- Author: Ann Edahl
What do pollinators do?
Pollinators pollinate flowers by moving pollen from the anther (male part of a flower) to the stigma (female part of the flower), either on the same flower or a different flower. The pollinators are there to collect nectar or pollen from the flower for food. While they browse they disperse the pollen grains among the flowers, allowing the plant to reproduce.
Stone fruit, almonds, apples, squash, watermelon, and many other fruits and vegetables rely on bees for pollination. And pollinators can help self-pollinating vegetables such as tomatoes. Native bees pollinate a variety of native and non-native plants.
What can we do to help?
- Edging your vegetable bed with flowering annuals is both pleasing and beneficial. They look lovely and attract pollinators to your vegetables. (Allow your herbs to flower, rather than pinching back for increased production, to make them attractive to pollinators.)
-
Create a dedicated pollinator garden. You might focus on a garden that attracts butterflies, or one that attracts native bees.
-
While mulching provides many benefits, try to include areas of bare soil. This creates a more hospitable habitat for our ground-dwelling bees.
-
Think about replacing an ornamental plant or even a section of your lawn with plants that attract pollinators.
-
Plan for succession of blooms to provide food for the pollinators throughout the growing season. Annuals such as zinnias can be particularly useful because of their long bloom time.
Selection of pollinator magnets for Fresno County
Consider including some of the following plants in your landscape. This list is by no means exhaustive, but they have all worked in Fresno-area gardens.
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California native annuals, perennials and trees that are easy to incorporate into the urban garden include California poppy (Eschscholzia californica), hummingbird sage (Salvia spathacea), Cleveland sage (Salvia clevelandii), yarrow (Achillea spp. – there are both native and non-native yarrow), California lilac (Ceanothus ‘Ray Hartman' does particularly well in the garden), desert willow (Chilopsis linearis), manzanita (Arctostaphylos spp. which come in all sorts of sizes), and Western redbud (Cercis occidentalis)
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Perennial herbs, such as thyme (Thymus ssp.), oregano (Origanum vulgare), lavender (Lavandula spp.), rosemary (Rosmarinus officinalis), winter savory (Satureja montana), dill (Anethum graveolens, an annual that reseeds), rue (Ruta graveolens), and scented geranium (Pelargonium) make a great addition, planted throughout the landscape or in a dedicated herb garden,
-
Perennials: sages (Salvia spp.), lantana (Lantana camara), and butterfly bush (Buddleia davidii) are just three of many non-native perennials that attract a variety of pollinators.
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Annuals: try easy-to-grow marigold, zinnia (Zinnia) and sweet alyssum (Lobularia maritima),
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Trees: Japanese maple (Acer palmatum) is a bee magnet in the spring.
Read more:
Ponder, Frankie, Elkins, et al. 2013. How to Attract and Maintain Pollinators in Your Garden. ANR Publication 8498. University of California Agriculture & Natural Resources.
University of California Davis Arboretum and Public Gardens. 2018. Support Native Bees with These 10 Plants.
- Author: Denise Godbout-Avant
Pollinators receive food in the form of nectar (source of sugar) or pollen (source of protein, fat, and other nutrients). In the process of moving from flower to flower to feed, pollinators disperse pollen grains among plants of the same species, enabling the plants to reproduce. Flowers have evolved over long periods of time into many colors, shapes and scents to attract their pollinators, thus creating a mutually beneficial relationship.
The Pollinators
While bees are the primary pollinators, other insects including butterflies, moths, flies, beetles, wasps, some birds such as hummingbirds, and bats also play important roles.
Honeybees & Native Bees
Honeybees (genus Apis) are the bees we are most familiar with. However, honeybees are just one species of a very diverse group with over 20,000 species worldwide, 4,000 species in the USA and 1,600 in California. Native bees come in a variety of shapes, colors, sizes and lifestyles that make them very efficient pollinators. Unlike honeybees and bumblebees, which are social bees living in colonies, native bees are solitary with 70 percent nesting in the ground with the rest nesting in wood and plant stems.
