By Daniel McLoughlin, U. C. Master Gardener of Napa County

Most Napa Valley gardeners have long embraced the idea that planting native species is the way to go. These locally evolved species tend to be more acclimated to our long, dry summers and less thirsty as a result.

But there is growing evidence that native plants do far more than just save water. A study by scientists at the University of Delaware and the Smithsonian Migratory Bird Center, recently published in the journal Biological Conservation, underscores another way that native plants can support local ecosystems in urban and suburban settings.

The study was conducted over a four-year span. The observation team identified where breeding birds foraged for food in the yards of 203 homes in the Washington, D.C., metropolitan area. They documented which plants provided the most bird food, such as insects and caterpillars.

Among the findings were that native plants provided more caterpillars than non-native plants, that the birds preferred foraging in native plants and were more likely to breed in sites with native plants.

While these findings may be limited to the specific parameters of this study, the idea that the natural world is deeply interconnected comes as no surprise. We now understand that most insect species evolved over time with a specific plant species or group of plants.The insects adapted to the chemical defenses of its host plants.

Often these adaptations are very precise. Caterpillars, an important food source for birds, tend to be picky about what they eat. For instance, the Monarch butterfly larva must have milkweed (Asclepias fascicularis) to survive. Most insects and animals avoid milkweed because of the toxins and latex it secretes, but the Monarch has adapted to it. In fact, the Monarch will only lay its eggs on milkweed. Without milkweed along its migratory path, the Monarch cannot reproduce and the creatures that feed on Monarch caterpillars must look elsewhere for a meal.

Last year, the Audubon Society launched the Plants for Birds program, which encourages and provides resources for people to support birds by planting native species (http://www.audubon.org/plantsforbirds). The site also provides a database by zip code that helps to identify local native plants and the types of birds they tend to attract (https://www.audubon.org/native-plants). 

According to the Audubon Society, the human-dominated landscape “no longer supports functioning ecosystems, and the remaining isolated natural areas are not large enough to support wildlife.” This situation is the result not just of urbanization and expanded agricultural production, but also of our desire for manicured lawns and exotic ornamental plants. Research by the entomologist Doug Tallamy has shown that native oak trees support over 500 species of caterpillars, whereas the gingko, the commonly planted and beautiful landscape tree from Asia, hosts only five species of caterpillars.

ReScape California, also known as the Bay-Friendly Landscaping & Gardening Coalition, is a resource for those who want to learn more about incorporating biodiversity into their landscape. Among its guiding principles are water and energy conservation, improving the “soil food web” and reducing the landscaping impact on landfill.

In this organization's view, maintaining a Bay-friendly landscape means recognizing that “biodiversity is crucial to the health of natural ecosystems and that by using native plants and increasing the diversity of plant palettes, our built landscape can provide food, water and shelter for birds, butterflies, beneficial insects and other creatures.”

According to U.S. Census data, there were nearly 66,000 people living in Napa County in 1960. By 2010 the county's population had more than doubled. That increase mirrored the growth of the Bay Area as a whole, which almost doubled in population in those five decades. Our ancestors needed space to live, just as we do, and so will those who come after us.

I fuss over my lilacs because they demand it and because I love them, but the fact is, they contribute almost nothing to everything else that lives in my yard, or might want to live here. Nothing ever eats them. The same goes for the Australian tea tree, even though it's never thirsty.

I'm not going to pull these plants out, not yet anyway, but the next time I have the chance, I'm going to think about the birds and the bees and the caterpillars. After all, I'm not the only one who lives here.

Workshop: U. C. Master Gardeners of Napa County will host a workshop on “Rose Pruning” on Saturday, January 13, from 10 a.m. to noon, at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Why do we prune roses? Is winter the only time to do it? What will happen if we don't? Should hybrid teas be pruned differently from floribundas? Join the Master Gardener Rose Team at this popular forum where resident experts will answer your questions about basic rose pruning fundamentals with research-based information. Topics include rose types, how and when to prune, what tools to use and how to care for them, safety and sanitation.  No doubt each Master Gardener will have some suggestions for new plantings, too. Online registration (credit card only);Mail-in/Walk-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.

By Iris Craig, UC Master Gardener                                      

Many residents of Napa Valley are continuing to recover from the October wildfires. These horrific fires killed people and animals, devastated homes and gardens and left the ridges above our valley scarred and bare. Thanks are due to the first responders for all that survived. My neighbors, friends and I are just beginning to imagine a different, healed and beautiful landscape with new and repaired homes.

I find myself wondering why some homes survived and others did not. Outbuildings, garages and studios burned to the ground, but some of the nearby houses themselves survived.

How did some landscapes remain untouched or minimally damaged? A friend told me that her house was untouched by the flames, but her front yard burned to the concrete porch where the fire stopped.

Why is this possible? How can we prevent this tragedy from happening again? What do research and personal experience tell us about designing our future landscape?

A wildfire requires a source of ignition. Once ignited, it needs fuel to spread. The gusting winds in early October contributed to the rapid spread of three fires in our area. Despite the wind and the moving flames, some areas survived. Why?

