- Author: Help Desk Team
Are you a gardener with questions? Are you a beginning gardener just getting started? Do you want to know more about how to troubleshoot problems in your garden? Some of the topics addressed in our classes and material cover what, when, and how to plant, how to prepare the soil, and maintenance of your plants, including pruning.
The Contra Costa Master Gardener website (https://ccmg.ucanr.edu/) has links to information about both edible gardening and landscape gardening. We also offer a program called Vegetable Gardening for Beginners if you are interested in growing vegetables: https://ccmg.ucanr.edu/GrowingGardeners/
This is the handbook for this class: https://ucanr.edu/sites/ccmg/files/292083.pdf
There are many resources online through the University of California that can provide you with good information about specific pests and diseases, including the following:
• Home, garden, turf, and landscape pests: https://ipm.ucanr.edu/PMG/menu.homegarden.html
• UC California Garden Web: https://cagardenweb.ucanr.edu/
These are the books the Master Gardeners use for training and reference:
• The California Master Gardener Handbook: https://anrcatalog.ucanr.edu/Details.aspx?itemNo=3382
• Abiotic Disorders of Landscape Plants: https://anrcatalog.ucanr.edu/Items.aspx?search=abiotic%20disorders%20of%20landscape%20plants
• Pests of Landscape Trees and Shrubs: https://anrcatalog.ucanr.edu/Items.aspx?search=pests%20of%20landscape%20trees%20and%20shrubs
• Pests of Garden and Small Farm: https://anrcatalog.ucanr.edu/Items.aspx?search=pests%20of%20the%20garden%20and%20small%20farm
The UC Master Gardener volunteers of Contra Costa County are actively involved in bringing you educational programming. We partner with the Contra Costa County Library to present topics that will help you grow a healthy, thriving and sustainable garden. See the upcoming and past webinars here: https://ccmg.ucanr.edu/Webinars_and_Programming_/
You can find a schedule of in-person talks at libraries, at our Walnut Creek demonstration garden, and when Master Gardeners will have tables at Farmers Markets where you can ask questions at this link:
https://ccmg.ucanr.edu/Find_Us/Find_Us_by_Location/
You can also find past webinars as well as short, single-topic videos on a wide range of gardening topics on the Contra Costa Master Gardener Program YouTube channel: https://www.youtube.com/@CoCoMGUC
Still have questions? Send an email to the Contra Costa Master Gardener Program Help Desk: ccmg@ucanr.edu
• Include your name, phone number, and city.
• A description of the problem, including the name of the plant, when the problem began, and cultural history such as water, fertilizing, pruning, pesticides, etc.
• Photographs are very helpful. Include photos of the problem parts, but also photos of the whole plant.
Help Desk of the UC Master Gardeners of Contra Costa County (SEH)
- Author: Ben A Faber
Florida's citrus industry has long been susceptible to freezes, hurricanes, and disease. A series of devastating freezes in the 1970s and 1980s caused production to shift to more southern regions of the State. Then after near-record output in the 2003/04 season, subsequent events decreased Florida's orange output at an average rate of 6 percent a year. Between 2004 and 2005, 4 hurricanes reduced the size of the orange crop and further spread citrus canker, a bacterial disease damaging to tree health and fruit quality, to previously unaffected areas. The Florida citrus industry faced an additional challenge in 2005, when citrus greening disease, a bacterial disease deadly to citrus trees, was first detected in its commercial groves. Citrus greening disease leads to premature fruit drop, unripe fruit, and eventual tree death. With no known cure, citrus growers use a variety of management strategies to protect young trees, increase tree immune response, sustain grove health, and improve fruit marketability. While these management strategies can partially offset yield losses, they increase the costs of production. Hurricanes in 2017 and 2022 dealt further damage to Florida's citrus industry. Since 2003/04, bearing acreage of Florida's orange trees has declined at an average rate of 3 percent per year. In April 2024, USDA forecast Florida's orange 2023/24 production at 846,000 tons, 19 percent higher than the previous year but the second-lowest harvest in nearly 90 years. This chart updates information in the USDA, Economic Research Service Fruit and Tree Nuts Outlook, published in March 2023.