Butterflies
Butterflies are daytime flying insects who often have gorgeous colorful wings. Their larvae sometimes require a specific plant to feed on, though most adults will get their nectar from many plants.
Moths
Moths are mostly evening and nighttime fliers, though some are out in the late afternoon or early morning. They are attracted to sweet-smelling flowers. Less colorful than butterflies, they are easily differentiated from butterflies by their “feathery” antennae.
Flies
Flies are not generally thought of as pollinators, however many are, particularly hover flies (family Syrphidae) and bee flies (family Bombyliidae), both of which are generalist pollinators. Generalist pollinators visit a wide range of plants, making them important inhabitants of gardens and fields.
Beetles
Beetles are a large group, with up to 28,000 species in the USA. Most beetles are not pollinators, but some do visit flowers for nectar or pollen and help fertilize some flowering plants, particularly magnolias.
Wasps
Hummingbirds
Hummingbirds are the most prominent pollinating birds in the Americas. With their long beaks, they can reach deep into flowers while sipping nectar. In addition to nectar, they also forage on insects and spiders.
Bats
Bats are nocturnal pollinators that play an important role in pollinating cacti and agave, as well as many tropical and subtropical plants including bananas, avocados, century plants and cashews. Species such as Mexican long-nose bat (Leptonycteris nivalis) have evolved heads and long tongues to access light-colored flowers which open at night, often producing abundant nectar and pollen.
How You Can Help Pollinators
Pollinators need a diversity of flowers with lots of nectar and pollen. They require easy access to flowers blooming throughout the seasons, particularly during late winter, early spring, and late autumn seasons when fewer flowers bloom. Different flower species provide differing amounts of nectar. Native plants generally provide more nutritious nectar for pollinators, so they attract more pollinators. Download the Xerces Society Recommended Plants for the Central Valley Region for a list of plants.
To help protect pollinators, if you choose to use a pesticide, select one that are less toxic, such as an insecticidal soap or oil. Avoid broad-spectrum sprays that kill numerous insects. Spray on non-windy days in the early morning or late evening when pollinators are not present. Use UC Integrated Pest Management for information on pests and pest management (https://ipm.ucanr.edu/).
Citations
- The Pollinator Partnership https://www.pollinator.org/
- Xerces Society book: Attracting Native Pollinators: https://xerces.org/publications/books/attracting-native-pollinators
- California Native Plant Society (CNPS) native planting guides: https://www.cnps.org/gardening/choosing-your-plants/native-planting-guides
Free Resources from University of California and your local UC Master Gardeners
- CA Friendly Friendly Garden Recipes https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8518
- How to Attract and Maintain Pollinators in your Garden https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8498
- UC Stanislaus County Master Gardener: Butterflies in Your Garden with list of plants that attract butterflies: https://ucanr.edu/sites/CEStanislausCo/files/345791.pdf
- Gardening for Pollinators and Diversity from UC Davis Arboretum: https://arboretum.ucdavis.edu/pollinator-gardening
- Bees in the Neighborhood: best practices for urban gardeners. https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8596
Books and ID Cards for Purchase
Common Plants to Attract California Native Bees https://anrcatalog.ucanr.edu/Details.aspx?itemNo=3557
Want both cards? Bundle and save $10 at https://anrcatalog.ucanr.edu/Details.aspx?itemNo=3557BUN
Denise Godbout-Avant has been a UC Cooperative Extension Master Garden in Stanislaus County since 2020.
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- Author: Ryan Hill
- Author: Marcelo Moretti
Introduction:
Pollinator insects are essential to produce many economically and nutritionally important crops grown in the western USA. These crops include blueberries, almonds, sunflowers, cucurbits, and many others. Almond pollination in California plays a vital role in the apiary industry, driving beekeepers to haul huge numbers of bee colonies to California for the few weeks in late winter when almonds bloom. Bees are selective of the pollen and nectar they forage, and diverse floral resources can allow bees to forage according to their nutritional needs (Leponiemi et al. 2023). Planting pollinator habitat in natural areas, gardens, and agricultural land is one method of supporting bee health. Irrigated agricultural land in the western USA can be an excellent resource for bees during the dry summer when flowers are rarer. However, the resident weeds in these settings are often not of high nutritional quality for hungry pollinators. To make matters worse, pollinator habitat in agricultural fields can be choked out by competition from weeds. Our control plots from these studies (Figure 1) demonstrate that point effectively.
