From The Santa Cruz Sentinel
August 25, 2005

Work with the climate to keep plants thriving

Abbie Blair: Native plants

Almost all of us have at one time or another come back from vacation with plant material in tow from an exotic location: tropicals from Hawaii or cacti from the desert. No matter how much we pamper and follow attached detailed instructions, many plants just never adjust to the new environment. They either struggle or die. Hands down, climatic conditions are some of the biggest factors contributing to the success or failure of a plant.

Plants can thrive or die due to even subtle climatic changes from seaside to sunny foothills.

For decades, climatic data has been complied and maps generated to help make sense of local growing conditions. In the 1930s, Sunset Magazine began mapping the western states, taking into consideration the unique climatic growing conditions along with the traditional data of minimum and maximum temperatures, latitude, elevation, ocean influence, continental air influence, mountains and hills and the local topography.

Today the map has become known by many as the gold standard for western growing advice. Zones are numbered from the harshest (Zone 1) in the north to the mildest (Zone 33) in the south.

To accompany the map a plant encyclopedia was developed that assigned the appropriate zone(s) for each plant. The system helps take the guesswork out of plant selection.

"The great thing is that you can look up a plant and find out where it will grow," says Lance Reiners, who has been helping people with their gardening questions for more than 15 years at the Garden Company in Santa Cruz.

Finding your zone
Our area contains four zones. To find the one which your garden falls in, read the descriptions to match your geography, then select plants compatible to your zone and reap the benefits of your selections.

If your garden falls in Zone 16, as in the foothills east of Watsonville, take advantage of the banana belt climate to grow "subtropicals like citrus and ginger," says Reiners.

In Zone 17, mostly along the coast, lavish yourself with how abundantly "fuchsias, begonias and stock will grow," adds Reiners.

Zone 15, in the redwoods, still has enough cold days for peonies to bloom and green veggies like cabbage, broccoli and artichokes will thrive.

Tuning the zone
If your zone description seems a touch off, you may be located in a microclimate.

"We like to say at Sunset that the zones send people to the ballpark and microclimates send them to home plate," says Kathleen N. Brenzel, Senior Garden Editor of Sunset Magazine.

Microclimates can be small or relatively large areas. To get on base become a climate sleuth. Gather clues from the local topography to discover if you are gardening in a microclimate.

"Look around, is there a coastal canyon? Look at the conditions around you, are there cold air areas, certain places that get occasional frost?" questions Brenzel.

If the answer is yes, your garden may lie in a microclimate slightly colder than the zone average. Gather information from existing plants, "look around at your neighbor’s yard and in your own," suggests Brenzel. Notice what is thriving and what has failed. Modify your selections with your new information.

Pushing the zone
Continue sleuthing further to find the hidden microclimates in your own yard. Where are the warm and cold areas? Heat-loving plants can be aided by a few extra degrees generated by a brick or rock wall. Cold loving plants like peonies can realize a few more hours of cold when planted in a low open area.

"Take temperatures in the garden," comments Brenzel. You may be surprised at the variation that exists created by plants or buildings. Capitalize on these areas to widen the range of plants in your garden.

Below the zone
Soil quality is not taken into consideration in zone mapping. Since the soil houses the water and nutrient uptake system for most plants, it plays an important role. Most plant guides describe soil requirements in terms of well-drained, acid or alkaline, poorly drained or high organic matter. Many soils can be modified with amendments or by the use of raised beds.

Zone expertise
If you are new to gardening or just stumped, seek out local resources for gardening advice. The Master Gardener Program maintains a phone hotline at 763-8007, local nurseries have years of local gardening expertise to share, and Sunset Magazine publishes the "Western Sunset Garden Book," by Editor Kathleen N. Brenzel and hosts a demonstration garden at the magazine headquarters in Menlo Park.

Santa Cruz County’s zones

ZONE 7 — Thousands of acres fall into this zone, including middle elevation areas in the state. Here, it’s the Felton area and ridge tops along the Santa Cruz Mountains, where native gray pine (Pinus sabiniana) forests are found. Hot summers and mild, well-defined winters create recognizable seasons. In such a large area, lows vary, however typical winter lows range from 9 to 23 degrees (all temperatures in Fahrenheit).

ZONE 15 — This area winds it way throughout the area covering most of the Santa Cruz Mountains, where Zone 7 leaves off, and is marked by flourishing redwoods. It continues north of Santa Cruz east of Highway One past the county line. It is influenced by marine air approximately 85 percent of the time and the remaining 15 percent of the time by inland air. In general this zone has a moist atmosphere, cool summers and mild winters. Afternoon winds are common. Lows over a 20-year period ranged from 21 to 28 degrees.

ZONE 16 — This zone meanders east of Watsonville north along the foothills including the Corralitos area and inland to the Aptos area. This zone is known for its summer afternoon winds. It is dominated by marine air 85 percent of the time and by inland air the rest of the time. The area has a temperate feel from the combination of thermal belts and the coastal influence, with summers warmer than Zone 17 and winters warmer than Zone 15. Lows over a 20-year period ranged from 19 to 32 degrees.

ZONE 17 — This zone hugs the coastline on the west side of Highway One. Mild wet usually frostless winters are accompanied by almost daily blankets of fog. Average winter lows over a 20-year period ranged from 23 to 36 degrees.

Abbie Blair, a member of the California Native Plant Society, has a degree in horticulture and has spent 25 years in plant and cut flower production, at one point operating a nursery in Gilroy. She lives on Mount Madonna and is waging hand to vine combat against the ivy and vinca displacing the native plants. Contact her at svreeken@santacruzwsentinel.com.