By: Susanne von Rosenberg, UC Master Gardener of Napa County
Most of us know quite a bit about honeybees, and even other native bees. This summer I noticed quite a few bumblebees in my yard, and I was curious to learn more about them.
Worldwide, there are only 250 species of bumblebees; 26 are native to California. For comparison, California has 1,600 native species of bees (the world total is 3,600).
Like many other bee species, some bumblebees are also under threat. They can be threatened by human activities including habitat fragmentation, pesticide use, disease transmission and loss of native flowers.In June 2019 the California Department of Fish and Wildlife proposed four native bumblebee species for protection under the Endangered Species Act. They are Crotch's bumblebee, Franklin's bumblebee, Suckley cuckoo bumblebee and Western bumblebee. (Cuckoo bumblebees are more or less what you would expect: They invade the nests of other bumblebees, kill the queen and use the workers to rear their young.)
Like honeybees, bumblebees form colonies headed by a queen, but the colonies are much smaller, typically in the range of 50 to 400 individuals. Honeybee hives hold about 50,000 bees. The colony is formed by a queen, who burrows into the ground in the fall to overwinter and emerges in the spring to find a suitable nest site.
Nest sites are also usually underground and often are old mouse or other rodent burrows. She then builds cells, supplies the nest with pollen, lays eggs (which will have been fertilized the previous fall) and incubates the eggs on the pollen. She'll continue to gather nectar and pollen until the first female workers are ready to go out and get more. Once the new workers are able to supply the colony, the queen no longer has any need to leave the nest.
Like honeybees, bumblebees are corbiculate, which means they have pollen baskets on their hind legs. The queen will continue to lay eggs, and there will be several generations of workers during one season. By the fall, most of the colony will have died.
Young queens emerge from the nest in early fall to mate, often more than once. Male bees spend their whole lives looking for a queen to mate with. They are often forcibly driven out of the nest and rarely return once they emerge. Instead, they sleep under leaves or whorls of flowers at night.
Bumblebees vary in appearance but are generally plump and densely furry (covered in bristles). They are larger, broader and rounder-bodied than honeybees. Many species have broad bands of color that can be used to help distinguish different species.
Bumblebees are active under conditions in which honeybees stay at home and can readily absorb heat from even weak sunshine. The thick pile created by their bristles acts as insulation to keep bumblebees warm in cold weather; species from cold climates have longer bristles (and thus thicker insulation) than those from warmer climates.
Bumblebees can fly in much colder weather than honeybees because they can raise their muscle temperature by shivering. The temperature of the flight muscles needs to be at least 86°F before the bumblebee can fly. At an air temperature of 55°F, it takes about five minutes of shivering for a bumblebee to be able to fly.
Bumblebees are important pollinators of wildflowers as well as fruit and vegetable crops. Bumblebees can be separated into three different classes by tongue length: short, medium and long. Collectively, they can pollinate a wide variety of flowers. A few of the short-tongued species “cheat” to feed on long-tube flowers. They bite a hole in the flowers near where the nectar is produced and harvest the nectar through the hole.
Bumblebees also have a unique behavior called sonication. They vibrate their wing muscles to shake pollen grains out of the anthers of flowers. They'll visit flowers that don't produce nectar, such as tomato plants, to collect the pollen. Possibly bumblebees got their name from the buzzing sound they make when sonicating. They used to be called “humble bees” because they hum; that term eventually gave way to bumblebee because of their somewhat bumbling flight path.
You can help preserve bumblebees and continue to enjoy their antics by providing suitable habitat and food. Like other ground-nesting bees, bumblebees need areas of bare soil. If you till your soil, you will destroy the nests of any ground-nesting bees that may be present.
Bumblebees, like other bees, also benefit from a wide variety of nectar and pollen sources, particularly native flowers. If there aren't any native plants in your neighborhood, plant a small patch to help attract bumblebees. Better to create large groups of similar plants than to scatter them; larger groups are easier for bees to find.
If you are interested in learning more about bumblebees, download the U.S. Forest Service publication Bumble Bees of the Western United States, which covers all 40 species of Western bumblebees.