Figure 1: Control plots at all three experimental sites were extremely weedy. This sometimes meant that none of the planted species could grow, as seen in the pictures above.
Objective:
The studies described here attempt to use herbicides to improve the chances for success in pollinator habitat establishment.
Methods:
Three locations in Oregon's Willamette Valley were selected for studies. Two were hazelnut orchards watered with drip irrigation, and one was a field plot set up for sprinkler irrigation. Each location received different soil preparation. The first orchard location (Corvallis) was not tilled, and soil compaction issues were present. The second orchard location (Amity) was power-harrowed, so the top two inches of soil were loosened. The third location (Lewis-Brown Research Farm) was plowed and disked.
All three locations were seeded in the fall with a set of flowering species with potential for pollinator habitat (Table 1).
Table 1: Species and seeding rates used for pollinator habitat establishment in Oregon's Willamette Valley. |
||
Common Name |
Scientific name |
Lb/Acre |
Hairy vetch |
Vicia villosa |
60 |
Lacy Phacelia |
Phacelia tanacetifolia |
12 |
California poppy |
Eschscholzia californica |
8 |
Farewell to spring |
Clarkia amoena |
2 |
Globe Gilia |
Gilia capitata |
2 |
Sweet alyssum |
Lubularia maritima |
2 |
These species were planted in rows, and herbicide treatments were applied over the top perpendicular to planting rows (Table 2). Four herbicides were applied post-emergence, and the rest were applied one day after planting (pre-emergence). Glyphosate treatments were only included in the orchard trials. Experimental plots were set up as a randomized complete block design with four replicates, and each species was treated as a separate experiment. A crop oil concentrate at 1% v/v was included for Motiff (mesotrione) and Basagran (bentazon), while a nonionic surfactant at 0.25% was included for Matrix (rimsulfuron) and Quinstar 4L (quinclorac). All post-emergent treatments (and glyphosate) included ammonium sulfate (AMsol 1% v/v).
Table 2: Trade name, active ingredient, and rate of herbicides applied to pollinator habitat species. Pre-emergent herbicides were applied at planting, and post-emergent herbicides were applied 30 days after crop emergence. |
||
Trade name |
Active Ingredient |
Rate (product/A) |
Pre-emergent treatments |
|
|
Cornerstone Plus |
Glyphosate |
3 qt |
Alion |
Indaziflam |
4 fl oz |
Trellis SC |
Isoxaben |
21 fl oz |
Devrinol 2XT |
Napropamide |
8 qt |
Chateau SW |
Flumioxazin |
6 oz |
Prowl H2O |
Pendimethalin |
6.3 pt |
Princep |
Simazine |
4 qt |
Motiff |
Mesotrione |
6 fl oz |
Post-emergent treatments |
||
Motiff |
Mesotrione |
6 fl oz |
Matrix |
Rimsulfuron |
4 oz |
Quinstar |
Quinclorac |
12.6 fl oz |
Basagran |
Bentazon |
2 pt |
In Amity, competition from perennial grasses resulted in poor stand establishment. A grass-selective herbicide (clethodim) was used, and the site was reseeded six months after the initial planting when soil conditions were appropriate.
Results and discussion:
Site differences.
Drastic differences were seen between sites. Table 3 shows how crop coverage differed between the three sites for each species.
Coverage at the Corvallis site was deficient for all species except hairy vetch.
Several species did very well at the Amity location. Phacelia in the glyphosate plots was exceptionally well established due to glyphosate's good control of perennial grasses that were not killed by the power harrow.