We can look for answers in the dynamics of wildfire: the need for fuel to feed the fire; and the tendency of fire to move upward. You can see this in the burn areas along our ridges and at the top of the hills. This is why flames ladder up trees and burn in the canopy. With good landscape choices, we can thwart the rapid movement and intensity of fire.

The aim of fire-wise landscape design is to create a defensible space. Assess your site. What are the elevations? Is your home near the top of a hill or a cliff? Do your home and outbuildings border a heavily wooded area? Or are they in an urban area, close to other homes, with trees?

Many of us thought we would not be touched by the fire because we lived in the city. However, the devastation of a Santa Rosa neighborhood demonstrated that we are not safe. We all need to think about fire-wise landscaping.

Determine how much defensible space you need for your home. California law now requires that homes have 100 feet (or to the edge of the property) clear of forest debris with tree crowns spaced 100 feet apart. If you live on a hilltop or ridge, you need an additional 50 feet on the downside of your property, with a recommended six feet between plants.

Next to lack of defensible space, flying embers are the greatest threat to homes and surrounding vegetation. For this reason, any heavy equipment used in fire-vulnerable areas is required to have spark arresters for fire prevention.

Cal Fire (the Department of Forestry and Fire Protection) recommends keeping the 30 feet nearest your home as a “lean, clean and green zone.” No trees or bushes should touch the buildings. Any plants or trees in this space should be those identified as less likely to burn quickly.

Many of us have created water-wise landscapes, eliminating grass, installing drip systems and topping the ground with various types of mulch. Some mulches can ignite quickly from embers.

The University of Arizona Extension studied the flammability of mulches. The least flammable were stone and aggregated granite. Researchers ignited several types of ground cover including straw, wood chips, shredded bark, garden mulch and bare ground. Hay ignited quickly. Bare ground, garden mulch and shredded bark proved less likely to ignite and are considered appropriate for a fire-wise landscape. Hardscapes, including walkways and retaining walls, also tend to thwart a low-burning fire.

Tall grasses; bushes planted in a row; chunks of bark; wooden fences; piles of firewood or debris; or a butane tank with tall grass beneath it are all vulnerable to ignition by embers. Clustered, low-fire bushes; grasses; shredded bark and native plants under four inches tall reduce the fire risk.

California fire code requires keeping the next 70 feet around the home as a reduced fuel zone, with all logs and stumps removed. It's okay to preserve one standing dead tree per acre to support wildlife. If it should fall, it must not touch buildings or roadways. Keep plants under trees small and watered as needed. Prune trees to create a six-foot vertical gap between trees and shrubs to discourage the laddering of fire.

With science-based information, we can begin to create a fire-wise landscape. We move forward, step by step, to recreate our gardens and homes and protect ourselves, as much as we can, from the ravages of fire.

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 Cindy Watter, U. C. Master Gardener of Napa County

One of the attractions of my house, when I first saw it for sale some decades ago, was a fragrant, lush Meyer lemon tree, abloom in the side yard. Unfortunately, by the time I moved in, the Great Blue Norther of 90/91 had transformed it into a blackened mass of lifeless twigs and shriveled leaves.

The previous owners had neglected to cover it at night, and the unusually cold weather that winter had done its malign work, killing the tree. It actually looked as if it had been scorched, not frozen. I learned that the plant cells had solidified in the cold, which meant that the nutrition cycle had been blocked. The lemon tree appeared deflated, which was exactly how I felt at the time.

The best way to protect your plants during an unusual cold spell is through preparation. Assume it will freeze sometime this winter. (It only takes one night to do major damage.) Pay attention to weather reports. Identify which plants need protection. Assemble a collection of old sheets, blankets, towels, burlap, cardboard boxes, baskets and/or buckets. Do it now to avoid the horrid midnight rush to save the avocado (when it's probably too late anyway).

What plants will need attention? Young fruit trees with thin bark, avocado trees and citrus trees are the main candidates in Napa Valley. Certain tender shrubs, such as brugmansia, fuchsia, mandevilla, daphne and bougainvillea should be covered. Some cacti and succulents need protection. If you have plantings in a lower elevation of your yard, these plants should certainly be protected, as those parts of a yard are always a few degrees colder than the rest of it.

Water the plants before you cover them, which should be before dusk (except for succulents). Some of the water will evaporate during the night and warm the surrounding air.

For small plants, you can fill old plastic milk jugs with water, which will insulate the plants a bit, and then use those vessels to support a draped cloth.

Small plants will do fine with an overturned bucket, cardboard box or basket for protection. If you have a lot of small potted plants, move them to a protected spot or next to a wall. You can also protect small plants by covering them with mulch.

If you use a sheet or a blanket as a cover, it shouldn't touch the plant. You can build a frame to support the cloth, or create your own supports with lawn furniture, clothes drying racks, trellises or bean poles. If the cloth touches the plant, it can transmit cold, so use a frame. Make sure the cloth reaches the ground, for better insulation. Remove the cloth in the morning, after the air warms up.

