- Author: Kathy Keatley Garvey
An 11-member team of researchers led by UC Davis scientists reveals insight on "how and why" in a newly published article in the journal New Phytologist.
The title, "Flower Orientation Influences Floral Temperature, Pollinator Visits and Plant Fitness," tells part of the research, headed by senior author Stacey Harmer, professor of plant biology, College of Biological Sciences.
"Sunflowers face the rising sun because increased morning warmth attracts more bees and also helps the plants reproduce more efficiently, according to a study by researchers at the University of California, Davis," wrote UC Davis science writer and public information representative Andy Fell in a news release.
"While sunflowers are growing, their heads turn back and forth to track the sun during the day," Fell related. "Previous work from Harmer's lab showed that this tracking is controlled by the plant's internal circadian clock."
Some excerpts from the UC Davis news story:
"...as the flower heads, or capitula, mature and their stems become stiff and woody, this movement decreases until the heads are all facing the morning sun. When postdoctoral researcher Nicky Creux changed the orientation of sunflowers by turning their pots around, she (Harmer) noticed that east-facing flower heads attracted a lot more bees, especially in the morning, than plants facing west."
"The orientation of the plants also affected flower development and reproductive success. East-facing plants tended to produce larger and heavier seeds. They also released pollen earlier in the morning, coinciding with the times when bees visit."
The team included scientists from the Harmer lab, as well as researchers from the University of Virginia and UC Berkeley.
The researchers summarized their work--funded by the National Science Foundation and the U.S. Department of Agriculture's National Institute of Food and Agriculture (USDA-NIFA)--with these four key points:
- Effective insect pollination requires appropriate responses to internal and external environmental cues in both the plant and the pollinator. Helianthus annuus, a highly outcrossing species, is marked for its uniform eastward orientation of mature pseudanthia, or capitula. Here we investigate how this orientation affects floral microclimate and the consequent effects on plant and pollinator interactions and reproductive fitness.
- We artificially manipulated sunflower capitulum orientation and temperature in both field and controlled conditions and assessed flower physiology, pollinator visits, seed traits and siring success.
- East-facing capitula were found to have earlier style elongation, pollen presentation and pollinator visits compared with capitula manipulated to face west. East-facing capitula also sired more offspring than west-facing capitula and under some conditions produced heavier and better-filled seeds. Local ambient temperature change on the capitulum was found to be a key factor regulating the timing of style elongation, pollen emergence and pollinator visits.
- These results indicate that eastward capitulum orientation helps to control daily rhythms in floral temperature, with direct consequences on the timing of style elongation and pollen emergence, pollinator visitation, and plant fitness.
You can read the entire paper here.
Harmer and Creux created a video that illustrates the research, basically "that bees prefer to visit east-facing sunflowers than sunflowers that have been turned to face west. East-facing sunflowers are warmer and release pollen earlier to coincide with bee visits." Access the YouTube video below.
![A honey bee heading toward an east-facing sunflower in Vacaville, Calif. (Photo by Kathy Keatley Garvey) A honey bee heading toward an east-facing sunflower in Vacaville, Calif. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/85435.jpg)
By Julie Pramuk, UC Master Gardener of Napa County
At this time of year, you can spot sunflowers growing in many gardens and along roadsides in Napa Valley. Sunflower stems can grow nine feet tall, producing large. stunning flowers.
These cheerful plants have been cultivated in North America for centuries, used for food, medicine, dyes and oil. By 1500, the Spanish conquistadors had exported them to the rest of the world.
Last February, when I was planting sunflower seeds in my small cold frame, my granddaughter asked if she could have some of the seeds to plant. I was delighted and told her that it would be best to start the seeds in a bright inside spot so she could see them germinate, then plant them in her sunny back yard and keep them watered.
We both transplanted our seedlings in April. Mine, although healthy, were much slower growing. I noticed that the summer sun doesn't reach my garden until about 10 a.m. I also observed that, as my sunflowers grew, the heads all faced east as if waiting for the sun to come over the hill behind our garden. Then, as the sun progressed across the sky, the sunflower heads followed the path of the sun. As I watched my sunflowers each day, I wondered why and how this flower followed the sun.
Its Latin name, Helianthus, is rooted in two Greek words: helios, meaning sun, and anthos, meaning flower. In Italian, the word for sunflower is girasole, meaning to go around the sun.
In Greek mythology, the sunflower's origin is rooted in a love story. Apollo, also known as Helios, the sun god, was admired and loved by many, including a beautiful water nymph named Clytie. Every day she would follow his path across the sky from east to west.
Sadly, Apollo never returned her affection for he was in love with Daphne, daughter of a water god. Unfortunately for Apollo, Daphne did not love him. Clytie never gave up in her love for Apollo. So she became a sunflower following the path of the sun from the moment it rises in the east until it sets in the west.