Lewis-Brown (LB) plots had the best crop establishment initially. However, this location had intense pressure from perennial weeds, so the initial crop establishment did not translate to superior pollinator habitat. The plots at LB where Alion was applied produced a good stand of Canada thistle (Cirsium arvense) by the end of the trial, which the bees loved.
Table 3: Crop Coverage for each species at each location is shown here. The values reported are from the treated plots with the highest coverage. |
|||||||
% Crop coverage (Best treatment) |
Site |
Vetch |
Phacelia |
Poppy |
Gilia |
Clarkia |
Lobularia |
Plowed and Disked |
Lewis-Brown Research Farm (LB) |
100 |
100 |
75 |
84 |
97 |
98 |
Power harrow |
Amity |
55 |
81 |
47 |
47 |
34 |
47 |
No tillage |
Corvallis |
89 |
11 |
28 |
0 |
15 |
0 |
Pre-emergent treatments
Pre-emergent herbicides often had inconsistent pollinator species safety; however, several combinations seemed safe. Napropamide was safe for Phacelia, Gilia, Clarkia, and Lobularia, while flumioxazin and pendimethalin were safe for poppy (Table 5). All five species only had adequate crop establishment at two of the three locations. Hairy vetch establishment was improved by simazine applications at all three locations, but crop coverage was not significantly different from the untreated control for this species (Table 5). Figure 2 shows the treatment by species combinations that were sometimes safe versus the combinations that were consistently safe for the planted species.
At the two orchard sites, glyphosate treatments were the best for Gilia, Phacelia, and poppy establishment (Table 5).
All three trials were conducted on fine soils with organic matter content ranging from 2-7% (USDA-NCSS soil survey). The safety of pre-emergent herbicides for pollinator species establishment may vary depending on soil characteristics.
Post-emergent treatments
Post-emergent (POST) applications were challenging to evaluate for safety. Weed control efficacy was inadequate, and so often, crop establishment was not good enough to confidently assess crop injury.
One exception was hairy vetch. This species exhibited good tolerance to a post-emergent application of Basagran, a result seen at all three locations. The results from two trials suggest that Clarkia tolerated POST applications of Quinstar. Not enough data were collected to conclude the other four species. See Table 4 for crop coverage data.
Conclusions
Site preparation was an essential consideration in our study. Soil compaction and perennial weed pressure must be addressed to have a successful pollinator habitat planting. It was also clear that pre-emergent herbicides can improve habitat establishment, but safety must be adequately established. This is especially true of different soil types and environments. In California's Central Valley, pendimethalin has been seen to occasionally cause injury in poppy plantings, which is in contrast with this study.
Table 4: Spring crop coverage (%) from plots treated with post-emergent herbicides one month after planting, which happened the prior October. Missing data from Phacelia and Lobularia at LB is due to crop loss from frost injury. |
|||||||
Crop coverage (%) |
|||||||
|
Corvallis |
Amity |
LB |
|
Corvallis |
Amity |
LB |
Hairy Vetch |
|
|
|
Gilia |
|
|
|
Untreated |
29 |
28 |
98 b |
Untreated |
0 |
8 |
