Fire and Ice in a Southern California Garden

The year 2007 was an odd one for Southern California: a severe freeze in January, extreme heat in late August and early September, and fierce fires in October. Just a few months into 2008, we had an enormous, unexpected bloom to further remind us of Mother Nature’s awesome power. It was a magnificent spectacle of recovery that gave me pause to reflect on the recent events . . .

On the first Sunday of March 2008, I hiked up a steep dirt road off Del Dios Highway between Encinitas and Escondido in San Diego County. It was a road I had passed many times but never had reason to explore before. Now, however, I had reason. Good reason. Stupendous reason. The hillsides above the highway were ablaze in a tapestry of bright orange California poppies (Eschscholzia californica) and deep purple Phacelia. It was an unprecedented display in a part of the county where even old timers couldn’t remember ever seeing a bloom.

What made this year different from all other years were the late October fires of 2007, when the entire chaparral-covered hillside burned, leaving barren slopes and awakening an unremembered seed bank of wildflowers. I’ve driven Interstate 5 through the Grapevine at peak poppy bloom, and I’ve been to the Antelope Valley Poppy Reserve; neither compared to this bloom.

As I stood at the top of the trail and looked down into the river valley, I could see the tall, art deco concrete wall that holds back the waters of Lake Hodges. Downstream from the dam, eucalyptus, oaks (Quercus), and sycamores (Platanus racemosa) bore bright green leaves; this new foliage nearly obliterated bark charred by intense flames that roared through the riverbed just a few months earlier.

First, An Uncommon Freeze

My two-thirds-acre garden is filled with tough plants originating in the mediterranean-climate regions of Australia, South Africa, the Mediterranean Basin, coastal Chile, and, of course, California. The few tender subtropicals live close to the house in a moist “oasis” zone. I’ve learned to grow many of them in pots to protect them from periodic freezes.

People are often surprised to hear that my coastal garden freezes, in Sunset zone 24. Temperatures drop to 25-26°F for four to ten nights each winter, beginning near the end of November. Despite a three-mile, straight-shot to the beach, our property sits in the lowlands of the Olivenhain Valley, which drains into San Elijo Lagoon, one of eight lagoons that separate the coastal cities of northern San Diego County.

Each winter, the cold air rolls down the valley and settles into gardens on my end of the street. The front of my garden lies at seventy-nine feet above sea level, the rear at fifty-five feet. In between are at least nine microclimates, each home to a different complement of plants.

The winter of 2006-2007 started out the same as any other. Just before Thanksgiving, we moved the more tender potted plants onto the patio. Tender plants in the ground were covered with a floating row cover. November went by without a hitch, as did December. January, however, brought the surprise.

Early on the morning of January 15, my neighbor Heather Callaghan called. Her east-facing back patio reached 19°F just before sunrise. I had relied on the thermometer of my new “smart” irrigation clock—the one I chose, in part, because it keeps a record of daily highs and lows. As it turns out, it isn’t so smart when it comes to cold temperatures. The thermometer bottoms out at 32°F. (Why? The manufacturer said that once it gets down to freezing, the temperature is no longer important. Ahem . . . )

So, we estimated. Heather’s patio sits about twenty feet above my front garden, fifty-five feet above my lower garden. It doesn’t sound like much, but it could mean the difference between 19° and 17° or even 15°F. I walked the garden to take an inventory of damage from the freeze. The variegated and dark-leaved aeoniums (Aeonium) had completely melted. Everything else seemed to be just fine—or so I thought.

The next several nights were a few degrees warmer and the garden appeared to be coping. After two weeks, however, damage was everywhere. Why it took so long to become visible was the question. Did it take that long for plant cell walls to break down and their contents leak out? Did the prolonged cold cause more damage than if the cold temperatures had lasted only a few hours? Either way, it would take several months until we knew what survived and what would never come back.

Across the County

Much of Encinitas froze, even within a few blocks of the coastal bluffs, but my neighborhood was worst hit. Other low-lying areas in northern and eastern San Diego County, including parts of Vista, Rancho Santa Fe, Valley Center, Fallbrook, and El Cajon also suffered. Avocado orchards were devastated. Citrus groves were only slightly better off. Palm fronds burned, hedges of eugenia (Syzygium paniculatum) and Indian laurel fig (Ficus microcarpa) were trashed. Lots of paperbarks (Melaleuca) perished. Even old established eucalyptus (including those downstream from Lake Hodges) turned completely brown.

