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Saturday, April 29, 2017

Valley Carpenter Bee – Xylocopa varipuncta

Female Valley Carpenter Bee (Xylocopa varipuncta) on California encelia
Mother Nature's Backyard Garden

We love the insects in Mother Nature’s Backyard. In fact, our gardens are specifically designed to attract many types of pollinators, from hummingbirds and bees to moths and flies. But each spring we particularly look forward to the large bees.  Just recently we saw one of our favorites, a female Valley Carpenter Bee (Xylocopa varipuncta).  We thought you might enjoy learning about this interesting native pollinator.  Its scientific name is pronounced: ZIE-low-co-puh  vair-ee-PUNK-tuh).

Valley Carpenter Bee is the largest native bee in California. It belongs to the genus Xylocopa (the Carpenter Bees), a genus with approximately 500 species world-wide.  In general, the Carpenter Bees are large, wood-nesting bees found in a variety of habitats, from the sub-tropics to temperate woodlands. 
Female Valley Carpenter Bee (Xylocopa varipuncta) -
busy in spring
The Valley Carpenter Bee is native to Southwestern U.S. from California to Texas and south into Northern Baja California, Mexico.   Its common name honors California’s Great Central Valley, where this species does, indeed, occur.  But this bee flies throughout the California Floristic Province (W. of the Sierras) and is fairly common in S. California.   Xylocopa varipuncta lives where ever there is wood for nest-building.  In the wilds, this is most commonly in the lower elevation oak and riparian woodlands of California’s valleys and foothills.  But the species is also seen in urban gardens, particularly those with native plants.

The species Xylocopa varipuncta is the most sexually dimorphic of all the Xylocopa species.  You may have seen the males and females and believed them to be separate species.  Females are large (15-25 mm; ½ to 1 inch), shiny black bees.  They are relatively slow flyers, although they don’t spend long periods on individual flowers.  But if you wait patiently, you can get good pictures of this large bee.

Female Valley Carpenter Bee (Xylocopa varipuncta)
The female Xylocopa varipuncta looks like a large, black bumblebee with amber-colored wings.  The body color is black: black head, thorax, abdomen, legs and antennae.  The female body is shiny, but closer inspection shows that legs, thorax and posterior abdomen are actually quite hairy.  In fact, females can pick up quite a load of pollen, making them look superficially like a black and yellow bumblebee (see below).
Female Valley Carpenter Bee (Xylocopa varipuncta) on
 Arroyo Lupine.  Note yellow pollen.
Male Valley Carpenter Bees are smaller, very hairy and a striking golden brown color. They also have amazing pale green eyes - there is no other California bee like them.  They are sometimes called ‘Teddy Bear Bees’ because of their resemblance to the childhood toy.  In fact, the males can be aggressive to other bees, but are quite harmless to humans; only the females can sting (and then, usually only when you’re harassing them).

Male Valley Carpenter Bee (Xylocopa varipuncta)

Curious male Valley Carpenter Bee (Xylocopa varipuncta)

The males have been difficult for us to photograph.  They are shy creatures that are almost always in motion. We finally managed to photograph of one (above).  For more good photographs of both males and females, we recommend references 2, 3 and 4, below.

Like all of the Carpenter bees, Xylocopa varipuncta nests in cavities in wood. The females excavate the tunnels with their stout mandibles (jaws), usually choosing softer wood like willow or partly decomposing limbs, stumps or logs.  While not a ‘challenge’ species like the Eastern Carpenter Bees, in urban areas Xylocopa varipuncta sometimes nests in unpainted, untreated wood (like redwood posts).

It takes quite a strong bee to be able to chew through wood!   We recently drilled some ‘starter holes’ in a stump.  A female Carpenter bee has been eyeing them – perhaps she’ll stay?    There are so many places for cavity-dwelling bees to nest in a preserve like the Gardena Willows Wetland Preserve (where our gardens are located). 