From USDA: https://www.ers.usda.gov/data-products/chart-gallery/gallery/chart-detail/?chartId=109051
- Author: Elinor Teague
It's so nice to have a lush garden again (however short the time until drought resumes) but the vigorous plant growth will cause problems this summer.
Plants and trees that have suddenly outgrown their spaces this spring will obviously need to be trimmed back, but the trimming and pruning should not be a one-time major cut back. Reducing the size of the leaf canopy by more than 25 to 30 percent during the growing season removes too much of the plants' and trees' sources of energy and can cause stunted growth. A light pruning using thinning cuts to reshape the outer canopy of only those branches that are obstructing access or that risk causing property damage would be best during the summer. Leave the removal of larger branches and branch scaffold restructuring until winter when deciduous trees are dormant.
The recent overgrowth on many plants will have shaded the soil underneath the larger canopy as well as the roots that extended to the edge of the enlarged canopy. Those roots may well die back in the hot soil. Expect to see some wilting and signs of heat stress after even moderate pruning.
The second caution on pruning overgrown plants this summer involves the risk of sunburn on newly exposed interior wood. We can expect that the Central Valley will experience several heat spikes, or long periods of high daytime temperatures (above 100 degrees) along with warm nighttime temperatures, in the next few months. Sunburn is a common problem on hedges that are pruned heavily during the summer in the Central Valley with the hedge tops showing most of the damage from the sun's rays. It's best to shear hedges lightly and frequently, every six to eight weeks, in the summer. To help reduce damage from sunburn, use a mixture of half water/half white latex paint on exposed wood, especially on citrus and other fruit and nut trees, to reflect some of the sun's harsh rays. The open center or vase-shaped pruning system on most fruit and nut trees should be maintained in the summer months.
The UC ANR publication 8057 on pruning deciduous trees has line drawings of several pruning methods and a glossary of pruning terms, which provide very basic pruning information. A long time favorite pruning guide, Orthos' ‘All About Pruning,' is once again out of print but worth searching for in used book stores for its excellent detailed descriptions, drawings and photos of the proper pruning techniques specific to many tree and bush species. DK Publishing (one of the best publishers of garden books) has “Grow Pruning and Training" ISBN 9780744026832, $12.99, which seems to be a good replacement for the Ortho guide.
- Author: Cindy Watter, UC Master Gardener of Napa County
There is a beautiful house for sale in my neighborhood, and it was recently featured in the New York Times. Among its abundant selling points is a magnolia tree. It is indeed a lovely tree, and it is in bloom right now. It has glossy blue-green leaves and on the hottest day is cool and refreshing to the eyes. I walk past it every day and admire it.
This tree is the southern Magnolia (Magnolia grandiflora). It is an evergreen magnolia, with large white blooms. I have also seen many deciduous magnolias around town, called saucer Magnolias (Magnolia soulangeana). They are smaller than the southern magnolia, which can overhang a two-story house. Saucer magnolias come in a variety of colors, but the pink ones are the ones I see most often in Napa.
The Sunset Western Garden Book says early spring is the best time to plant trees with root balls that are wrapped in burlap. Container magnolias can be planted anytime. So, if you are interested in one of these trees, which add beauty and value to your landscape, put a reminder in your gardening notebook. Magnolias need sun to flower, but they won't do well in a scorched, windswept area. They are considered excellent landscaping trees, with one caveat—grass won't grow under them, so keep that in mind.
Magnolia roots are sensitive and can be injured. When you plant your tree, it is best to set in some markers to indicate root spread. (You can remove them when the tree is established.) Dig a hole about one and a half times the size of the root ball and slightly less deep. You want the root cavity to be even with the surrounding ground. Add some compost, and then apply mulch. Keep some space between the mulch and the trunk—don't let the mulch touch the trunk. Depending on your soil, you may need to fertilize occasionally. If your soil is too alkaline, the magnolia leaves will yellow from iron deficiency, so use some iron chelates. Use a controlled release fertilizer for nitrogen deficiency. Don't over fertilize.
The best way to water magnolias is with a drip system that follows the root line. You should water deeply, not with superficial splashing that uses up lots of water but doesn't hydrate properly. Once the tree is established it needs less water.
