While much of California has a Mediterranean climate with hot, dry summers and cool, moist winters, there are many distinct microclimatic variations within our state. A microclimate is defined as a local atmospheric zone where the climate differs from the surrounding area. It can be as small as a few square feet or cover hundreds of square miles.
Paradise, Magalia, Forest Ranch and Berry Creek lie within Zone 7. This area has hot summers and relatively mild, but pronounced winters. Late-blooming deciduous fruit trees (apples, pears, cherries), do well in this zone. Winter lows range from 23° to 9°F and the frost-free growing season normally lasts from the beginning of May to mid-October.
Sandwiched between Zones 7 and 8 is the thermal belt of Zone 9. Cold air flows downhill from Zone 9 to the valley floor. Oroville and other lower foothill areas are found in this zone. Zone 9 has a similar growing season to Zone 8 (mid-February to late November), but the lows here are not quite as extreme, ranging from 28° to 18°F. These slightly higher winter temperatures mean that not only can the plants and crops that do well in Zone 8 thrive, but many cold-sensitive plants too can succeed in Zone 9.
- Low spots collect rainwater and/or cold air resulting in localized frost pockets or boggy areas. Hilltops are more exposed to drying winds. Barriers across slopes, such as walls, fences or rocks can provide shelter from winds, but can also cause cold air to pool behind them. Making gaps in the barrier can allow the air to drain and prevent possible frost pockets. Water flows off sloped areas before completely soaking in, so slopes tend to be drier than flat surfaces.
- South-facing areas get more light and heat than areas facing in other directions; a south-facing wall accentuates this as it absorbs and reflects heat. Conversely, a north-facing slope or the north side of a fence or a wall will be more shady and cool. Temperatures in west- and east-facing areas fall in-between north and south aspects, with western aspects being slightly warmer since they are exposed to the hot afternoon sun.
- Clay soils tend to hold water more than sandy soils, so poor drainage can be associated with clay soil, while sandy soils can drain too fast and dry out too quickly. Loamy soil strikes a balance between these two extremes. Heat is stored in soil water during sunny days and that heat is re-radiated at night. Moist soil can store more heat than dry soil, thus reducing frost risk. Dry sandy soils or recently cultivated soils with many air pockets reduce the storage of heat in soil water during the day and are therefore colder at night, increasing the risk of frost damage.
- Trees and shrubs create shade and can provide windbreaks as well. A dense tree canopy may trap heat at night, moderating nighttime temperatures. Because trees compete for sunlight and for water and nutrients in the soil, it can be difficult for other plants to survive beneath them.
Man-made Structures. A house absorbs heat during the day and re-radiates heat at night. A house affects wind patterns, creating turbulence and causing higher wind speeds to occur along its walls. The lee side may be in a “rain shadow” when rain is driven by strong winds. Rainwater flowing off roofs or out of downspouts can create wet spots if it doesn't drain properly. Balconies high above ground level may avoid frost, but they are often exposed to more wind. Raised beds usually warm up and dry out earlier in the spring. Paved surfaces act as “heat islands,” absorbing and reradiating the sun's energy.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at (530) 538-7201. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us Hotline webpage.
- Author: Sherida Phibbs
Selecting plants is not a “one-plant-fits-all” approach. Trees, shrubs, plants, vegetables, etc., all have their own climate requirement to grow and produce at their best. Knowing your planting zone is the first key element in selecting your landscape plants and trees, knowing when to plant your vegetable crops and knowing if certain fruit trees and berries will be successful in your area.
The USDA Cold hardiness zones are based on winter minimum temperatures. The AHS (American Horticultural Society) heat zone system is based on average number of days above 86 degrees F. Since these two systems are limited, the best and most reliable system is the Sunset Zone.
We recommend using the Sunset zone system. This system bases its climate zones consisting of many factors: cold, heat, humidity, wind, proximity to the Pacific Ocean, snow cover, and the length of the growing system.
The Humboldt and Del Norte Counties consists of 6 Sunset Zones. Zone 17 is the maritime zone for both counties. Zone 1a is the Costal Range Mountains for both counties. Zone 15 is Humboldt's costal zone, 14 is the interior zone and transitional zones are 4 and 7. Del Norte's transitional zone is 7. To determine your zone visit our Website to find your location on the Sunset Map.