Female Valley Carpenter Bee (Xylocopa varipuncta)
 checks potential nest site
Valley Carpenter bees overwinter as adults in these tunnels, emerging in the spring (our earliest photos in western Los Angeles County are from early January).  Then the females start to forage and the males start to cruise.  There is much work to be done in spring. First, mating must occur. And then the nesting cavities must be prepared and provisioned, all prior to egg laying.

Valley Carpenter Bees are adaptable.  If hollow-stemmed plants (like bamboo or Elderberry) are available, they create unbranched, linear nests in the stems.  If not, they create or enlarge branched nests in wood.  The branched nests usually contain 6-8 chambers; each will contain a single egg, as well as a supply of ‘bee bread’.  The ‘bee bread’ is a mixture of pollen and nectar made by the female.  It supplies food for the developing bee.

Like everything about Xylocopa varipuncta, their eggs are large (about ½ inch long or a little more; 12-15 mm).  The larvae develop in the nest, emerging as adults in late summer (usually August).   You can often see young adults nectaring in the summer and early fall garden.  The bees hibernate in the nest tunnels over winter, emerging again in the spring or late winter (as early as January in western Los Angeles County).

The mating behavior of Xylocopa varipuncta has been well-studied.  There are many fascinating aspects – more than we can discuss in this short posting.  We refer the interested reader to an excellent Wikipedia posting on the species [ref. 1].

As native plant gardeners, we encounter more insect species than do conventional gardeners.  This is a good thing; it in part explains why native plant gardens tend to be more productive and pest-free than other local gardens.  But, how do we evaluate – and explain to our neighbors – whether a particular insect is a pest or beneficial insect?   We suggest weighing the potential harms against the potential benefits.

The potential harms associated with the Valley Carpenter Bee are two: 1) nesting in wood structures; 2) stings.  Given the choice, Valley Carpenter Bees will choose to nest in dead limbs, trunks, stems and other natural sites, rather than in structural wood [5].  They particularly avoid painted or treated wood.  So, unless you have untreated pine, redwood or cedar, nesting is unlikely to be a problem with our western Carpenter Bees.  You might even want to provide a ‘bee house’ or pieces of logs as suitable alternative nesting places.   And as to the stings, the females are really pretty docile.  They’ll only sting to protect themselves; given the choice, they prefer to avoid you.

As to the services Valley Carpenter Bees provide?  We see at least three: 1) pollination; 2) recycling dead wood; 3) human enjoyment.  The second service is most important in natural settings. In Preserves, parks and other natural areas, cavity-builders help begin the process of breaking down old wood. This is an extremely important service – but not much observed in most gardens. 

Female Valley Carpenter Bee (Xylocopa varipuncta) pollinating
 Tansy phacelia (Phacelia tanacetifolia)
Valley Carpenter Bees are important and efficient pollinators.  They can regulate their body temperature [1], allowing them to fly in temperatures both cooler and warmer than other pollinators.  Their hairy bodies allow them to pick up plenty of pollen and transport it to other flowers. They are also capable of ‘buzz pollination’ – literally shaking pollen from the anthers by vibrating their flight muscles.

Studies have shown that Carpenter Bees are more effective pollinators than European Honeybees for such varied plants as Passion vine, cotton, tomatoes and melons.  So we should welcome them into our gardens, and provide them sources of nectar from early spring into fall.


Nectar is the primary source of food and water for adult Xylocopa varipuncta. Obtaining nectar is easy from many flowers.  But some good nectar sources (including Manzanitas, Penstemons and other tubular flowers) present a real challenge for large bees.  Nectar is located deep within the floral tube, accessible only to those small enough or possessing a long tongue. This ensures that only the right creatures – those who actually perform the service of pollination – can access the nectar.

