- Author: Kathy Keatley Garvey
When a newly eclosed Western tiger swallowtail, Papilio rutulus, lands on a butterfly bush, the colors are striking.
The yellow and black butterfly contrasts well on the purple blossoms of Buddleja davidii.
While the majestic butterfly is widely loved, the plant, also called summer lilac, is not. It's considered an ecological threat and a noxious weed by the Invasive Plant Atlas of the United States: "Buddleja davidii readily invades disturbed sites and riparian areas. Although butterflies will use this plant as a nectar source their larvae cannot survive on it. By replacing native larval food source plants butterfly bush can have a negative impact on wildlife."
B. davidii is native to Sichuan and Hubei provinces in central China, and also Japan. The genus, Buddleja, is named for the Rev. Adam Buddle, an English botanist. The species name honors Father Armand David, a French missionary and explorer in China, Father Armand David, who was the first European to report the shrub, according to Wikipedia. It won the RHS Award of Merit in 1898, and the Award of Garden Merit (AGM) in 1941.
Now nurseries are selling non-invasive hybrids, with such names as "Lo and Behold" and "Blue Chip" and "Flutterby."
Nevertheless, who can resist photographing the Western tiger swallowtail as it stops to nectar on a butterfly bush?
Lo and behold...
- Author: Kathy Keatley Garvey
Question: What's better than seeing a monarch butterfly?
Answer: Seeing two monarch butterflies sharing the same blossom on a butterfly bush!
Scenario: Monarchs (Danaus plexippus) from the Pacific Northwest are fluttering through Vacaville, Calif. and stopping in our pollinator garden for some flight fuel before heading off to their overwintering sites along coastal California.
Background: I am watching for tagged butterflies from the migratory monarch project of Washington State University entomologist David James. (After all, one tagged by his citizen scientist Steven Johnson of Ashland, Ore., on Aug. 28, 2016, fluttered into our yard seven days later. James said it flew 285 miles in 7 days or about 40.7 miles per day.)
Menu: In our pollinator garden, the flight fuel includes nectar from the Mexican sunflower (Tithonia rotundifola), tropical milkweed (Asclepias curassavica), butterfly bush (Buddleia davidii), and Zinnias, a genus of plants of the tribe Heliantheae within the family Asteraceae.
Action: On Sept. 27, a male monarch touches down on our butterfly bush and begins sipping nectar. Soon, another joins him.
The two monarchs engage in what appears to be a territorial battle. It's a kaleidoscope of orange and black wings, tumbling, wobbling, recovering.
And then, wings up! The monarchs take flight.
- Author: Kathy Keatley Garvey
Never be late for dinner or it might be all gone.
Take the case of the Mexican sunflowers, Tithonia rotundifola, that we planted last April for the monarchs. Monarchs seem to favor Tithonia more than any other nectar source in our pollinator garden. Second choice: the butterfly bush, Buddleia davidii.
May, June, July, and August came and went. The invited (and expected) guests were a "no show." Didn't they make reservations? Or did they forget?
The Tithonia drew honey bees, long-horned bees, syrphid flies, a praying mantis, and assorted butterflies. No monarchs.
In September, entomologist David James of Washington State University, who studies migratory monarchs, announced the monarchs are on their way from the Pacific Northwest to their overwintering sites along coastal California. "They're coming," he said.
Finally, on Sept. 16, a single monarch glided in, sipped some nectar on the Buddleia for a few seconds and left. Another monarch stopped by on Sept. 26, nectared on the Tithonia for a couple of seconds and vanished.
Where are all the dinner guests?
Finally, at 4:30 p.m. on Oct. 3, a male monarch arrived for dinner. And what a 12-course dinner it was on the Tithonia's remaining 12 flowers. He paused once to sample nectar from the Buddleia, but he obviously preferred the Tithonia.
Frankly, it's not been a good year for monarchs in our pollinator garden. Monarchs totally ignored the milkweed, their host plant, and almost disregarded the nectar sources. In comparison, back in 2016, monarchs laid about 300 eggs on our milkweed. In the migratory season, it was not uncommon to see seven monarchs in our garden at one time.
If any more monarchs arrive, they'll not get much Tithonia or Buddleia to fuel their flight to the overwintering sites. They'll have to settle for what's left of the nectar sources: African blue basil, catmint, lion's tail, Mexican petunia, and honeysuckle.
We're just glad one dinner guest showed up, although he was almost too late for dinner.
- Author: Kathy Keatley Garvey
Have are you faring during the COVID-19 crisis?
If you have a pollinator garden--or access to you--and a camera, you can step out of The Great Indoors and enjoy The Great Outdoors.
A newly eclosed Western Tiger Swallowtail, Papilio rutulus, however, can take your breath away.
This one recently visited our butterfly bush, Buddleia davidii, in our pollinator garden. It fluttered across the garden and headed straight toward one bush: the aptly named butterfly bush.
Wikipedia tells us: "The genus is found in four continents. Over 60 species are native through the New World from the southern United States south to Chile, while many other species are found in the Old World, in Africa, and parts of Asia, but all are absent as natives from Europe and Australasia. The species are divided into three groups based on their floral type: those in the New World are mostly dioecious (occasionally hermaphrodite or trioecious), while those in the Old World are exclusively hermaphrodite with perfect flowers."
There's a movement afoot NOT to plant Buddleia davidii (see the North American Butterfly Association's "The Great Butterfly Bush Debate"), but we've had ours for a decade, we keep it under control, and we love it for its beauty, its aroma, and its ability to draw a wide variety of insects.
Insects love it, too.
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 mastergardeners@countyofnapa.org or leave a phone message at 707-253-4143 and a Master Gardener will respond shortly.
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