Most all landscapes and gardens have microclimates. These are areas in your gardens that are influenced by various factors: i.e. exposure to wind, structure walls, sloping ground, dry banks, eaves and overhead structures and trees.
Shade trees and overhead structures will provide planting areas for shade loving plants. During a frosty evening, this area will be a few degrees warmer than the air over the open ground.
Masonry and stucco south and west walls soak up solar energy during the day and then releases it at night. In our counties cooler summer days, it will help to provide the warmth that heat loving vegetables require during the day and the evening.
North walls get little direct sun. This is a perfect location for woodland plants like ferns.
East walls generally can get up to half a day of sun and is less intense than a west facing wall. Azaleas and fuchsias generally will be happy.
Eaves will provide frost protection for delicate flowers.
Sloping grounds make a perfect location to grow citrus as the air flow is warmer than the air on hilltops or in the valleys below.
Drought tolerant plants would be the best solutions for planting in dry bank areas.
Cold air pockets lay in low-lying areas. This is a benefit for tulips which needs that extra chill to encourage bloom. These cold pockets are also good locations for certain fruit trees and berries which require cold periods for production of fruit.
Get to know your garden and plan your selection of plants and plant site location. Use microclimates to your advantage to be successful with your vegetable gardens and your landscape.
Source: The Western Sunset Zone 2017 Third Edition
By Susanne von Rosenberg, U.C. Master Gardener of Napa County
After you have been gardening a while, you may want to branch out and try growing more unusual plants. Being successful with less common plants requires more knowledge and research. Experience helps, too.
Uncommon plants fall into three categories. Some are simply unfamiliar but not difficult to grow, such as watermelons that don't have red flesh. (I like ‘Cream of Saskatchewan,' which has a creamy white interior.) We're all familiar with pluots (a 75 percent plum-25 percent apricot cross), but there are also plumcots (equal parts plum and apricot) and apriums (25 percent plum-75 percent apricot), as well as a cherry-plum cross. All of these crosses can thrive in Napa Valley, but be sure to check the basics before planting them. Does your microclimate provide enough hot days to ripen that watermelon, or enough chill hours for the aprium?
Other uncommon plants may be more challenging because you don't know anyone who has grown them. The jujube (also known as Chinese date or red date) is a fruit tree that at least one Napa County nursery offers in bare-root form. But do you know anyone who has grown one?
For such plants, you need to research the pros and cons yourself. Jujubes have spines on young wood, require unusual pruning techniques and tend to sucker. On the positive side, they thrive in almost any soil, are drought-resistant, have a long productive life (more than 50 years), often fruit within two years of planting and produce nutritious fruit.
Other plants may be rare in Napa County because they are difficult to grow here. They may not like our climate or need more day length than we have. While you can modify climate somewhat (depending on how much time and money you want to invest), there is little you can do about day length.
Plants from equatorial areas are used to a consistent 12 hours per day of sunlight and may not flower or fruit if the daylight period is longer or shorter. Chayote squash tends not to set fruit in Napa Valley until late August or early September, when the days are shorter, and then our growing season is cut short by frost before the squash have time to mature.
Before planting any uncommon plant, find out whether it is invasive in California. A few years ago, I became enthralled with a plant called autumn olive, also known as silver berry. Then I learned that it is considered invasive everywhere it is found. Even so, you can still buy it in nurseries, including on-line nurseries.
Next, think carefully about your microclimate. Consider how much sun or shade the plant requires, how much heat it needs or can tolerate and whether it requires some winter chill. Is the plant frost- or wind-sensitive? What are its needs with regard to humidity? What is its typical growing season, and is our growing season long enough for it to mature fruit?
What kinds of pests and diseases does this plant suffer from in its native habitat, and do we have any of these pests and diseases in Napa Valley? Make sure the plant can thrive in your type of soil and that, when full grown, it will fit in your garden. I was thinking about planting pecan trees until I learned that they typically grow 65 to 130 feet tall.
Finally, think carefully about how much time and money you want to invest. You could grow bananas in a heated greenhouse in our climate. Do you want to spend the money to install and heat a greenhouse?
Do your research using reliable sources such as the University of California Cooperative Extension, other university websites, information from U. C. Master Gardeners, reputable nurseries and other recognized authorities such as the California Rare Fruit Growers or California Native Plant Society. When considering information from other universities, be aware that their recommendations are based on the climate in that region.
