The arrival of fall brings shorter days, cooler nights and a gradual winding down of garden activity. Flowers start to fade, while leaves turn glorious colors and begin to fall from the trees. For many gardeners, though, fall isn't a time to relax and put their feet up. That's because common garden advice tells us to rake up all those leaves, remove every dried stalk and maybe even begin a burn pile for branches and twigs pruned at this time of year.
Allowing the leaves to break down over the fall and winter months is a form of natural composting that adds back nutrients, increases soil tilth and feeds organisms necessary for healthy plants. In the prolonged drought we are experiencing, a layer of leaves helps to retain moisture and prevent blowing dust. Invertebrates that help control garden pests, provide food for birds and other wildlife, and pollinate plants depend on leafy ground for shelter and survival over the fall and winter months.
One way to gradually allow more leaves to do this useful work is to remove them only from lawns or walkways and pile them beneath the canopy of ornamental trees, shrubs and perennials (but away from trunks and stems) or on top of vegetable beds, using them as you would any layer of compost. Larger leaves may need to be crunched down or shredded to stay in place. And a light layer of soil can aid in holding leaves in place on windy days.
In addition to letting leaves compost naturally, there is another reason to do less clean up in our fall gardens. A very important group of invertebrates that benefit from and depend upon these garden “leftovers” are our native bees. Most people think immediately of bumblebees and honeybees when the subject of bees comes up. But in fact, California is home to 1600 species of native bees of various sizes, shapes, and colors, and all of them are important pollinators of flowering plants, shrubs and trees. Some are even considered essential crop pollinators for orchards and commercially-grown produce like alfalfa and tomatoes.
We are able to benefit in myriad ways from the huge diversity and beauty of flowering plants and the bounty of vegetables because of pollinators, especially bees. Bees and flowers evolved together, with flowers producing pollen and nectar needed for food at various life stages by all bees (they are vegetarians, whereas their wasp cousins are carnivorous). Bees help move pollen from one flowering plant to another, thus ensuring the plants' successful reproduction.
When we allow some leaves to break down naturally and keep some dried stalks and stems in our fall gardens, we are helping to provide nesting sites and shelter for native bees so they can survive the winter and emerge in spring to start a new generation.
Almost all native bees are solitary; after mating the female does the work of building and provisioning a nest and then lays her eggs. There are no queens or worker bees and most do not tend to the young, leaving them to complete their development into a new adult bee on their own. The majority of native bees have fairly brief life spans as active adult bees, often only living a few weeks or months.
Bumblebees, however, are social. They form nests with a queen and worker bees but unlike honeybees (which are not native to North America, and were introduced in the 1600s) the nest only survives one year with a newly mated queen flying off in the fall and finding someplace, often in the ground, to overwinter before emerging in spring to start a new nest. Leaving some leaves and garden litter helps the queen remain hidden and protected through the long winter months.
Different native bee species emerge throughout the spring, summer and fall, often appearing when the flowers they depend on are blooming. Our native manzanitas, California lilac and Western redbud, along with annuals and perennials like clarkia and California poppies, all bloom in early spring and are good examples of this seasonality. The associated bee visitors emerge from their winter nests and show up in our gardens around the same time these natives are blooming. Planting an abundance of flowering plants, mostly native, that bloom through the seasons is the best way to ensure the success of all pollinators.
About 70% of our native bees are ground-nesters. The remaining 30% nest in fresh or dried stems and wood, existing tunnels made by boring beetles or insects, rock cavities, or (in the case of bumblebees) old rodent holes or even man-made items like birdhouses. All their nests are in what can be called a linear space or tunnel and do not look like honeybee hives. Some species of stem-nesting bees use stems that are hollow (like reeds); others favor stalks that have soft interiors that they can chew through.
A good example of a stem nester that depends on dried stems or stalks is Ceratina, the small carpenter bee. She uses these pithy stems to build her nest, lay her eggs and overwinter as an adult bee. Flowering perennials that have long, fairly strong stalks with a softer or pithy interior are Ceratina's choice for nesting.