Female Valley Carpenter Bee (Xylocopa varipuncta) -
'stealing' nectar from Manzanita
The Valley Carpenter gets around this problem by cutting a slit in the floral tube and ‘stealing’ the nectar, without picking up any pollen in the process (see photo above).  These bees even pierce nectar-less flowers, possibly obtaining water, minerals or other chemicals from the plant sap [6].   So yes, these guys can be (adorable) thieves!


And that brings us to the last benefit of Xylocopa varipuncta in the home garden; the enjoyment we get from watching these interesting creatures.  Carpenter bees are large enough for all to observe.  Even the very young and the octogenarian can enjoy their antics.  Many a future biologist has been enthralled by garden bees and other insects. 

In fact, there’s much still to be learned about these bee’s behaviors. That’s the wonderful thing about insects: they’re all around us, yet they remain surprisingly un-studied.  Perhaps you, your child or grandchild, sitting in your garden, will discover something important.  All you need is time, a pair of binoculars (or good eyesight) and a garden that provides for our native pollinators.  What a bargain!





We encourage your comments below.   If you have questions about Duskywing butterflies or other gardening topics you can e-mail us at :  mothernaturesbackyard10@gmail.com



Saturday, April 22, 2017

March for Science

Get out and enjoy Earth Day.  Think about all the ways science impacts and enriches your life.  Consider becoming a Citizen Scientist.  The earth is ours to enjoy, learn about and protect.

Tuesday, April 4, 2017

Plant of the Month (April) : Fendler’s meadow-rue – Thalictrum fendleri

Fendler's meadow-rue (Thalictrum fendleri): in Mother Nature's Garden of Health

We love the California spring, when local perennials complement the spring-blooming shrubs.  In fact, we wish more gardeners included herbaceous natives in their garden plans.  One of the more interesting, Fendler’s meadow-rue, is blooming right now in Mother Nature’s Garden of Health.  The scientific name for this species is pronounced thal-ICK-trum  FEND-ler-eye.

Fendler’s meadowrue is an herbaceous perennial in the family Ranunculaceae (the Buttercup family).  This family, which includes genera like Ranunculus, Delphinium, Clematis, Aquilegia, Anemone, Hellebore and Aconitum, contains mostly herbaceous perennials and annuals.  Many have lovely flowers and are well-known garden plants.  Many also produce chemicals toxic to humans and animals, some of which are used in small doses as medicinals.

The genus Thalictrum includes plants from temperate regions on every continent except Australia.  The Meadow-rues (also called Meadow rues or Meadowrues) usually grow in damp, shady places.  Species and cultivars are widely used in gardens, both for their leafy foliage and their interesting flowers. 

Four Thalictrum species are native to California; two (Thalictrum sparsiflorum and T. fendleri) are native to S. California.  Thalictrum sparsiflorum, the Sparse-flowered meadow-rue, is endemic the Sierras and the San Bernardino Mountains.  Thalictrum fendleri is more widespread, growing primarily in Yellow Pine, Red Fir, Lodgepole Pine and Subalpine Forests throughout the state.  

Fendler's meadow-rue (Thalictrum fendleri): young plant

The two varieties, Thalictrum fendleri var. fendleri and Thalictrum fendleri var. polycarpum, both grow in Los Angeles County.  T. fendleri var. fendleri can still be found in the San Gabriel Mountains, while var. polycarpum grows in both the San Gabriels and the Santa Monica Mountains.  You may have seen them on hikes, growing on shady slopes or along streams in riparian woodlands.  Variety fendleri, the more widespread variety, grows throughout the western U.S. from Montana and Wyoming to Texas and northern Mexico; var. polycarpum can also be found in Nevada, Oregon, Utah and Baja California, Mexico.

Some taxonomists argue that T. fendleri var. polycarpum is better considered a separate species (Thalictrum polycarpum) [1, 2].   The specimen in our Garden of Health would then be that species; and some nurseries sell the plant under this name.  Whichever is correct, T. fendleri var. polycarpum tends to grow in slightly sunnier, drier locations, in Mixed Evergreen Forest and Oak Woodland communities.[3]     This variety can further be distinguished by its lack of foliage hairs and pink female flowers (those of var. fendleri are greenish white).