Magnolias don't need much pruning. I have a friend in Virginia who never prunes her southern magnolia, and it is twenty years old, sixty feet tall, and very healthy. (She also never waters it because Virginia rains in the summer.) The best time to prune deciduous magnolias is after they bloom. Prune for shape, removing any errant branches. Evergreen magnolias should be pruned in winter before the big spring growth burst. Wear gloves if you do prune your magnolia because the juice from the tree can irritate skin.
Magnolias, biologically speaking, are an ancient tree. According to the Smithsonian Institution, they existed in the Cretaceous period, when dinosaurs roamed the earth--but not bees. Beetles pollinated magnolias then. Because of that, their evolution is unusual. Magnolia flowers have very sturdy carpels, or female parts of the flower, which mimic the stamens, which are the male parts of the flower. The petals of a flower attract pollinators, and the sepal protects the reproductive organs of the plant. Because the petal and the stamen of the magnolia are similar in size and color, the sepal is called a tepal. When the beetle came to the flower, it would roll about in the pollen, covering itself with it. In the evening, the tepal would close over the beetle. In the morning, the tepal would open and release the beetle, which would go off to pollinate another flower. This is how the magnolia achieved cross-pollination, resulting in a stronger plant that has survived for millions of years.
The fruit of the magnolia is shaped rather like a pinecone and is covered with follicles. It contains reddish orange seeds. Birds love the seeds and disperse them widely.
The magnolia is named after a French botanist, Pierre Magnol, a 17th century botanist who worked on plant classification before the Linnean system we use today. According to the Smithsonian Institution, he had an “intuitive understanding” of plant relationships because of their similar characteristics.
I find magnolias fascinating. Maybe it's nostalgia—my childhood was spent in South Carolina. Once a week an old lady would drive through our neighborhood in a Model T, with the back loaded with coffee cans full of flowers that she grew. Her name was Miss Corrie, and my mother would send us out to buy magnolia buds when they were in season. Mama would put the buds in a dish of water, and we would watch them open. As each petal unfurled, it made a tiny snapping noise. The flower had an intense fragrance with a hint of citrus. When we put the opening buds on the patio table outside, the bumble bees would literally wallow in them. I was only six, but I knew just how they felt.
Library Talk: Join UC Master Gardeners and Napa County Library for “All About Lavender,” on Thursday, June 6, from 7 pm to 8 pm, via Zoom. Have you ever wondered what you can do with that gorgeous lavender growing in your backyard? Learn what lavender needs to thrive, and harvest ideas for how to incorporate it in your own homemade creations. Register to receive the Zoom link.
Workshop: Join UC Master Gardeners of Napa County for a workshop on “Planting for Monarchs and Other Pollinators” on Sunday, June 16, from 2 pm to 4 pm, at Yountville Community Center, 6516 Washington Street, Yountville. Learn about host plants and nectar plants and how to include them in your garden. This workshop is offered in partnership with Yountville Parks and Recreation Department. Register on their website. Click Adult Activities, then UC Master Gardeners, then Planting for Monarchs and Other Pollinators.
Help Desk: The Master Gardener Help Desk is available to answer your garden questions on Mondays and Fridays from 10 am until 1 pm at the University of California Cooperative Extension Office, 1710 Soscol Avenue, Suite 4, Napa. Or send your questions to mastergardeners@countyofnapa.org. Include your name, address, phone number and a brief description.
- Author: Penny Pawl, UC Master Gardener of Napa County
When my husband and I first started gardening at our new Napa home, we made many errors. One of the big mistakes was planting invasive plants.
We really wanted bamboo, but we did know it had a reputation for taking over gardens. So, my husband put golden bamboo (Phyllostachys aurea) in a half wine barrel set on concrete blocks. A year or so later, we noticed something coming out the bottom, creeping across the soil and headed to a garden bed. We never imagined that bamboo had a mind of its own. Bye-bye bamboo.
My neighbors planted giant bamboo (Dendrocalamus giganteus) next to their front porch. It put on a beautiful show when it bloomed. And then the roots started creeping under the house. After fighting the bamboo for a while, they removed it permanently.