54 b |
Mesotrione |
21 |
3 a |
0 a |
Mesotrione |
0 |
0 |
0 a |
Rimsulfuron |
18 |
1 a |
0 a |
Rimsulfuron |
0 |
4 |
78 b |
Quinclorac |
34 |
0 a |
28 a |
Quinclorac |
0 |
0 |
6 a |
Bentazon |
50 |
26 b |
94 b |
Bentazon |
0 |
7 |
47 b |
Phacelia |
|
|
|
Clarkia |
|
|
|
Untreated |
0 |
53 ab |
|
Untreated |
3 a |
0 |
83 b |
Mesotrione |
0 |
42 ab |
|
Mesotrione |
0 a |
0 |
34 b |
Rimsulfuron |
5 |
17 a |
|
Rimsulfuron |
4 ab |
0 |
55 b |
Quinclorac |
5 |
64 b |
|
Quinclorac |
15 b |
0 |
77 b |
Bentazon |
2 |
48 ab |
|
Bentazon |
6 ab |
0 |
0 a |
Poppy |
|
|
|
Lobularia |
|
|
|
Untreated |
2 |
11 |
2 |
Untreated |
0 |
0 |
|
Mesotrione |
3 |
11 |
0 |
Mesotrione |
0 |
0 |
|
Rimsulfuron |
6 |
0 |
0 |
Rimsulfuron |
0 |
0 |
|
Quinclorac |
2 |
5 |
3 |
Quinclorac |
0 |
0 |
|
Bentazon |
2 |
9 |
0 |
Bentazon |
0 |
0 |
|
Table 5: Spring crop coverage for pre-emergent herbicide treatments applied just after planting, which happened the prior October. Phacelia and Lobularia experienced winter kill at the LB location, so reported data is coverage from December for that location. |
||||||||
Crop coverage (%) |
||||||||
|
Corvallis |
Amity |
LB |
|
Corvallis |
Amity | LB | |
Hairy Vetch |
|
|
|
Gilia |
|
|
|
|
Nontreated |
29 |
28 ad |
98 b |
Nontreated |
0 |
8 a |
54 c |
|
Glyphosate |
23 |
46 bd |
|
Glyphosate |
0 |
47 b |
|
|
Indaziflam |
6 |
3 d |
79 b |
Indaziflam |
0 |
3 a |
36 bc |
|
Isoxaben |
11 |
17 ab |
83 b |
Isoxaben |
0 |
5 a |
31 ac |
|
Napropamide |
8 |
19 ab |
91 b |
Napropamide |
0 |
38 b |
56 c |
|
Flumioxazin |
5 |
36 bd |
90 b |
Flumioxazin |
0 |
18 a |
2 c |
|
Pendimethalin |
6 |
38 bd |
98 b |
Pendimethalin |
0 |
0 a |
13 ab |
|
Simazine |
34 |
55 d |
98 b |
Simazine |
0 |
44 b |
6 ab |
|
Mesotrione |
6 |
25 abc |
0 a |
Mesotrione |
0 |
3 a |
8 ab |
|
Phacelia |
|
|
|
Clarkia |
|
|
|
|
Nontreated |
0 a |
53 bc |
96 b |
Nontreated |
3 |
0 a |
83 b |
|
Glyphosate |
11 b |
92 c |
|
Glyphosate |
5 |
34 b |
|
|
Indaziflam |
0 a |
13 ab |
90 b |
Indaziflam |
0 |
0 a |
74 b |
|
Isoxaben |
0 a |
0 a |
82 b |
Isoxaben |
0 |
8 a |
88 b |
|
Napropamide |
2 a |
81 c |
98 b |
Napropamide |
0 |
25 b |
86 b |
|
Flumioxazin |
0 a |
30 ab |
57 ab |
Flumioxazin |
0 |
5 a |
20 a |
|
Pendimethalin |
0 a |
0 a |
15 a |
Pendimethalin |
0 |
2 a |
67 b |
|
Simazine |
0 a |
75 c |
56 ab |
Simazine |
0 |
30 b |
0 a |
|
Mesotrione |
2 a |
54 bc |
99 b |
Mesotrione |
0 | 0 a | 25 a | |
Poppy |
|
|
|
Lobularia |
|
|
|
|
Nontreated |
2 a |
11 |
2 a |
Nontreated |
0 |
0 a |
70 c |
|
Glyphosate |
30 b |
42 |
|
Glyphosate |
0 |
21 ab |
|
|
Indaziflam |
2 a |
8 |
8 a |
Indaziflam |
0 |
0 a |
16 ab |
|
Isoxaben |
2 a |
3 |
69 b |
Isoxaben |
0 |
0 a |
0 a |
|
Napropamide |
6 a |
14 |
0 a |
Napropamide |
0 |
47 c |
98 d |
|
Flumioxazin |
2 a |
31 |
63 bc |
Flumioxazin |
0 |
15 a |
34 b |
|
Pendimethalin |
2 a |
40 |
64 b |
Pendimethalin |
0 |
0 a |
0 a |
|
Simazine |
0 a |
46 |
28 ac |
Simazine |
0 |
44 bc |
5 a |
|
Mesotrione |
0 a |
7 |
8 a |
Mesotrione |
0 | 3 a | 3 a |
Figure 2: Crop coverage pictures from two months after planting the Lewis-Brown research farm show that the planted species (rows) tolerated several pre-emergent herbicides (columns). A black outline surrounds successful combinations seen in at least one of the other two trials. Combinations that were never seen to be successful again are surrounded by a red outline.