Leaving dried stalks in place (at a height from 8 to 24 inches) instead of removing them provides opportunities for these nests. Come spring, the new bees emerge and the female, after mating with a male bee, starts chewing from the top of the stalk (or sometimes through its side) to form a tunnel. She gathers a pollen and nectar ball and provisions this tunnel, laying her egg on top of the food source. She then seals this into a cell and builds another. Usually, five to six cells are formed in each tunnel. Ceratina is a bit unusual as she doesn't close the top of the nest and will guard it from predators. The next generation develops into adults and spends the winter inside the nest tunnel, emerging in spring to start the cycle again. You can watch these cut stems for any activity!
The past year's stubble with old nests will quickly decompose through spring and new perennial growth will hide much of it. Additionally, letting dried seed heads remain often provides benefits to birds and other wildlife that eat the seeds. When and where feasible, leaving stumps of trees or piles of brush in place can also provide nesting sites for tunnel nesters, bumblebees, and other winter hibernators.
Ground-nesting bees need areas of bare soil or ground that is lightly mulched or covered with a thin layer of leaves. They tunnel down to build their nests, complete with chambers and cells, provisioning them and laying their eggs. They too need these nest sites to survive winter. Not tilling the soil if possible and avoiding pesticides helps them nest successfully. Pesticides are problematic in many ways for invertebrates; ground-nesting bees have added risk as they use their mouths to excavate the soil, putting them in contact with any pesticides present in the dirt near their nests.
Ground-nesting bees can use just about any texture of soil that will hold together. A garden area that has stepping stones with soil between them is a great potential nest site for these bees, with the advantage of providing protection to the nest. Scientists with the Xerces Society for Invertebrate Conservation (a national non-profit organization) have observed that ground-nesting bees often nest at the edge between lawn and garden. This may be because bees, especially the smaller species, often don't fly far from their nests to forage, so the proximity of their nest to flowers, their food source, is beneficial.
Most of our native bees will go about their business with no regard to us. They are a fascinating and often beautiful group of insects, mostly unwilling or even unable to sting. They tend to live harmlessly and unnoticed, unless we take the time and effort to look for them.
Making some or all of these small, but potentially significant, changes to our gardening habits (and aesthetics) each fall has the potential to encourage the population growth of these important insects while, at the same time, increasing the health of the soil in our gardens. Tell your friends and neighbors that you're “leaving some leaves,” and stems, for the benefit of healthier plants and for the sustenance of wildlife, including our very important pollinators -- native bees.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
As concern grows over the decline in the honey bee population, alternative pollinators are gaining attention. Mason bees, which are native to North America, are one option. These gentle-natured bees do not produce honey but they excel at pollinating and are easy to raise.
The mason bee is a solitary bee which lives in natural cavities such as woodpecker holes or hollow stems. They also seem to be just as happy in artificially-constructed nests, so long as these nests include tubes made of cardboard or paper where the female bee can lay her eggs.
Purpose-built nests, often called bee boxes, are set out in early spring when daytime temperatures regularly reach 55 degrees. The bee box is placed outside, facing south in a location that is sunny but protected from wind and rain. Because mason bees will not fly farther than three hundred yards from their nest, bee boxes must be located within range of fruit trees and flowering plants.
The mason bee gathers pollen on her underside. As she zig-zags among the blossoms she is picking up and dropping off pollen, thus pollinating the flowers as she travels. One mason bee can pollinate 2,000 blossoms in a single day. She brings pollen back to her nest and deposits it at the back of the tube, making a mound on which she will lay one egg. She then seals the space off with mud to create a cell. It is because they use mud in their nest construction that they are called mason bees.
All this activity can be closely watched since the bees don't sting. The female can be seen heading into her chamber when she is laden with pollen, and backing into her chamber when she is about to lay an egg. Sometimes she just likes to rest in the front of the chamber. This activity continues for six to eight weeks, and then the mother bee dies.
Mason bee larvae hatch a few days after their eggs are laid. The larvae eat the pollen the mother has provided and then each larva goes into a pupal stage. The following spring, the adult bees emerge. The males emerge from the nest first, the females follow, and the process begins all over again.
More information on mason bees can be found at the Crown Bees website.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
It's important to protect our bee populations because their survival and reproduction provides pollination benefits for agricultural, urban, and wildland environments. This is especially evident here when we welcome commercial bees to pollinate almond orchards each spring. These almond blossoms are only the beginning of the rich agricultural smorgasbord relying on pollination from bees. Our bubble of bee knowledge is largely limited to social bees that live in colonies and are used commercially in orchards, fields, and green houses. The most well-known in the American landscape, the honeybee (Apis mellifera L.), was first introduced by European settlers along the Eastern seaboard in the early 17th century. Documentary evidence tells us it took over 200 years for the European honeybee to make its way to California.