Within days of the freeze, chainsaws were humming almost around the clock. No matter what experienced gardeners and experts advised, few were patient enough to leave in place the damaged branches that might protect still-living plant cores until after the last frost in February or March.

Some of my gardening buddies were overwhelmed and depressed by the damage, but I found it fascinating. I’ve spent years writing and speaking about plants, including their cold hardiness. I usually rely on the experience of others. Here was my chance to see which plants are truly hardy to 25° or 20° or 15°F. It was a real-life test.

I consulted with colleagues in the freeze areas, starting with Andy Maycen and Tom Piergrossi of Tom Piergrossi Landscape Nursery. Their Vista property is hotter in summer than mine, but winters are about the same. Andy reported a low of 18°F three nights in a row, then in the low 20s for five more nights in the coldest pockets.

Andy listed their losses: Metrosideros collina, a strawberry snowball (Dombeya cacuminum), and a rainbow eucalyptus (Eucalyptus deglupta), a Philippine native with gorgeous pastel-mottled bark. Green and gold-striped Bambusa vulgaris ‘Vittata’ and giant Burmese timber bamboo (Dendrocalamus asper) froze to the ground, but resprouted. Giant bamboo (D. gigantea) defoliated, but the old culms leafed out again.

Duranta, Coprosma, several salvias, and hibiscus (Hibiscus chinensis) also froze but recovered. Most varieties of Ficus recovered, but not the lovely, variegated clown fig (Ficus aspera). I lost mine as well—surprising, since its pot was in the warmest and most sheltered area under the eaves on the patio.

Horticulturist Don Schultz at the Water Conservation Garden in El Cajon was the most southerly gardener to report damage. The Garden lost an Aloe cameronii, one of their dragon trees (Dracaena draco), and several cacti. Natal plums (Carissa macrocarpa) planted in open areas froze to the ground, while those near buildings suffered little damage. Jacaranda frosted so badly that it skipped its annual bloom in 2007. One of their trumpet vines (Distictis buccinatoria) froze to the ground, and the garden’s beautiful orchid tree (Bauhinia purpurea) was so badly damaged that it will never be the same.

Don listed other plants that sustained significant damage: oleander (Nerium), yellow oleander (Thevetia peruviana), bird of paradise and giant bird of paradise (Strelitzia regina and S. nicholii), lavender star flower (Grewia occidentalis), cape honeysuckle (Tecomaria capensis), and a tall flame tree (Brachychiton acerifolius). On the flip side, the cold stimulated a fabulous bloom on ‘Howard McMinn’ manzanita (Arctostaphylos ‘Howard McMinn’), grape vines, flowering purple plums (Prunus ×blireiana), evergreen pears (Pyrus kawakamii), fruiting nectarines (Prunus persica var. nectarina), and Western redbud (Cercis occidentalis).

A Neighborhood Survey

Back in Heather’s garden, the branches on a trio of gorgeous fragrant Himalayan champaca (Michelia champaca) froze back to their trunks. It wasn’t the first time they had frozen, but it was certainly the worst. Seeing the damage to the Michelia, Scott Spencer, designer of her garden and my front garden, finally admitted that we indeed garden in a cold sink. He replaced the Michelia with a trio of variegated Brisbane box (Lophostemon confertus ‘Variegata’).

Heather also lost five pink melaleuca (Melaleuca nesophila). A giant tree aloe (Aloe barberae) suffered badly as did Bauhinia. An almost-black-leafed Agonis flexuosa ‘After Dark’ froze to the ground. It eventually resprouted with several trunks and has become an attractive, multi-trunked specimen. Next door, a dozen teenaged, green-leafed A. flexuosa turned brown right away; after about six months, one or two were struggling to recover, but the rest were a total loss.

Elsewhere in the county, chaparral-covered hillsides were dotted with the copper brown leaves of frozen laurel sumac (Malosma laurina). Local avocado farmers often select hillside growing grounds based on the presence of laurel sumac, since the two are said to have a similar cold tolerance. They must be right; avocado groves appeared to be in about the same condition as the sumac.

Other native plants withstood the cold with little problem. In my own garden, not even the least bit of damage appeared on California lilac (Ceanothus), toyon (Heteromeles arbutifolia), fremontia (Fremontodendron), California fuchsia (Epilobium), various oaks, sycamore, hummingbird sage (Salvia spathacea), monkey flower (Mimulus), fescue (Festuca), bush poppy (Dendromecon), Pacific Coast Hybrid irises, and several other natives.