Fendler's meadow-rue (Thalictrum fendleri): plant
Fendler’s meadow-rue is an herbaceous perennial, with foliage mostly growing in a mounded clump 1-2 feet (30-60 cm) tall and 1-3 feet wide.  The flowering stalks are taller – 4 or 5 feet (1 meter or more) and have sparse foliage. The entire plant dies back (to the ground) in the dry days of late summer and fall, emerging again with the winter rains.

Meadow-rue’s foliage is one of its strong points, at least from a gardener’s perspective.   The foliage is quite similar to that of its close cousin, the Western columbine (Aquilegia Formosa; see above).  The leaves are medium-green to blue-green and have long, slender petioles (leaf stems).  The leaves are several-times compound, with rounded, irregularly dissected, terminal leaflets (see below).  The foliage is reminiscent of Maidenhair fern (but larger) or a delicate rendering of the Columbine.

Fendler's meadow-rue (Thalictrum fendleri): foliage

Fendler's meadow-rue (Thalictrum fendleri): young foliage
The young foliage is utterly enchanting to observe.  The young leaves, which are a bright yellow-green, emerge in spring fully formed but compacted.  As the petioles lengthen, the leaves unfurl to their final size.  The petioles often have a red-purple tinge, adding to the foliage spectacle.  Preformed leaves are found in some plants growing in cold climates. This trait protects delicate leaves but allows plants to leaf out quickly, once the weather warms up.   We wonder whether pre-formed leaves developed as a similar adaptation in our mountain-growing Meadow-rues.

Fendler's meadow-rue (Thalictrum fendleri): male flowers

Fendler’s meadow-rue is usually dioecious, with male and female flowers on separate plants.  Plants with some bisexual flowers sometimes also occur in this species. The flowers of both sexes grow on tall (3-6 feet; 1-2 meters), slender flowering stalks above the foliage. The only way to tell the plants apart is when they’re flowering.

Male flowers are the showier (above).  Neither male nor female flowers have petals (they do have small, green-white sepals).  But the male flowers have cascading yellow or purple stamens with prominent anthers (producing the yellow pollen).   The resulting flower cluster is unique and attractive.  When most gardeners describe Thalictrum fendleri’s unusual flowers, they are thinking of the male flowers.

Fendler's meadow-rue (Thalictrum fendleri): female flowers
Female flowers (above) also grow in clusters of 10-20 along a flowering stalk.  The female flowers are simple affairs, with a single, immature (green) fruit beneath the styles (female sex organs). Each fruit contains a single seed – an unusual situation in the plant world.  In T. fendleri var. polycarpum, the styles are medium to bright pink; in var. fendleri, they are green-white. 

Given the dangling anthers and simple flowers, it’s not surprising to learn that Thalictrum fendleri is a wind pollinated species [4].  The Meadow-rues are an interesting genus, with some members being insect pollinated and others wind-pollinated.

Why might separate male and female flowers – and wind pollination – have developed from the more common bisexual, animal pollinated condition of the Angiosperms (flowering plants)?  Those are questions that plant biologists are just beginning to seriously tackle.  And it’s genera like Thalictrum that can shed light on the genetic and environmental factors associated with the development of sexual differentiation and wind pollination.  For more on this exciting story see references 5-7, below.

Fendler's meadow-rue (Thalictrum fendleri): with other
shade-loving perennials.  Mother Nature's Garden of Health.
Being a woodland species, Fendler’s meadow-rue prefers part-shade to quite shady conditions.  It does well with morning sun or in the dappled shade under trees.  It’s not particular about soil texture; we’ve grown it in very sandy as well as clay soils.  It has a wide range of acceptable soil pH (5.0-8.0) and is fine with organic mulches.  As a woodland/riparian woodland species, it can also be grown in soils with higher organic content than many of our local natives prefer.