While there are over 4,000 species of bees found in North America, California is home to 1,600 native species. These natives were here prior to the arrival of European honeybees. European honeybees may have been introduced to California in 1853 from swarms purchased in Panama, carried across the Isthmus, and shipped to San Francisco. Apparently only one swarm made the arduous trip and was delivered to F. G. Appleton, a San Jose apiarist. Until this time, diverse native bee communities were the primary pollinators, filling a wide range of ecological roles throughout our state.
Native bees are actually better adapted to meet the needs of a broad diversity of flowering plants in urban, suburban, and rural areas. While one third of our food crops rely on both native bees and commercial honeybees for pollination, home gardens mostly rely on healthy native bee populations. It's been estimated that only 25 to 40 percent of native flowering plant species are pollinated by honeybees. In order to protect ecosystem resilience and diversity, we need to protect the health of our native bees.
Most native bees are not aggressive and are not inclined to sting since unlike honeybees they are not protecting their hive. Males generally have no sting. Females may sting if swatted or stepped on, but they don't have enough venom for the sting to be painful. Native bees range in size from tiny to large and vary in color.
Some of the natives seen in my Paradise garden include the following:
- Carpenter bees (Xylocopa varipuncta) are social, forming a small colony that nests in wood. The female Valley carpenter bee is about an inch long black bee that resembles a bumble bee but is less hairy. The male, commonly known as "the teddy bear bee," is green-eyed and blond. Small carpenter bees (Ceratina) also tunnel into wood, are nearly hairless, and are metallic-looking. Some species sport yellow markings and can be mistaken for flies.
- Sweat bees (Halictidae)are attracted to salty sweat. This species of bee is metallic green, blue, or black with greenish-yellow markings.
- Bumble bees (Bombus). Feral honeybees and bumble bees constitute a large percentage of the bees I see daily. Like honeybees, bumble bees are social and live in small colonies, unlike the solitary native bees.
Native bees are unsung heroes. Some, such as the yellow-faced bumble bee (Bombus vosnesenskii) are better pollinators than honeybees because of their foraging behaviors and large, hairy bodies. Agricultural crop systems, as well as urban and wildland environments, benefit from native bees. The reproduction and survival of diverse species of native bees depend on all of us. Dr. Gordon Frankie, professor and research entomologist at University of California, Berkeley, recommends the following to protect our native bee populations:
- Eliminate pesticides
- Plant a diversity of nectar and pollen rich plants (ten or more species)
- Mass each plant in patches of ten square feet
- Choose plants that bloom in succession over the growing season
- Avoid excessive pruning and manicuring of ornamental flowers
- Set aside bare patches of soil for nesting
Not only will these behaviors help protect our bee populations, but they will also attract other pollinators.
Many factors contribute to declining native bee numbers: increased use of chemicals; loss of wildflower meadows and other suitable habitats; more land being developed for commercial and residential property, landscapes incorporating more hardscape and fewer pollen-producing plants. Plus, homeowners are quick to call pest control companies to eradicate unwanted bugs rather than try to implement Integrated Pest Management (IPM) methods. The solution to turning around the declining health of native bees is to act individually and proactively, as well as to raise awareness. Here are some steps we can take:
- Support local nurseries that sell plants and seeds that haven't been treated with neonicotinoids, a class of pesticides commonly used as seed treatments (NSTs) and systemic sprays in greenhouses.
- Buy organic vegetable seeds or packs.
- Ask if in doubt about a particular plant you're interested in purchasing. The same applies to food. Supporting local farmers markets helps promote sustainable agriculture, and may help keep harmful pesticides out of the soil and water. Many of the venders at farmers markets do not use neonicotinoids when growing their fruits, flowers, and vegetables. And they are right there at the market to talk about their farming practices.
Learning to manage your pests through IPM tactics will also help minimize adverse effects on declining bee populations. The University of California's IPM website provides scientific, location-specific pest control information for homeowners. Homes become less toxic to pets and children when their play areas are not treated with pesticides. Homeowners can share what's working in their gardens with neighbors and friends, which may help eliminate pesticides in other yards and gardens.
