By Susanne von Rosenberg, UC Master Gardener of Napa County
If you're like most gardeners, you always enjoy learning something new. I recently started learning about mast seeding. I already knew that oak trees tend to have light crops some years and heavy crops other years, but I didn't realize that many other trees do the same thing.
According to the Encyclopedia Britannica, mast seeding is defined as “the production of many seeds by a plant every two or more years in regional synchrony with other plants of the same species.” Even in mast years, the plant produces seed, but there is an obvious difference in seed production between a mast year and a regular year. Mast seeding occurs on every continent except Antarctica, and the regional synchronization can extend thousands of kilometers.
What fascinates me about mast seeding is that trees (or other plants) of one species are all on the same schedule regionally and that botanists still don't know why mast seeding evolved. We know a lot about how mast seeding affects the forest ecology but only have theories about why trees and other plants behave this way.
One theory is predator satiation. If a group of plants produces a huge number of seeds, perhaps predators (hungry squirrels, birds or humans, for example) will miss some because there is so much to eat. That means that every few years, some seeds will survive and reproduce. If trees were to produce an even, but smaller, number of seeds every year, predators might eat them all.
Another theory is that mast seeding is climate driven. Certain weather conditions are favorable to ripening seeds, and the trees detect those patterns and behave accordingly.
A third theory is that trees need to store up sufficient carbohydrates in their roots to support seed production. This theory was previously considered unlikely because mast seeding is a regional phenomenon. If carbohydrate storage is the trigger, then trees that are in prime growing locations with plenty of light and water should be able to store more carbohydrates and produce seed more often than trees in shadier or drier locations.
More recently, however, science has shown that trees are linked by mycorrhizal fungi networks that allow them to exchange carbohydrates. Mycorrhizal fungi form a symbiotic relationship with trees. They colonize the tree roots and receive carbohydrates while providing nutrients and water from the soil. Mycorrhizal fungi extend much farther than a tree's roots. So the third theory is potentially valid again.
A fourth theory is that mast seeding makes for more efficient pollination. Most mast-seeding plants are wind pollinated; when more pollen is released, the odds of fertilization increase. It's nice to know that we still have a lot to learn about plants.
Fortunately, we don't have to know why plants mast seed to understand the effects on ecology. Many animals, including large creatures such as bears and hooved mammals, rely on mast seeding, as do many small rodents and birds.
Because mast seeding is irregular and relatively unpredictable, studying the response of wildlife is challenging. Until recently, researchers assumed that a bumper crop of seeds would increase the breeding success of small mammals (mainly rodents) and attract more birds. Consequently, larger animals would also be drawn to the area due to the greater availability of prey.
A meta-analysis covering nearly 200 other studies found the expected response for small mammals and birds but found that larger predators were not necessarily drawn into a mast area, most likely because they have access to a large habitat.
Mast seeding isn't limited to acorns and nuts. Bamboo is also subject to mast seeding. One generation of bamboo can live up to 100 years before all the bamboo in the same vicinity flowers and dies in the same year.
Other plants that are considered mast plants include American persimmon, coffee berry, the dogwood family, the buckeye family, Mariposa manzanita, the mulberry family, blueberries and the elderberry family.
To create more effective habitat in your garden, you can plant mast-seeding plants in a hedgerow or small wooded area. If you keep chickens or pigs, you can improve their diets by planting mast-seeding plants. And if you like to birdwatch, a mast-seeding year may increase your chances of seeing interesting birds.
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By Cindy Watter, UC Master Gardener of Napa County
Not long ago I wanted to work in my yard but the noise from a project next door was unbearable. So I went inside and looked for some gardening books to get a few ideas and perhaps even some inspiration. Rather like Goldilocks, I was looking for a book that was "just right."
Katherine White, with her essays about gardening in a New England climate, didn't work. Neither did Gertrude Jekyll, with her imperious tone that was propped up by a legion of gardeners. I finally pulled down a book by a writer I had found in the 1970s: At The Gentle Mercy of Plants by Hildegarde Flanner.
I first discovered Hildegarde Flanner from an essay in The New Yorker entitled "Wildfire: Berkeley, 1923." Years later, I found the essay again in the above-mentioned book, which is still in print. Flanner, who spent the last 25 years of her life in Calistoga, was originally from the Midwest. She was the youngest of three daughters and moved with her mother to California after her father died.
One of her sisters, Marie, moved to New York to teach music. The other, Janet, became the celebrated "Letter From Paris" writer for The New Yorker. Hildegarde Flanner was not as famous as her sister (or her husband, the architect, artist, and teacher Frederick Monhoff), but she was a wonderful writer and poet who deserves to be better known.
According to a firefighter the Flanners met after they returned to their destroyed house, the Berkeley wildfire was started by a power line igniting a grass fire in Wildcat Canyon. Flanner's description of the dry weather, the wind and the smoke, as well as the feeling of alarm and helplessness, sounds familiar to many of us in Napa. After losing the house in Berkeley, Flanner lived in Pasadena with her mother and husband, and they endured several more fire evacuations.
One might wonder why they continued to live in an area that was so vulnerable. Her answer is that fire is part of the western landscape. "It is in the earth,” she wrote. “It is in the air. It is rooted in the chaparral. It lies ready to leap up from the yellow grass of summer. During the rainless months it is a dread, a menace, and we never forget it. It is fire. We fear it and we hate it, but we settle our lives and our homes in its territory because that is where the excitement of beauty is naturally established—the richest views, the loveliest valleys."