Fendler’s meadow-rue is actually quite drought tolerant, but will remain green well into summer with occasional to near-regular water.  Dress with a modest amount of organic mulch and plants will remain happy and disease-free.  The only problem we’ve had in our Garden of Health is wind damage to the delicate flowering stalks.  If you live in a windy area, you might want to consider a protected part of the garden. 

Fendler's meadow-rue (Thalictrum fendleri):
with Heuchera and native strawberries
Introduced into the horticultural trade by Theodore Payne [8], Fendler’s meadow-rue adds woodland charm to any shady garden.  It works well with the native ferns and other shade-adapted perennials like Western columbine, Solanum xanti, Douglas’ iris, wild strawberries and the Heucheras.  It’s often used under oaks, Blue elderberry and other trees. Other gardeners use it in moist places like rain gardens or shady swales.


This species makes a number of interesting chemicals, some of which are toxic to humans and animals.  No part of the plant should be ingested.  Native Californians made an infusion of the leaves that was wiped on the forehead for headaches.  A poultice of the foliage was applied for sprains.  In all areas where this plant grows, people were aware of its toxicity, and used it only sparingly – and always externally.

Fendler's meadow-rue (Thalictrum fendleri):
home garden, Redondo Beach CA.

In summary, Thalictrum fendleri is an interesting plant in an interesting genus.  While it produces toxic chemicals, so do many plants routinely included in gardens, including Delphiniums, Angel’s trumpet, Azaleas, Coral trees, Autumn crocus, Flowering tobacco and Hydrangea. Used with respect, this plant adds seasonal charm to local gardens.  If you’ve got a shady spot, it might be just the plant you need.

Fendler's meadow-rue (Thalictrum fendleri): Rancho Santa Ana Botanic Garden, Claremont, CA.

For plant information sheets on other native plants see: http://nativeplantscsudh.blogspot.com/p/gallery-of-native-plants_17.html


  1. http://www.smmflowers.org/mobile/PDF-species/Thalictrum_polycarpum_UCLA_SantaMonicas.pdf
  2. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233501272
  3. http://www.calflora.org/cgi-bin/species_query.cgi?where-taxon=Thalictrum+fendleri+var.+polycarpum
  4. http://onlinelibrary.wiley.com/doi/10.1111/j.1442-1984.2004.00103.x/full
  5. http://www.botany.wisc.edu/waller/PDFs/Steven.Waller.2007.pdf
  6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701749/
  7. https://oup.silverchair-cdn.com/oup/backfile/Content_public/Journal/mbe/30/8/10.1093/molbev/mst101/3/mst101.pdf?Expires=1491660526&Signature=OjeXvZqCcW7H5Qz4NEKkckoTNDEYkz3Yw2iGHz9kMa0V4~6ng7oY-mGi-J4GsAgKhhy95vOBm4HI6My18vnbuGY78GR0PE6mUJjxo9fRBrIG7cPTy6tYS~tRUwk2d80FI2Hnp-yBe87DYBUJIVpOBsBB1u8dl0RWzX8FSAZjhB0Y0CEd5r4wBqpWn2cuJ1LGuki46zRAy~uvumZ1I9WiUaqhaF62cMqGWC8kGMpEXkLCm2iazH0Za41bxf2NBGqzDZilZPsDhFenysTIdR4cWzTbRiXu3E219D8nxIEVm8mxSrTVaX97enjeO-bDVByUoCJ~I1auoj8lPIp3Di36Cw__&Key-Pair-Id=APKAIUCZBIA4LVPAVW3Q
  8. http://www.theodorepayne.org/mediawiki/index.php?title=Thalictrum_fendleri_var._polycarpum


We welcome your comments (below).  You can also send your questions to: mothernaturesbackyard10@gmail.com