Providing food, shelter, and nesting areas for wildlife in the garden will also help our native bees. Pollen is protein for bees and nectar is their carbohydrate, providing energy and maintaining water balance in their diet. Plant a variety of annuals and perennials in the garden for bees to enjoy. Provide water sources. A shallow dish filled with pebbles and water will not only provide bees with a drinking station but will help other beneficial insects as well.
It is vital that our bee populations are protected. Their survival and reproduction provide pollination benefits that sustain our planet. While native bees go unnoticed, learning more about them and protecting their natural habitats will help assist these prolific pollinators and insure our own well-being.
To learn more about bees, investigate the following sources:
- The Xerces Society
- The UCANR publication, Native Bees are a Rich Resource in Urban California Gardens
- The Pollinator Partnership
- The UC Berkeley Urban Bee Lab
- Real Dirt article by Cindy Weiner, “Bumble Bees in the Garden
Information in this article has been derived from:
- California Native Plant Society, Small Wonders: The Plight and Promise of California's Native Bees by Emily Underwood, June 24, 2021Ecosphere, volume 11 issue 2 February 2020
- Ecosphere, volume 11 issue 2 February 2020, Dara A. Stanley, Simangele M. Msweli, Steven D. Johnson, Native honeybees as flower visitors and pollinators in wild plant communities in a biodiversity hotspot
- Kellar, Brenda, Honey Bees Across America
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu (preferred) or call (530) 538-7201.
One of the amusements a garden can provide is watching the birds, bees, butterflies and other critters drawn to it. Most of us have seen honeybees flying from flower to flower, sipping nectar or collecting pollen to take back to their colony. Honeybees, however, are not native to the western hemisphere. They originated in Eurasia and Africa and were imported to North America by immigrants in the 17th century. Before that time, pollination services for both wild and cultivated plants were provided by a host of native bees. There are about 4000 different species of bees native to the United States, and 1600 of those species are found in California. Most of these bees are solitary with each female making her own nest; most often the nests are in the ground, but some bee species nest above ground.
Bumble bees are one group of native bees. The body of a bumble bee generally has lots of black hair with contrasting bands of yellow, red, or white. Different species have different color patterns. Bumble bees are as large as or larger than honeybees. Female honeybee and bumble bee workers both have pollen baskets on their hind legs, which they use to carry the pollen they collect. A pollen basket is a shallow depression in the leg surrounded by a fringe of long hairs. Workers and males are similar in size, but queens are much larger. Both queens and workers have stingers, but they are not aggressive and rarely sting. Males don't have stingers.
When the workers become adults, they take over foraging for nectar and pollen. The queen remains in the nest to lay more eggs as the colony grows and develops.
In late summer,some of the fertilized eggs are fed more frequently and longer than usual. These develop into new queens. The queen also lays some unfertilized eggs that will develop into male bees. Once they leave the colony, the males forage to feed themselves but don't return to the nest. They spend their days eating and searching for new queens to fertilize. At night they sleep in trees or shrubbery. In the fall the old queen, workers and males all die. Each new queen hibernates separately in a cavity in the ground until it is time for her to emerge the following year to begin her own colony.
As a bumble bee moves around inside the flower, pollen collects on her hair; she uses her legs to transfer the pollen to the pollen basket. Some flowers have pollen that is contained within tubular anthers that open only at one end or through a narrow slit on the side. These anthers must be vibrated or shaken to release the pollen through the opening. Plants that function in this way include some common garden vegetables like tomatoes, eggplants, potatoes and peppers, as well as native plants like shooting stars and manzanita. Bumble bees (along with a few other bee species, but not honeybees) have evolved a specialized method called buzz pollination to obtain pollen from these plants. Bumble bees grasp the tubular anthers while vibrating their flight muscles without moving their wings. The vibration shakes the pollen loose, and it falls onto the bumble bee. Having bumble bees in your garden can increase the yield of these crops.
Some insects superficially resemble bumblebees, but if you look closely, you can tell the difference. Carpenter bees have bodies that are mostly black and shiny with far less hair than bumble bees. The Valley Carpenter Bee is enormous, about one inch long, much larger than a bumble bee. The females are shiny black, and the males are fuzzy golden yellow with green eyes. Syrphid flies have abdomens that are striped black and yellow, but flies have only two wings and antennae that are short and stubby. Clearwing sphinx moths are yellow and black but larger than bumble bees. They hover in front of a flower, rather than landing on it, and their antennae are long and feathery.
