CA freeze post mortem

Medit-Plant list members:
I have prepared the report below mainly for my own records, but I hope
some of you — particularly western U.S. gardeners and Zone 7-9 gardeners
— will find some of this information useful. Since I have a sizable
collection of salvias, gardeners of this species may take special note.
The cold-hardiness of many salvias is not certain, since many species,
hybrids and cultivars have only recently become commercially available.
Your comments and feedback are welcome. — P.H.

TEMPERATURE DATA
Recorded low temperatures: Dec. 20 (28F), Dec. 21 (18F), Dec. 22 (20F),
Dec. 23 (20F), following 7 inches of snow the week before.

GARDEN LOCATION
Generally warm knoll top at 2,700 feet near Nevada City, CA (50 miles NE
of Sacramento), Sierra Nevada foothills. Garden area (a mix of perennial
borders and raised rock garden beds) is in an open area, slightly down
sloping, between deciduous black oaks and Ponderosa pines that reduce
sun exposure in summer to “full sun” plants’ minimum requirements. The
garden is sheltered by the house from prevailing winds from SW. Garden
plants are predominantly a mix of Mediterranean and native
California/Sierra foothill plants.

SUMMARY
The cold weather event caused moderate or severe damage to plants rated
for Sunset Zone 8 and higher in cold-hardiness. The freeze was useful in
clarifying the cold-hardiness dividing line between Zone 7 and higher.
Also, the freeze raised questions about whether several plants rated
above Zone 7 for cold-hardiness are rated accurately by “experts.” Some
late-emerging, late blooming (autumn) perennials, such as salvia
leucantha (Mexican bush sage), salvia X “Indigo Spires” and salvia
elegans (pineapple sage) that are rated Zone 8 or Zone 7 will need more
time to reveal whether they survived.

~~~~~ Zone ratings listed refer to a minimum zone rating for
cold-hardiness. ~~~~~

FATALITIES
• Lavatera maritima “Rosea”/tree mallow — Zone 8. Was exposed to wind
and was planted in a oak barrel, which reduced its cold-hardiness.
• Salvia clevelandii “Whorly Blue” — Zone 10? Young plant, newly
planted. Probably under stress already.
• Lavendula dentata/French lavender — Zone 8. Was growing in a container
and was exposed to wind. Was sensitive to frost at higher temps.
• Salvia elegans/pineapple sage — Zone 8. Two 3-year-old plants were in
containers and exposed to wind. One plant seems to have died. The other
just this week began growing a couple new leaves from the base of the
basal stem.
• Salvia brandegi/Brandegee’s sage/Santa Rosa Island sage — hardy to 20
degrees according to noted salvia expert Betsy Clebsch. Was a recent
transplant.
• Salvia mellifera “Terra Seca”/Black sage— hardy to 30F-32F according
to Cabrillo College Hort. Dept. Was a recent transplant.

MODERATE/SEVERE DAMAGE (but showing signs of recovery)
• Salvia chamaedryoides/Germander sage — Zone 8 (Cabrillo College Hort.
Dept. says hardy to 15F-20F). Lost all foliage. Most branches died. New
foliage showing from basal stems on some plants. Was in shade (for
winter only).
• Mimulus auranitica (and various cultivars of CA coastal natives), and
Sierra native mimulus bifidus. Plants generally died back to the ground,
losing foliage on older woody stems. Most are showing new foliage
growing from basal stems. Some plants were in shade for winter. Others
were in full sun, with similar frost damage.
• Salvia leucophylla x ?“Bee’s Bliss” (s. leucophylla x sonomensis or
clevelandii) — unknown cold-hardiness (probably 20F). Almost entire
plant’s foliage died. A few sprigs of newer growth survived.
• Salvia “Dara’s Choice” (s. sonomensis cultivar). Same as above. Plant
was young and newly transplanted.
• Salvia clevelandii "Winnifred Gillman" — Zone 10. Frost burn to many
leaves.

SLIGHT DAMAGE
• Caryopteris clandonensis/Blue Mist shrub (unknown cultivar with pale
blue flowers and gray-green foliage) — rated all zones. Leaf buds that
are partially open on stems during winter, were severely burned, but new
leaves have replaced them.
• Salvia greggii/Autumn sage — Zone 8 (?). Several cultivars (white,
purple, red flowering varieties) in garden. Some frost burn to leaves.
Probably hardier than Zone 8.
• Salvia x “Vicki Romo” (hybrid between s. apiana and either leucophylla
or clevelandii) — hardy to 20F (Clebsch). Some foliage frost burned.
• Phlomis lanata/Jerusalem sage — Zone 7. Some frost burn to a few
leaves.

UNDAUNTED (a few selected plants worth noting)
• Fremontodendron  — Zone 7.
• Salvia uliginosa/Bog sage — Zone 8. Probably is hardier than Zone 8.
• Salvia apiana — Zone ? Had recently transplanted a large specimen, but
it didn’t flinch from either transplanting or freeze.
• Salvia forskaohlei/Forskahl’s sage — Cabrillo College Hort. Dept. says
rated to 25F-30F, but is probably much hardier. Showed no damage to
large over-wintering leaves.
• Salvia sclarea (including young seedlings) — all zones.
• Salvia pratensis — rated to 15F-20F. No damage.
• Salvia pratensis ssp haematodes — rated to 15F-20F.
• Salvia superba (various cultivars/hyrbids)— all zones.
• Salvia verticillata “Purple Rain” — all zones.
• Salvia moorcroftiana — hardy to 0F (Clebsch)
• Quercus chrysolepis/Canyon Live Oak — Zone 9. Was in a large plastic
container.

UNKNOWN CONDITION
(These salvias usually do not show new growth until late winter or early
spring)
• Salvia leucophylla/Purple sage — Zone 8. Almost all leaves fell off
stems. Few new leaves have returned. Usually sensitive to frost, this
4-year-old shrub had been under stress from a recent transplanting.
• Salvia leucantha/Mexican bush sage — Zone 10. Has not emerged from
winter dormancy.
• Salvia involucrata/Roseleaf sage — Zone 8 (Cabrillo College Hort.
Dept. says hardy to 15F-20F). Showing some new leaves at base. Probably
will survive.
• Salvia guaranitica — Zone 8. Showing some new leaves at base. Probably
will survive.
• Salvia confertiflora — hardy to 10 degrees (Clebsch). No sign of new
growth, but usually late in emerging from winter dormancy.
• Salvia x “Indigo Spires” — rated to 15F-20F. Two of three plants show
some new growth on basal stems.
• Salvia transylvanica — rated by Clebsch to 0F. Some new growth, but
took a hard hit, which suggests it is not as cold hardy as some think.

Other observations worth noting:
• Tough lupines: Seedlings and young plants of the native CA coastal
Lupinus arboreus (grown from seeds collected them beach dunes in the
Eureka CA area) were a worry, but came through the freeze mostly
unscathed. A knowledgeable friend said these lupines wouldn’t be hardy
because they are native to the marine climate. My other native lupines
(l. polyphyllus, l. argenteus) and annual wildflower lupines sowed in
the fall were completely unaffected by the freeze.

Paul Harrar
Nevada City, CA
Sunset Zone 7, 2,700 ft.
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