Although this is a charming story of unrequited love, there is a reason why the sunflower turns its head toward the sun. Scientists say these young plants exhibit a trait known as heliotropism, or tracking the path of the sun. The phenomenon can be explained by circadian rhythms, the behavioral changes tied to an internal clock that we humans share, which follows a roughly 24-hour cycle.
The sunflower faces east at dawn and greets the sun, then slowly turns west as the sun moves across the sky. During the night the flower slowly turns back east to repeat the cycle.
Stacey Harmer, a professor of plant biology at UC Davis, told Science magazine that this behavior was a prime example of a plant's clock modulating its growth in a way that benefits the plant.
Researchers have found that the plant's turning is a result of different sides of the stem elongating at different times of the day. Growth rates on the east side of the plant are high during the day and low at night, whereas growth rates on the west side are low during the day and higher at night. Once a sunflower is mature, the circadian clock ensures that the plant reacts more strongly to early morning light than the afternoon or evening light as it gradually stops moving westward.
Research also reveals that east-facing flowers attract five times as many pollinators because the flowers heat up faster. Bees like warm flowers. Just like people, plants rely on daily rhythms to function.
Because of the sunflower's ability to attract pollinators, the sunflower was chosen for an experiment to see how the earth's pollinators are doing. The Great Sunflower Project is a fun, interactive family project that you can access online. Join other citizen scientists in helping scientists to evaluate and improve the habitat for pollinators. When you learn that one-third of our food depends on pollinators, you realize how important they are.
The sunflower is remarkable for its history, variety of flower heads, easy cultivation and vigorous bloom from early summer through fall as well as for its important role in attracting pollinators. Like Clytie, you may find yourself falling in unconditional love with this spectacular plant.
Food Growing Forum: Join Napa County Master Gardeners on Sunday, September 27, from 3 p.m. to 4 p.m., for a free Zoom forum on “Harvesting and Storing Produce.” This forum on food growing will continue monthly on the last Sunday of every month. To receive the Zoom link for the September 27 forum, register at http://ucanr.edu/FoodGrowingForum2020.
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.
![Sunflower 1 (yoel-j-gonzalez-unsplash) Sunflower 1 (yoel-j-gonzalez-unsplash)](/blogs/blogcore/blogfiles/73695.jpg)
![Sunflower 2 (thomas-despeyroux-unsplash) Sunflower 2 (thomas-despeyroux-unsplash)](/blogs/blogcore/blogfiles/73696.jpg)
![Sunflower 3 (audrius-sutkus-unsplash) Sunflower 3 (audrius-sutkus-unsplash)](/blogs/blogcore/blogfiles/73697.jpg)
By Susanne von Rosenberg, UC Master Gardener of Napa County
Sunflowers are one of those flowers that just seem designed to bring us joy. Who can avoid smiling when we see their bright, cheery faces?
There are many other things to love about sunflowers as well. They are a great food source for bees and other pollinators. Birds, squirrels and humans appreciate the seeds. You can eat sunflower seeds raw or roasted, and you can grow tasty sunflower seed sprouts for your salads and sandwiches. If you grow taller sunflowers, they can also make a nice screen during the summer.
Annual sunflowers (Helianthus annuus) are easy to grow. You can grow them in the ground or in containers. If you plant the seeds directly in the garden, you may need to protect the seedlings from hungry critters. Cover seedlings with floating row cover or fine mesh wire cages until they are six inches high or so; humans are not the only ones who appreciate juicy sunflower seed sprouts.
You can also grow seedlings and then plant them out when they're around six inches tall, or when their stems and leaves have toughened up. To grow well, sunflowers need full sun.They grow best in fertile, well-drained soil with a lot of mulch and regular watering. Tall varieties, especially, need good soil and plenty of water.
Sunflowers come in a huge variety colors and sizes. Colors range from creamy white to dark maroon. Depending on the variety you choose, the blossoms can be less than two inches across or the size of dinner plates. They also come with primarily single or branched stems.
If you're growing sunflowers for cut flowers, look at the description to make sure that they will have stems long enough for the types of bouquets you have in mind. Shorter varieties (less than four feet tall) are better for container gardens. You can grow taller varieties in containers, but they may need support.
Many varieties grow more than six feet tall. The tallest varieties I have seen in seed catalogs are said to reach 16 feet. While yours may not grow quite that tall, they would still be very tall sunflowers. The Guinness Book of World Records says that the tallest sunflower on record was grown in 2014 and was just over 30 feet tall.
What we think of as a single sunflower is actually a large inflorescence. This means the flower head is composed of many tiny flowers called florets. Central florets look like the center of a normal flower while the outer florets look like yellow petals and together they make up a "false flower."