Tender, non-native subtropicals in the ground had varied responses to the freeze. Sky flowers (Duranta spp.) were devastated, though one did come back. I lost two subtropical angel’s trumpets (Brugmansia), but a potted one on the patio resprouted from the base. Red trumpet flower (Brugmansia sanguinea ‘Inca Queen’), which hails from the cool, high elevation Andes, froze almost to the base for the first time ever; after a year, it had regained about half of its height.

A trio of nine-foot-tall, purple crown-shaft king palms (Archontophoenix purpurea) turned brown right away. I left them just in case the inner shafts clung to life, but no such luck. By summer they were as hollow as ping-pong balls.

In June, I finally gave up on the winter cassia (Senna bicapsularis ‘Buttercreme’). I adore the soft yellow popcorn flowers that decorate the garden in fall. A seedling sprouted only a few feet from the dead mother plant, perhaps protected by the dead canopy. The seedling grew astonishingly fast, reaching nearly five feet tall by July. We dug it up and carefully replanted it in its mother’s spot.

Most salvias froze back. Salvia mexicana and anise sage (Salvia guaranitica) typically suffer some burn damage each winter, but this time they froze back to their bases. Even the woodier salvias—blue flowering Salvia ecuadorensis, coppery orange-flowered dune sage (Salvia africana-lutea), and gray-leafed rocky mountain sage (Salvia lanceolata)—suffered badly but recovered.

Two of three canary bird bushes (Crotalaria agatiflora) were damaged. A six-footer near the bottom of the garden froze to the base; I was surprised to find a new sprout on it in the fall. Nature is nothing if not persistent. Nearer the house, a five-footer shrank to three feet but fully recovered. The third and tallest crotalaria suffered only tip burns, thanks to its protected location between the bedroom wall and the neighbor’s eugenia hedge.

I was fascinated by the textbook response of the citrus in our mini-orchard. ‘Oro Blanco’ grapefruit was hardly touched. A few outer leaves on the two mandarins burned. The kumquat was heavy with nearly ripe fruit, many of which became kumquat popsicles.

The inner fruits, though, were the sweetest and longest lasting we’ve ever had; we were still picking kumquats in October! The Eureka lemon had some branch dieback, as did hundreds of lemons in neighborhood groves, but they all recovered within about six months.

Mexican limes were another story. The potted lime on the patio died back to the graft. Leaves, stems, and fruit on the one in the mini-orchard turned the color of straw, and I was sure it was lost, but, with the warm weather of March, it was covered with tiny green leaves. By August, it was in dire need of a haircut. Tree-shaper Ted Overland showed up with his tools and magically erased any hint of the winter carnage.

My garden is framed on two sides with neighbors’ hedges of eugenia. Ugly, messy, hard to keep under control, always infested by one pest or another, they reseed all over the place. When the cold turned their leaves a dried coppery brown, I prayed they would die. No such luck. One neighbor cut his back to single, popsicle-shaped trunks, completely devoid of branches. From our patio, we could see directly into their yard and vice versa. The sudden exposure, punctuated by a line of brown, stubby Eugenia trunks was a shock. Despite talk of replanting with a hedge of Podocarpus, the eugenia remained. The popsicles grew through a shaggy dog stage and, by the following spring, had nearly filled in. At least, we had some privacy again.

A Year Later

It has been more than a year since the freeze happened. We’ve “weathered” some extreme heat and, of course, the wildfires of October 2007. While the fires destroyed acres of property and hundreds of homes and gardens, few spoke of damage to gardens from smoke or ash.

Some plants have been promoted as fire resistant; in truth, few can survive a fire storm of the magnitude of October’s fires. In my travels around the burn areas, it appeared that what was planted in gardens made little difference. I visited areas where ice plant, the prototypical “fire resistant” ground cover, was burned to ashes. The scale-like succulent leaves of native chalk fingers (Dudleya sp.) on the slopes above Lake Hodges burned as crispy as potato chips.

There has been relatively little research into the fire resistance of individual types of plants. In conditions where the wind blows embers around at sixty to eighty miles per hour, construction details and building materials appear to play a far greater role in resisting fire than do garden plants. The most telling report was of a home two miles from the fire’s front line. It was the only home in the neighborhood that burned; an ember landed on its wood shake roof and ignited. All the other homes in the area had composite roofs. Based on my observations, I’d retrofit my home long before I’d make major changes to my garden.

Fire destroys and fire creates. Or at least it opens up new opportunities, like the abundant poppy bloom where no one could remember one before. Freeze, heat, burn. All are part of the cycle. And what a fascinating cycle it is.