Upcoming opportunity to learn more about bumble bees: John Whittlesey, owner of Canyon Creek Nursery and Design, will be presenting “Living with Bumble Bees” online on Wednesday, April 7 at 7pm during the general meeting of the Mount Lassen Chapter of the California Native Plant Society. This meeting is free and open to the public. Go to the chapter website and click on the program title to access the link to the Zoom meeting.
The Master Gardeners Spring Workshop Series has begun. Topics include: Diagnosing Plant Problems; Mason Bees; and Native Gardens. Others will be added soon. Visit our workshop webpage to read about these upcoming free workshops and to register (required).
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu (preferred) or call (530) 538-7201.
By Tom Hansen and Jeanne Lawrence, Butte County Master Gardeners, January 4, 2013
Honey bees will be brought to Northern California from all across the US to begin pollinating the almond crop by mid-February. Although almonds don’t have a lot of nectar, they do have a lot of pollen, which allows the bees to build up the strength of their colonies after the arduous journey of travelling across the country.
Honey bees can forage as far away as three to five miles from their colony when conditions are favorable for flight, although most foragers tend to stay within a few hundred yards of the colony if it is near adequate food rewards (nectar and pollen). Honey bees will venture out from their hives when temperatures reach the mid-50s Fahrenheit; they won’t travel far, but they will search for sources of pollen and nectar nearby.
Because honey bee queens are constantly laying eggs and raising their young, these bees need food year-round. Honey bees forage when temperatures are 55 degrees and higher; they do not forage in rain or in wind stronger than 12 miles per hour. Cloudiness also reduces flight activity, especially near threshold temperatures. A honey bee normally flies at a speed of 18 miles per hour empty and 15 miles per hour carrying of load of pollen or nectar. However, if they are agitated and empty, honey bees can fly about 20 miles per hour. They cannot carry a load upwind against much more than a 15 mile-per-hour wind.
Native bees, like bumble bees and mason bees, are solitary and do not live together in hives like honeybees do. Solitary native bees were here long before the arrival of honey bees, which were introduced from Europe in the early 17th century. Native bees lay their eggs throughout the summer and fall and their pupae (young) develop in seclusion during the colder months. They need daytime temperatures of 65 to 70 degrees before they emerge as adults, so they will not begin pollinating until early April, or when daytime temperatures rise. While native bees do not play a significant role in almond pollination, they are critical in pollinating many of our summer fruits, vegetables and flowers.
Different species of pollinators are attracted to different types of flowers (generally those that suit their tongue length), but nearly all types of bees show interest in blue, yellow and ultraviolet hues.
Some guidelines for bee-friendly garden plantings include the following:
- Natural species (rather than hybrids) produce nectar and pollen that is more accessible for bees
- Native flowers can attract solitary bees (like mason bees)
- Grow a variety of species from different plant families
- Try to have something flowering throughout the season
- Plant several of one type of plant together – they will provide a better magnet for the bees
You can help bees out by planting mustards or clover as a cover crop – yellow mustard is one of the earliest blooming flowers that are attractive to honey bees. Native plants and shrubs that are attractive to bees include the California wildflower “Baby Blue Eyes,” and California Desert Bluebells, both of which are annuals; and California Dutchman’s Pipe, an attractive deciduous vine festooned with cream-colored flowers that have red-purple veins.
Non-native plants that are bee-friendly in our area include flowering quince, which is often the first noticeable flowering shrub of the year; the popular evergreen camellia japonica, some varieties of which bloom as early as November; and witch hazel (hamamelis), a yellow-flowering shrub with a distinctive fragrance and intriguing blossoms.
Crocus and hyacinth bulbs are also attractive to bees. These should be planted in November or December after spending 10 weeks chilling in a refrigerator ahead of time (as our climate is too mild to provide them the requisite chill hours) – and, like tulips, these are best treated as annuals in our climate.
When doing your winter garden clean-up, keep the bees in mind: leave some “wild,” messy areas in your yard for bees. For example, old fence posts, dead logs, and decaying sunflower heads all provide native bees with places to hide, nest, and raise their next generation.
Keep other pollinators in mind, too: for instance, instead of using a hummingbird feeder which you might only sporadically keep filled, provide natural nectar at this time of year by planting camellias, flowering quince and flowering currant.
Photo: Honeybee on prune blossom