This design helps insects and birds to easily see the sunflower. Every little floret that is pollinated produces a seed. Sunflowers were first domesticated in the Americas, and were part of many traditional native “Three Sisters” garden designs.
You may have heard that sunflowers follow the sun. That's true for young sunflowers. At dawn the head of the flower faces east and moves west throughout the day. When sunflowers reach full maturity they no longer follow the sun and continuously face east.This eastward orientation allows the sunflower to warm up quickly in the morning and thus get more pollinator visits.
Sunflowers produce a flower within three months of germination, and seeds typically ripen 30 to 45 days later. If you want to harvest some seeds, don't wait until the flower starts to dry or the birds will likely harvest them for you.
You'll need to cover the flowers from which you want to harvest seeds before the seeds mature. (Leave some flowers uncovered for the birds.) You can look for seeds forming inside the flower head and check the underside of the flower. The underside will turn from green to yellow and then brown as the flower matures. Cover the flowers with a material that permits air circulation (such as floating row cover, fine netting or cheesecloth) as they start to turn from green to yellow and tie the covering shut several inches below the flower.
Another recommended method is to simply cut the flowers when the back turns from green to deeply yellow and then put the seed heads in a dry, warm location to cure. Harvest sunflower seeds by cutting flower heads 4 to 12 inches down the stalk. (Cut below any covering to keep the mature seeds that have already fallen out of the flower head.)
If you have the room, you can grow a sunflower “house” for your kids or grandkids. Simply plant a double row of tall sunflowers in a circle that is large enough for the kids to sit in comfortably. Remember to leave an opening for them to get into their “house.” You've just created a great shady private space for them to enjoy all summer long. You can share the joy that sunflowers bring by growing some where neighbors can see them as they pass.
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.
![Sunflowers, (bonnie-kittle-unsplash) Sunflowers, (bonnie-kittle-unsplash)](/blogs/blogcore/blogfiles/69681.jpg)
![Bees love sunflowers (UC Davis) Bees love sunflowers (UC Davis)](/blogs/blogcore/blogfiles/69684.jpg)
![Sunflower seeds are food for many (Colourbox) Sunflower seeds are food for many (Colourbox)](/blogs/blogcore/blogfiles/69683.jpg)
![Colors of sunflowers (Victoria Advocate) Colors of sunflowers (Victoria Advocate)](/blogs/blogcore/blogfiles/69690.jpg)
![Really tall sunflowers (Etsy) Really tall sunflowers (Etsy)](/blogs/blogcore/blogfiles/69686.jpg)
![Shorter sunflowers (stella-de-smit-unsplash) Shorter sunflowers (stella-de-smit-unsplash)](/blogs/blogcore/blogfiles/69680.jpg)
![Close up of sunflower inflorescence (PxHere) Close up of sunflower inflorescence (PxHere)](/blogs/blogcore/blogfiles/69691.jpg)
![Sunflowers follow the sun when young (aaron-burden-unsplash) Sunflowers follow the sun when young (aaron-burden-unsplash)](/blogs/blogcore/blogfiles/69682.jpg)
![Protected sunflower head (Farm and Dairy) Protected sunflower head (Farm and Dairy)](/blogs/blogcore/blogfiles/69692.jpg)
![Sunflower to enjoy (rachael-henning-unsplash) Sunflower to enjoy (rachael-henning-unsplash)](/blogs/blogcore/blogfiles/69678.jpg)
![(ceeces-travel-unsplash) (ceeces-travel-unsplash)](/blogs/blogcore/blogfiles/69679.jpg)
![Sunflower house (Two Men and a Little Farm) Sunflower house (Two Men and a Little Farm)](/blogs/blogcore/blogfiles/69689.jpg)
By Penny Pawl, U. C. Master Gardener of Napa County
Winter is a perfect time to start planning the pollinator garden you will create in the spring. Start by deciding just where you would like to put the garden. Some people have taken out the center of their lawn and created a space for a garden for pollinators.
Pollinators are extremely important to the global ecosystem. Without them, many people would starve because food plants would not get pollinated. You can help by making an area in your garden hospitable to them.
Last fall, I picked out an area in my garden and decided to line it with hardware cloth because gophers had started to pull down my precious milkweeds. I dug up those milkweeds, then a helper laid wire over the soil and used building blocks to hold the wire in place. Over the winter, my helper added various soils and compost to create an area where the plants would grow. Soil was added to the openings in the building blocks.
Meanwhile, I was researching the plants that bees, birds and butterflies love. These plants have to be full of nectar as some pollinators need nectar for daily food and others need it to store in their nests.