You can wrap young tree trunks with burlap or old blankets or towels for insulation.

Nurseries sell plant covers in all sizes and shapes, including row covers. They are made of a nonwoven synthetic, and they allow light to penetrate so you can leave them on during the day. This fabric—similar to the interfacing used by home sewing enthusiasts—can touch a plant's leaves without doing harm.

If the worst happens and your plant freezes, don't lose hope. It just might recover. I thought I had killed two large brugmansia shrubs last winter. A surprise freeze had left them drooping and shriveled.

I consulted Sunset's Western Garden Book and learned that, instead of hacking the shrubs down to the ground or throwing them out, I should wait until spring to see if any new growth occurred. And it did!

At that point, I pruned the brugmansia down to the green leaves, put them in large pots (so I could move them near the house in the winter) and saw them put forth spectacular peach-colored trumpet-shaped flowers in late summer. They are so sturdy they even survived a walnut limb landing on them and being blown over by the windstorm that preceded the October wildfires.

When spring returns, rethink some of your plant placement. Perhaps you have citrus trees in planters. You could put the planters on wheels and roll the trees to a sheltered spot during cold spells. Maybe you should move plants that are in sunken areas of your yard.

A fragile plant can be placed against a south-facing wall, and the warmth that radiates from the wall will help the plant get through the winter. I have noticed how many bougainvillea are trained against south walls in Napa Valley. That's where my new lemon tree is, and it has survived several cold spells.

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.

Chances are that by now you have one or more cuetlaxochitl somewhere in your home. You may not recognize the name, but they have recently spread across Napa. Don't call an exterminator yet, however.

Cuetlaxochitl, more commonly known as poinsettia (Euphorbia pulcherrima), are the popular red-leafed plants used as decoration around the holidays. The story of the poinsettia is an interesting one.

Native to Central America, these plants were originally used by the Aztecs to create red dye as a medicine to reduce fevers. Their association with the holiday season goes as far back as the 16th century, when Spanish monks integrated them into their Christmas traditions.

They were first brought to the United States by Joel Roberts Poinsett in the 1820s. Poinsett was the first ambassador to Mexico, a congressman and co-founder of what we now know as the Smithsonian Institution. Botany was always a subject to his heart, and he could not resist the plant's bright red foliage.

Poinsettias did not become the ubiquitous holiday decorations they are today until nursery owner Paul Ecke, Jr., made a concerted effort to popularize them in the 1920s. The Ecke family discovered a poinsettia-growing technique that allowed for the development of the full, bushy plants we have today.

Ecke developed shipping and distribution methods that allowed him to spread his plants across the country in good condition. He also sent samples of his plants to television shows for holiday specials, obtaining free advertising as well as cementing the poinsettia's association with the holidays. The Ecke family kept their growing method a secret until 1991, when it was independently rediscovered and shared with other nurseries.

Other tropical plants that have become holiday favorites are those of the genus Schlumbergera, holiday cacti. Native to Brazil, where they are often referred to as "Flor de Mayo" (May flower), these cacti are different from others. Instead of preferring sunny, arid conditions, these plants thrive in shady, humid environments. They are also epiphytic (growing on trees) or lithophytic (growing on rocks).

Most species have flattened, segmented stems that are often mistaken for leaves. The stems have actually evolved to function similarly to leaves, performing the necessary photosynthesis for the plant. You may have heard some of these plants referred to as "Christmas cactus;" you may not have known that there is also a "Thanksgiving cactus." The former is identified by thorny points along its stem segments, while the latter has smooth, rounded segments.

Holiday cacti were first induced to England in the early 1800s by botanist and explorer Allen Cunningham. He "discovered" the plants while on an expedition to Brazil for the Royal Horticultural Society. They were quickly adopted into Christmas traditions almost entirely due to the fact that their bloom time coincides with the holiday. Their immense popularity resulted in the development of large amount of cultivars, most of which have since been lost.

Mistletoe (Viscum album), another holiday decorative staple, has a much longer association with the holidays. As the plant blooms in the winter, the Druids saw it as symbolizing the vigor of life, often using it to bring luck to ward off evil. Norse mythology, depending on the tale, uses mistletoe as a symbol to remember that which was forgotten, or as an emblem of love and friendship.

Sometime in the 18th century, mistletoe became part of Christmas traditions in England. People adorned doorways with mistletoe, with the custom of allowing those beneath to "steal a kiss.” Each time a kiss occurred, a berry was to be plucked from the mistletoe; when the berries were gone, the kissing was to cease.

Interestingly, Viscum album is a primarily parasitic plant. It performs very little photosynthesis on its own, but instead grows roots in an unsuspecting host plant. These roots draw nutrients from the circulatory system of the host, providing the mistletoe with all it needs to survive.

While mistletoe has some medicinal uses, it can also be toxic, causing heart rate changes and gastrointestinal problems. The association of a parasitic, potentially toxic plant with the concepts of love and friendship is an ironic one indeed. It is, at least, a useful conversation item should you need to dodge an undesired pair of lips this holiday season.

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.