creeping Silver Germander)

no    Thymus praecox v. arcticus 'Coccineus' (Pink Creeping Thyme)

no    Thymus pseudolanuginosus (Wooly Creeping Thyme)

no    Thymus Reiter (Reiter Thyme)

yes   Thymus vulgaris 'Fredo' (Fredo Culinary English Thyme)

no    Thymus x 'Pink Chintz' (Pink Chintz Creeping Thyme)

no    Verbena peruviana (Red Devil Creeping Verbena)

no    Verbena peruviana (Red Devil Creeping Verbena)

no    Veronica liwanensis (Turkish Speedwell)

no    Veronica oltensis (Thymeleaf Speedwell)

no    Veronica x 'Royal Candles' (Royal Candles Speedwell)

no    Veronica x Blue Reflection® (Blue Reflection Hybrid Speedwell)

no    Viola cornuta 'Bowles Black' (Black Viola)

no    Viola tricolor 'Helen Mount' (Johnny Jump Up)

no    Viola x 'Yellow Delight' (Yellow Viola)

yes   Yucca rostrata (Big Bend Yucca)

yes   Yucca schottii (Schott's Yucca)

yes   Zauschneria canum v latifolia Sky Island Orange (Sky Island Orange Hummingbird Trumpet)

yes   Zauschneria latifolia 'Woody's Peach Surprise' (Woody's Peach Surprise Hummingbird Trumpet)

yes   Zaushneria arizonica (Arizona Hummingbird Trumpet)

yes   Zinnia grandiflora Golden Eye (Prairie Zinnia)


Waterwise Gardening Plant Guarantee

Our plants are carefully pickedfor you order by our experienced staff. All sales are Final.

Plants are guaranteed to be healthy and strong when leaving our greenhouses. After they leave our care, the plants are your responsibility. Please read and follow our planting instructions for best results. 



© All articles are copyrighted by WATERWISE Gardening, LLC.

Republishing an entire WATERWISE Gardening blog post or article is prohibited without written permission. Please feel free to share a short excerpt with a link back to the article on social media websites, such as Facebook .


Share on Facebook
Share on Twitter
Please reload

Featured Posts

Pruning Conifers

May 20, 2019

Please reload

Recent Posts

September 14, 2020

Please reload

Please reload

Search By Tags