Flanner became profoundly attached to the places she lived, and her gardens were a big reason why. In Pasadena, she said the early missions influenced garden layouts, with square beds surrounded by pathways. She filled her beds with "a rabid jungle of plants madly embracing each other and suffocating their mates out of existence." She favorited flowers and fruit trees of staggering abundance.
Flanner had a gardener/handyman who was perhaps the earliest adopter of the sharing economy. He moved people's plants from one home to another, depending on who needed them more. No one seemed to mind.
In her essay "Gentle Aliens: A Strolling Conversation," Flanner described the semitropical exotic trees that have been introduced in California as being so numerous that instead of altering the environment, they have become the environment. She goes into some detail about the eucalyptus, which was brought to San Francisco from Australia by a Mr. Walker, in 1855. It became so ubiquitous that many people thought it was native. The introduction of exotic trees became a craze in California and is exemplified in Napa by our own Fuller Park.
After engaging in battle with an invasive bamboo a few years ago, I am not a fan of the plant, but Flanner's essay "Bamboo: An Honest Love Affair" might make me rethink that attitude. She loved bamboo and planted many different kinds when she lived in Napa County. Flanner appreciated bamboo's history. It has provided food, building material and artistic inspiration. It is also beautiful.
Hildegarde Flanner's writing creates a sense of place. I feel as if I have been launched into her personal landscape when I read her work. She helps me appreciate where I live.
If you would like to learn more about trees in Napa, or keep a record of your own gardening efforts, check the UC Master Gardeners website for our guide to local trees and our month-by-month gardening guide.
Napa Library Talk: “Cool Tools and Gifts for Gardeners” on Thursday, December 3. Register to get Zoom link. http://ucanr.edu/wildlifehabitat2020
Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to email@example.com or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email.
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by Penny Pawl, U.C. Master Gardener of Napa County
Oh no, I've done it again. I have fallen in love with a plant and its beautiful flowers. I planted it; it grew well and then I discovered that it is on the invasive plant list. What to do? And why is this plant on the list?
Many of the wonderful plants that I have planted over the years are on this list. How do authorities create this list? Some of those plants include pampas grass (Cortaderia jubata), mullein (Verbascum),butterfly bush (Buddleia davidii), Watsonia and privet (Ligustrum spp).
Most gardeners are aware that bamboo is invasive. Years ago, my husband and I planted bamboo in a wine barrel. Because we knew it had a spreading habit, we set the barrel on cement blocks. A few months later we noticed that a stem had come out the bottom of the barrel and was inching its way across the soil toward our house. Bye bye, bamboo.
Scotch broom (Sarothamnus scoparius) is probably the most notorious problem plant. It has taken over entire areas of our state and moved up the coast into Washington. It is also a problem in many other states. I have read about groups going out to remove this plant from parks and other wild areas.
Scotch broom spreads by the root system. The roots have nitrogen-fixing bacteria so the plant grows all year. It also produces large amounts of seed. If left alone, it will take over and crowd out native plants.
Pride of Madeira (Echium candicans) is native to the island of Madeira. I visited there a few years ago, saw the plant and fell in love with its tall purple spires. I planted one about two years ago. It has grown well and has not needed water or care. It bloomed this year, and the bees and other pollinators were in heaven.
Before I planted more, I decided to check its status. Alas, it is also on the California list of invasive plants. Each one of those little purple flowers produces lots of seeds which take root easily in our soils.
I do not plan to remove it, so I went out one evening as the flowers faded and before the seeds set, and cut it back. I did it at that time of day to avoid the bees and other insects. I will need to repeat this every year to keep pride of Madeira from becoming a pest in my garden and my neighbors' gardens.
A couple of years ago I snipped two pieces of honeysuckle (Lonicera) and rooted them. They are now in barrels growing up a big trellis. When I looked for more information on this plant, which is currently in full bloom, I discovered it, too, was considered invasive. Like pride of Madeira, it produces many seeds and pollinators love it. I have to trim it after flowering to keep the seeds from spreading. It also spreads when long runners touch the ground and take root.
The California Invasive Plant Council (Cal-IPC) list has been around for many years. If you are serious about preventing the spread of invasives, you should check the list before planting. You can find it on the Cal-IPC website along with photos to help with the identification.
Some of the plants in the weed category came in with New World settlers. The weeds were hitchhikers. Others such as Scotch broom were brought in because they grew so well in their native areas.
What do these plants all have in common? They are generally drought tolerant, and they produce massive amounts of seed. Birds love the seeds and spread them far and wide. Some invasive plants, such as wisteria, spread when their branches touch the ground and take root, or their root system moves around seeking water. When I trim the flowers of invasive plants, I don't put them in my compost. I put them in my brown yard-waste bin so they can be hot-composted by the city.
If, like me, you have a beautiful invasive plant growing in your garden, take care to keep it from taking over the whole garden. Otherwise, be safe and replace it with a native plant instead.
The UC Master Gardeners of Napa County are volunteers who provide University of California research-based information on home gardening. To find out more about home gardening or upcoming programs, visit the Master Gardener website (napamg.ucanr.edu). Our office is temporarily closed but we are answering questions remotely and by email. Send your gardening questions to firstname.lastname@example.org or leave a phone message at 707-253-4143 and a Master Gardener will respond shortly./span>