Enjoy your explorations and let U. C. Master Gardeners of Napa County know what types of unusual plants you have growing in your yard.
The UC Master Gardeners of Napa County are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.
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By T. Eric Nightingale, U.C. Master Gardener of Napa County
Gardening and a love for nature is on the rise these days. Many people I know would like to garden more but believe they can't because they live in an apartment or have only a small yard. That's not so. While they may not be able to have massive oaks or cultivate long rows of tomatoes, there are still many ways to grow plants.
The first task in any small space, be it a balcony or yard, is to understand the microclimate. Small yards are often protected from the elements by overhanging roofs and fences, while balconies may be more exposed to wind and rain. Study where sunlight hits your growing space. Spend a day at home watching the patterns of sun and shade as the day progresses.
Even if you have only a small yard, you can increase your growing capacity by using containers. Because they're mobile, you can “go vertical” and put them on shelving or place them in spots that would normally be impractical as a growing space. Think creatively
about where your containers can go.
Most plants, properly cared for, will do well in a container for a while at least, but they may require extra attention to keep them healthy. From personal experience, I recommend firm resolve and objectivity during the plant-selection phase. It can be easy to talk yourself into attempting to grow a cactus on a shady patio or a fern on a baking-hot balcony. In the end, both you and the plant will be unhappy with the situation.
When planting in containers, choose an appropriate potting mix. Soil pulled from your yard or garden will likely be too dense. Commercial potting mixes contain perlite and other porous ingredients that enhance aeration and drainage. If you fill a container with garden soil, the soil will settle over time and become compacted, eliminating pore space.
I have seen container gardens that incorporate old charcoal grills, rubber boots, teapots, pasta colanders and paint buckets. If it can hold soil and you can make a hole in the bottom, it can be a planter. For food production, look for food-safe containers. Certain plastics, metals and even woods may leach small amounts of chemicals. This may not be a problem with an ornamental plant, but it is undesirable for edibles. Otherwise, you are limited only by your imagination. Of course, no one will criticize you for just using terra cotta pots.
Compared to in-ground gardening, container gardening presents a few unique challenges, Plants in containers tend to need more frequent watering. Extreme weather conditions also take more of a toll. Plants in containers are more exposed and can't rely on the warmth and water reserves that soil-grown plants can access. In winter I move most of my potted plants against the house to a provide a little more shelter and warmth. Keeping them well watered and covered with frost cloth is also important during harsh winter nights.
One aspect of container planting that caught me by surprise is the issue of water quality. Over time, minerals in the water build up in the soil, sometimes to excess. This buildup is more likely when a plant is not getting thorough watering. To prevent the buildup, deep-water container plants occasionally, watching for water to flow from the bottom of the pot. This tactic will help flush out excess salts and minerals.
If you have a garden hose fed by an in-home filtration system, you may not experience mineral buildup. But if you are using softened water, you may have more problems than expected. Water softeners add salts, which quickly affect plants. One sign of excess salts and minerals in a container is a whitish crust on the soil surface.
I see this buildup in my houseplants, which are lightly watered and never exposed to rain. Poor plant health also signals soil problems. Excess salts can cause a pH imbalance, which can keep the plant from absorbing nutrients. Adding fertilizers, which contain salts, may only make the problem worse. In fact, fertilizer can also build up in containers and should be occasionally flushed as well.
Container gardening offers flexibility and the potential for creativity. It's a hobby anyone can enjoy.
Workshop: Napa County Master Gardeners will hold a workshop on “Culinary Herbs and Cocktail Garnishes” on Saturday, June 23, from 9:30 a.m. to 11:30 a.m., at Central Valley Hardware, 1100 Vintage Avenue, St. Helena. The workshop will be repeated on Sunday, June 24, from 1 p.m. to 3 p.m., at Yountville Community Center, 6516 Washington Street, Yountville. Plant a plethora of herbs to add color and delight to your plate and to your beverages. Cilantro, basils, thymes, mints and their flowers, nasturtiums, roses, pansies, borage and calendula are only the beginning. Learn to grow these useful plants. Demonstrations and hands-on activities add to the fun. Online registration (credit card only); Mail-in/Walk-in registration (check only or drop off cash payment). To register for the Yountville workshop, call the Parks & Recreation Department at 707-944-8712 or register online.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
By Barb Whitmill, U. C. Master Gardener of Napa County
Spring and fall are opportune seasons to plan and create a new garden. On Saturday, February 25, U. C. Master Gardeners of Napa County will host a public workshop on drip irrigation and garden design (details below). Please plan to attend if you are plotting a new landscape or revamping an existing one.