Food Growing Forum: Last Sunday of the month through October. Register to get Zoom link at: http://ucanr.edu/foodgrowingforum2020
Sunday, October 25, 3 pm to 4 pm, “Planting Onions, Leeks and Other Alliums and What Else to Do Now”
Napa Library Talks: First Thursday of each month. Register to get Zoom link. http://ucanr.edu/wildlifehabitat2020
Pollinator Gardening, Sundays, 1 pm to 2 pm. Register to get Zoom link.
October 11 – Caring for Your Pollinator Garden http://ucanr.edu/2020pollinatorpart4care
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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.
By Penny Pawl, UC Master Gardener of Napa County
When you are planning your summer garden, remember the pollinators. Bees and other pollinators are in trouble in California and across the U.S. and need our help. They are nectar feeders so put in plenty of blooming plants for them.
Without pollinators we would lose many food crops. There are 1,000 species of California native bees. Twenty-six of these are bumblebees and most of the rest are solitary bees.
The pollinators native to our area have evolved with the native landscape so it's important to have some native plants in your garden. Pollinators include native bees and butterflies. Honeybees are not native to the United States but were introduced for their honey. However, other pollinators are just as effective. Let me introduce you to some of our native bees.
For several years, I have created nests for the native mason bees. These nests consist of pieces of wood with 3/8-inch holes drilled into them. The one they visit most is a piece of firewood. Mason bees have nested in it repeatedly. I know they were there because of the mud in each hole.
Last year I actually saw the bees leaving their nests and then returning. They are about to come out this spring to pollinate the fruit trees. They don't spend much time flying around before they start building new nests for their babies.
The mason bee creates its nest in long narrow tunnels within the wood. The bees do not make these tunnels; they find them and move in. So I drilled the holes for them. The bees pack the holes with pollen, lay an egg, pack in more pollen and lay another egg. They put three to five eggs per hole depending on the depth. When they are done laying, around the first of April, they seal the holes with mud. I know the nest is full when I see mud in every hole. The eggs hatch the following spring.
This year I did not move the nest to a sheltered location. It appears that woodpeckers have tried to drill out the nest. I will wait and see how much damage the birds have done by the end of March.
I have bumblebees in my garden every year. They especially love my ‘Hot Lips' salvia from Mexico. They spend all day gathering nectar and are gentle.
Bumblebees nest in the ground. You should always leave a cleared area in your garden for them; they will not nest in mulch. I often find their little mounds. When they are done digging, you cannot tell they were even there. They love one particular area of my garden that I always keep clear of mulch.
I also see a lot of carpenter bees, the big bees that drill for nectar in the back of the flower. They are gentle and you can observe what they are doing easily.
They can be destructive when they drill into untreated lumber. I had them in my hothouse one year. They had drilled all the way to the end of a 12-foot-long 4 x 2 board. I had to replace that wood and paint it with latex to keep them out. Putting steel wool in the holes will also stop them. They do need a place to lay their eggs, however.
The male carpenter bee is a big brown teddy bear. He has only one purpose: to pursue females. He does not sting. I had a visit from one a few years back and he hung around me for a while. Once their mating duty is done, they die.
Digger bees and squash bees both nest in the ground. Squash bees emerge to pollinate squash and gourds. They are only present when these plants are in bloom. Even so, I hand-pollinate my squash to make sure I get fruit.
Bumblebees are said to buzz tomatoes, which are self-pollinating. Just to be sure the flowers do pollinate, I shake the vines every morning when I do my walk-through.
To lure pollinators to your garden, plan to have a variety of plants blooming every month of the year.
Workshop: UC Master Gardeners of Napa County will hold a workshop on “Growing Tomatoes” on Saturday, April 6, from 9:30 a.m. to 11:30 a.m. at University of California Cooperative Extension, 1710 Soscol Avenue, Napa.
Join our experienced tomato growers for tips and tricks on cultivating perfect homegrown tomatoes. Learn the latest research on tomato cultivation and care, and discover new and heritage tomato varieties. You'll get all the information you need to grow delicious and beautiful tomatoes in your own large or small garden or in containers. Growing America's favorite garden fruit is not only fun and easy, but also the best way to acquire healthy food for you and your family. Online registration (credit card only); Mail-in/Walk-in registration (check only or drop off cash payment).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County (http:/napamg.ucanr.edu) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.