References:
Leponiemi, M., Freitak, D., Moreno-Torres, M. et al. (2023). Honeybees' foraging choices for nectar and pollen revealed by DNA metabarcoding. Sci Rep 13, 14753. https://doi.org/10.1038/s41598-023-42102-4
Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at the following link: http://websoilsurvey.sc.egov.usda.gov/.
- Author: Alison Collin
Amsonia, a plant native to the Northeastern USA, seems to be little known in the West. They are commonly known as bluestars on account of the shape and color of their flowers. I have never found it in local nurseries, but I have always been curious to find out how it would do in the Eastern Sierra since it is said to be hardy in USDA zones 3-11.
They like well draining soil and regular water, but are somewhat drought tolerant once established. They need partial shade in the hottest areas. Rabbits and deer tend to avoid eating it unless forage is scarce.
There are several different species of Amsonia, but Amsonia hubrichtii is considered to be one of the best bluestars which has needle like but soft foliage, sky-blue flowers and a bright gold autumn foliage color.
I planted an Amsonia hybrid “Blue Ice” about three years ago in a pollinator garden with sandy soil which I amended by the addition of a little compost, and it has performed very well. It makes a neat clump of foliage about 2 feet tall, with sturdy green stems which are black near the tips. The star-shaped, sky-blue flowers erupt in mid-April. The foliage has good fall color, after which the stems die down completely for the winter. It is not at all invasive, and the single clump has gradually increased in size.
They are relatives of Nerium oleander, and they contain a milky sap which can irritate skin. They are said to be hosts to swallowtail butterfly caterpillars.
One day recently, when the plant was in full flower, I was stunned to witness a frenzy of carpenter bees working the flowers! There were at least 23 bees — some massive — on the clump at the same time, together with 3 bumble bees, two other species of native bees that I could not identify, two different butterflies, and a ladybug! I have never seen a plant with so much pollinator activity at one time. Interestingly, these bees are all natives to our area, although the plant is not, and I have never seen a domestic bee on it.
I am pleased that I tried it.
Further information can be found at:
https://www.chicagobotanic.org/sites/default/files/pdf/plantinfo/fg187_amsonia.pdf
- Author: Lisa Nedlan
I can name that flying insect in 3 clues – how about you?
Match the clue to the insect's image. Place an X in the appropriate column.
Resources:
UC IPM, Syrphids (Flower Flies or Hover Flies) https://ipm.ucanr.edu/natural-enemies/syrphids/
University of Florida, European honey bee https://entnemdept.ufl.edu/creatures/misc/BEES/euro_honey_bee.htm
University of Minnesota Extension, Syrphid flies https://extension.umn.edu/beneficial-insects/syrphid-flies
US Forest Service, Syrphid fly (Sphaerophoria philanthus) https://www.fs.usda.gov/wildflowers/pollinators/pollinator-of-the-month/syrphid-fly.shtml
Utah State University Extension, Beneficial Predators: Syrphid Flies https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=2969&context=extension_curall
Photo credits:
Honeybee photo by Leo Kriss: https://www.pexels.com/photo/macro-photography-of-honeybee-perched-on-blue-petaled-flower-754313/
Syrphid Fly photo by Leslie Saunders on Unsplash