Landscape design involves organizing outdoor spaces using both hardscape (such as walkways and walls) and plants to create a functional, attractive environment. Well-designed gardens serve their intended purpose, while minimizing the use of water, fertilizer, pesticides and labor.
Before creating your garden plan, do a site assessment. This analysis is important whether you are reworking an old garden space or starting fresh.
Evaluate the natural topography of the site: its hills, slopes and drainage. Study the sun and wind exposure in different areas. Map out existing structures such as a home, garage, pool, fences and walkways and how they are oriented to the sun.
Determine the water source for the irrigation. Locate mature trees and large shrubs that you intend to keep, and note the sun and shade patterns they create. Look beyond the property to consider views you may want to enhance or screen out.
What is your objective for the landscape and how will you use it? Perhaps you want to create an inviting entry to your home or a play space for young children. Maybe your wish list includes an ornamental or edible garden, an area for entertaining, a cooking space, a water garden, a potting shed or storage area. Consider traffic flow, how people will move from space to space. Note any concerns about loud neighbors or road noise.
Now comes the fun part, using design principles to create your landscape. Professional designers think about scale, balance, perspective and unity.
A tree planted next to a large house needs to be big when mature to fit the scale of the house.
Balance can be symmetrical—a house with identical plantings on each side of the front walk—or asymmetrical. You create asymmetrical balance if you plant a large tree on one side of the walk and several smaller shrubs on the other side.
Perspective tricks can help you visually enlarge your garden. Strong foliage colors and textures, tapering walkways, flowerbeds that draw the eye outward or “borrowing” a view beyond the property line all make a space appear larger.
Unity can come from repeating geometric shapes or design elements. For example, designing a curved lawn border for front, side and back yards will create unity.
Simplicity provides impact. Better to use a few plants in groupings rather than a lot of plants in singles. Defining the transition between plantings will create harmony.
Drip irrigation is suitable for all kinds of plantings: vegetable gardens, flower gardens, shrubs and both fruit trees and ornamental trees. Drip irrigation is efficient with little water lost to evaporation or runoff. It can be applied only when needed, and it limits weed growth as the water is supplied only to the plant. And drip lines and emitters can be easily repositioned when you move plants.
However, drip systems are not problem-free; they require monitoring and maintenance. Emitters may clog and you may not be aware that a plant is dry until it's too late. Also, drip systems can be damaged by animals, insects and humans.
Choose plants that are adapted to our climate and group them in “hydrozones” according to water needs. Each hydrozone should have its own valve that you can control individually to meet the needs of the plants in that zone. Many gardens have four hydrozones: routine irrigation, reduced irrigation, limited irrigation and no irrigation other than rain.
Most likely, your drip system will have a control center with multiple valves, a pressure regulator, a filter and a timer. Transmission to the planting area is usually constructed with PVC pipe or PE (polyethylene) hose. Emitters can be attached directly to the PE hose, or narrow tubing can be used to reach plants with emitters or sprayers. Drip tape, pierced with small holes, can be used for plants grown in tight rows, as in many vegetable gardens.
Drip emitters deliver water at a specific rate, usually one to three gallons per hour. Knowing the water needs of each plant will enable you to choose the proper emitters. Once the system is in place, each valve timer can be programmed to deliver the necessary amount of water to each hydrozone.
Anyone can learn to install a home drip-irrigation system. If you're planning a new garden or simply want to do a better job of managing your existing drip system, please attend the Master Gardener's upcoming drip-irrigation workshop.
Workshop: U.C. Master Gardeners of Napa County will host a workshop on “Drip Irrigation and Garden Design” on Saturday, February 25, from 9 a.m. to 11 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Learn how to use drip-irrigation components in your home garden in this hands-on workshop. Online registration (credit card only); Mail-in registration (check only or drop off cash payment)
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.