I especially wanted to add nectars that would attract bumblebees. I have always had bumblebees in summer, but for some unknown reason, they disappeared the previous July. This year, I found the queen feeding on purple salvia in October. The queen is much bigger than the workers and usually stays in the nest while the workers gather nectar.
My next step was to start buying seeds of the plants I wanted. As soon as the weather warmed a bit, I started the seedlings in my hothouse. I had learned that marigolds, zinnias and salvias were pollinator favorites. For me, there is nothing more enjoyable than settling down on a long winter night with a stack of seed catalogs. Our bees, butterflies and birds evolved with California native plants, so that's what I chose.
Once you determine where you want your pollinator garden you can start to prepare the area for planting. Add a mixture of compost and soil. Let these two elements mix over winter, giving ground worms and small insects a chance to start working. Ground worms sift the soil through their gut and make tunnels for water to move through.
I found that bumblebees especially love ‘Hot Lips' salvia from Mexico. They drill a hole in the back of the flower to get directly to the nectar. Honeybees also visit my garden because there are hives nearby and some of them nap for the night in the flowers.
Native bees are small and often nest in the ground or in holes in trees and other wood. They visit my garden often for nectar.
Monarch butterflies need native milkweed to raise new generations so I grow two or three different native milkweeds in my pollinator bed. Some milkweeds come back from the roots, so you plant once and they continue to produce.
Sunflowers are always a good choice. I experimented with a Mexican sunflower with small flowers using seeds I bought online. Birds and squirrels are especially fond of sunflowers so plant a variety. I added more flowering plants to the mix, and as the flowers formed seeds, I plucked them and saved the seed.
Before I planted anything, I had a one gallon-per-hour drip line laid in the bed. Once plants got established, I watered once a week. Native plants don't require a lot of water, so that schedule was sufficient. For fertilizer, I used sifted worm compost which has all the trace elements plants need.
Above all, make your pollinator garden your own creation, with plants that you love and that they will, too. The pollinators will be grateful.
Next workshop: “Citrus: Preserve It, Serve It” on Thursday, January 16, from 1 p.m. to 4 p.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Presented by UC Master Food Preservers. For more details and online registration call 707-253-4221 or visit http://napamg.ucanr.edu.
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.
![Consult CNPS for natives to plant in your garden (CNPS Consult CNPS for natives to plant in your garden (CNPS](/blogs/blogcore/blogfiles/64729.jpg)
- Author: Pamela Kan-Rice
Enjoying a tasty sunflower seed snack? Cooking with sunflower oil? Thank a California sunflower seed grower for producing the hybrid seed that's used for planting sunflower crops throughout the United States and the world, for confectionery and oil seed production.
California farmers grow about 70,000 acres of sunflower, mostly in the Sacramento Valley, for hybrid seed stock.
“We have perfect conditions for growing sunflowers, with hot, dry summers and plenty of good irrigation water for producing high quality seed,” says Rachael Long, UC Cooperative Extension farm advisor in Yolo, Solano and Sacramento counties. “We also have good pollination by honey bees and field isolation from wild sunflowers, needed for high yields and genetic purity of planting seed stock.”
Indeed, take a look at the lovely fields of sunflowers blooming in the summertime. Their striking show of bright yellow faces across the valley's vast agricultural landscapes elicit feelings of warmth and happiness.
“But don't stop there!” says Long. “Take a closer look at the fields and you'll see rows of plants with single large flowers alternating with rows of smaller plants with multiple flowers. Stalks with single flowers are female, smaller ones are male; cross pollination occurs by honey bees to produce the hybrid planting seed, harvested from the single female flowers.”
To assist farmers in producing hybrid sunflower seed crops, Long led a team of researchers to produce a new 2019 sunflower hybrid seed production manual for California. The manual provides information on production needs, such as irrigation and nutrient management, as well as a color guide to insect pests, diseases, and weeds of concern for hybrid sunflower seed production.
“In order to ship seed to worldwide markets, strict field certifications are in place to ensure that pests endemic to California are not spread elsewhere,” Long says. Weeds, insects and diseases growers should watch for are identified in the manual.
“Sunflower Hybrid Seed Production in California” is available for free download at https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8638. In addition to Long, authors of the manual include UC Cooperative Extension farm advisors Sarah Light and Konrad Mathesius, retired USDA plant pathologist Thomas Gulya, UC Cooperative Extension irrigation specialist Khaled Bali, and emeritus UC Cooperative Extension soils specialist Roland Meyer.
“A special thanks to the sunflower seed industry and associate editor Dan Putnam, UC ANR agronomist at UC Davis, for their extensive contributions to this manual to make it a valuable resource for sunflower seed growers,” Long adds. “All of us are also grateful to UC ANR Communication Services for putting together a high quality publication!”