A retired Master Gardener, who has since moved, had a wonderful old house on Coombsville Road. On one side of her house was a magnificent old wisteria. This vine sent roots and shoots under her cement basement, and they emerged on the other side of the house.
Wisteria planted in the wrong place can indeed be invasive. I transplanted wisteria from our first house in Napa to our next home in Calistoga, then back to Napa. I still have it in my current garden, but I planted it on a fence far from structures. And I check it often for sprouts moving in every direction. Heavy pruning also helps keep this plant in check.
My husband and I planted pampas grass (Cortaderia selloana) when we first started landscaping. Those huge plants try to take over the world. It was slowly moving toward the road, so I had it removed.
Everyone loves redwood trees. They're practically a symbol of Northern California.
But they should never be planted near a home and, frankly, never in a home landscape.
I have been digging in a raised bed in preparation for planting my summer garden and guess what I found: tons of redwood feeder roots. In fact, I found one fat root that is no longer a feeder. I plan to have a helper dig up this bed. Then I will solarize the soil next summer to kill those feeder roots.
Solarization involves wetting the soil, then covering it with black plastic sheeting and letting it bake in the summer sun. The heat will also kill most weed seeds.
As I weed, I am finding baby redwoods everywhere. The winter rains encouraged the redwood seeds to sprout. And squirrels have fun throwing the seed pods everywhere.
My husband wanted trees that grew fast, so he planted a Monterey pine (Pinus radiata) near our house. They are known to grow more than six feet a year and to get just as big around as they are tall.
Within a few years this tree was indeed very big. One summer it split, and part of the tree was pointed toward the house. It was a delicate operation, but my husband and a neighbor used a pickup truck and rope to take it down. We never planted another Monterey pine.
I have also been grappling with nandina (Nandina domestica). Some varieties send out long roots that eventually decide to grow a new plant. Unless you want a nandina forest, be sure to buy the clumping type for your garden. Mine had to be dug out.
There are about 40 plants considered extremely invasive in California, and some nurseries still carry these plants. So do a little research before you buy. Most of these bad boys have beautiful flowers and do well in our soils and climates.
Scotch broom (Cytisus scoparius) is a good example. This plant spreads over large areas, pushing out native plants. We once traveled a back road at Point Reyes and for miles there was nothing but blooming Scotch broom. Native plants and wildlife evolve together, so a thuggish plant like Scotch broom can create a wildlife desert.
Some honeysuckle (Lonicera japonica) is also invasive. I have two that I propagated from cuttings. While they are in large pots and growing well, I am aware that they may have broken through the pots and rooted in the soil. They are huge and I have not tried to move them. They are growing on a screen that provides a visual barrier in my back garden, and the bumblebees love them. I am just happy that I did not plant them in the soil.
I have also, unwittingly, acquired a stand of Himalayan blackberries. I suspect that birds planted them. These vines are invasive, and I will have them taken out this summer. They are thorny and it will be a major project.
Before you bring any new plant home from a nursery, do yourself a favor and make sure it is not on California's invasive plant list. You can find this information easily online.
Library Talk: Join UC Master Gardeners and Napa County Library for “All About Lavender,” on Thursday, June 6, from 7 pm to 8 pm, via Zoom. Have you ever wondered what you can do with that gorgeous lavender growing in your backyard? Learn what lavender needs to thrive, and harvest ideas for how to incorporate it in your own homemade creations. Register to receive the Zoom link.
Workshop: Join UC Master Gardeners of Napa County for a workshop on “Planting for Monarchs and Other Pollinators” on Sunday, June 16, from 2 pm to 4 pm, at Yountville Community Center, 6516 Washington Street, Yountville. Learn about host plants and nectar plants and how to include them in your garden. This workshop is offered in partnership with Yountville Parks and Recreation Department. Register on their website. Click Adult Activities, then UC Master Gardeners, then Planting for Monarchs and Other Pollinators.
Help Desk: The Master Gardener Help Desk is available to answer your garden questions on Mondays and Fridays from 10 am until 1 pm at the University of California Cooperative Extension Office, 1710 Soscol Avenue, Suite 4, Napa. Or send your questions to mastergardeners@countyofnapa.org. Include your name, address, phone number and a brief description.