Sunday, March 27, 2016


Erythronium hendersonii

Erythronium is one of my favorite genera of wildflowers. This year, for some reason, they are blooming prolifically to the delight of bees and myself alike! Honeybees, bumblebees, and anthophorine bees (Anthophora or Habropoda) are visiting the flowers of Erythronium hendersonii, and surely other species, feverously. I expect this year to be one of the best for seed production, the primary mode of reproduction (as opposed to vegetative increase) for E. hendersonii and oregonum, two species which I've been fortunate enough to observe directly in habitat this year.

Erythronium hendersonii
A short introduction for those not introduced to this genus: There are around 20 to 31 species in all, many from the Western US, a few in the Eastern US, and a some in Eurasia. They are in the lily family (Liliaceae), and so related to FritillariaLilium, and Tulipa among others. These are mostly Spring ephemerals, though some of the alpine and subalpine species bloom in the Summer as the snow melts. They grow from bulbs (some say corms), with tunics that don't seem to cover the entire bulb, thus they are susceptible to drying out. Contractile roots pull the bulbs down deeply, perhaps to help them evade herbivores (voles, etc.) and to keep them from desiccation is Summer.

Erythronium hendersonii mottled leaf. E. oregonum is similarly mottled.
Many of the species have mottled or spotted leaves, some plain green. In general, mottled leaves are found in species growing in the West while spotted leaves are found in species in the East and Eurasia. Flowers are often born singly (sometimes in clusters in mature and happy plants, and nearly all species have flowers that face downwards (except Erythronium rostratum, a yellow-flowered American forest dweller of the central-southern states). Most are probably bee pollinated, though they aren't specialized and can probably be pollinated by a variety of insects, including flies.

Erythronium hendersonii, one anther dehisced
The pendant flowers have multiple beneficial consequences. First is to exclude inefficient pollinators, since pendant flowers are difficult for many insects to land on (beetles or butterflies, for example, struggle to land on fully pendant flowers). Bees are the primary pollinators of Erythronium, though flies are certainly capable of pollinating the open flowers and may be of special importance in forest dwelling and alpine species where bees are not always as abundant. Pendant flowers also have the advantage of being protected from rain. The pollen is dehisced over a relatively delayed period since the anthers don't open all at once. In general, three anthers will open first while three will open days after the first three. This lessens the chance that hard rain or wind will damage the pollen. The recurved tepals further protect the flower by closing or bending down in rain or in diminished sunlight, then opening up again when the sun comes out.

Erythronium oregonum ssp. leucandrum
Bulbs always seem to grow deeper than one would think, and digging wild plants is likely to kill them (besides being an unethical practice). Fortunately, Erythronium is relatively easy to grow from seed. Seed of most species can be sown in Autumn on the surface of the potting medium. As per advice from friend and bulb grower extraordinaire Ian Young, soaking the seeds overnight in water improves the first year germ rate. I have found this to be accurate, as seed I had acquired of a handful of species was successfully sown this way. Left outside throughout Winter, all of my Erythronium seed pots have germinated. I will allow them to grow on for another year before repotting them or planting them out into the garden. As stated, neither E. hendersonii or oregonum increase reliably vegetatively and are best increased by seed.

Erythronium hendersonii seedlings
A species from Eastern North America, yellow-flowered Erythronium americanum, has been heavily researched. In a handful of studies, mycorrhizal relationships between E. americanum and associated plants were examined. The most exciting discovery, in my opinion, was that bulbs (or as they say, corms) infected with arbuscular mycorrhizal fungi which enters the roots, unlike ectomycorrhiza which doesn't enter the roots, were found to be nearly twice as large as bulbs treated with fungicide. E. americanum produces roots in the Autumn, as do all Erythronium, and it is then that they are infected. Surrounding plants and trees, such as sugar maple (Acer saccharum) grow in close association with E. americanum and have been found to share mycorrhiza. Another interesting discovery was that E. americanum may help the establishment of young sugar maples by supplying them with carbon through the mycorrhizal network. Ian Young wrote a concise piece on the seeds of Erythronium, including how to grow them, found here: Erythroniums in Cultivation: Seeds (Ch.1). As an aside, the bulbs are supposedly edible, though I couldn't bring myself to eat something so beautiful (and I discourage anyone from eating wild or unfamiliar plants for ethical and safety concerns).

Erythronium hendersonii in habitat
I speculate that other species of Erythronium also participate in mycorrhizal networks, and that they benefit from the infection as well. Many of the trees and shrubs that grow in association with Erythronium hendersonii and E. oregonum benefit from or require mycorrhiza (Acer sp., Arbutus menziesii, Arctostaphylos viscida, Ceanothus sp., Quercus sp., Pseudotsuga menziesii, etc.), therefore it is not inconceivable that they too benefit from mycorrhizal associations.

Erythronium oregonum

Erythronium oregonum ssp. leucandrum, differentiated from the type by having white anthers.
I had recently discovered, entirely by accident, a small population of Erythronium oregonum ssp. leucandrum on a nearby mountain above a small creek. It was my first encounter with the species in Oregon, the wild, or anywhere. The air was moist, no doubt in result of the running water complete with a small waterfall, and it was cool. In small clearings of Arbutus menziesiiPseudotsuga menziesii, leafless Quercus, small groups of E. oregonum were awaiting discovery. There were a few individuals of E. hendersonii, though not many. There are conflicting reports of whether the two species hybridize. I didn't see any hybrids, though I did see the species growing in close vicinity. The more adaptable E. hendersonii ventured slightly into the woods, while the more picky E. oregonum was solely found in forest clearings.

Erythronium oregonum ssp. leucandrum, greenish reverse

Erythronium oregonum ssp. leucandrum with a dance fly (Empididae), a potential pollinator
Erythronium oregonum ssp. leucandrum, nectar guides
Erythronium oregonum ssp. leucandrum in habitat
Erythronium oregonum ssp. leucandrum
Erythronium oregonum ssp. leucandrum with Toxicodendron (no leaves yet)

Erythronium oregonum ssp. leucandrum in habitat

Erythronium hendersonii

Erythronium hendersonii and Apis mellifera
Since I have lived in Oregon, Erythronium hendersonii has been a favorite wildflower of mine. Compared to E. oregonum, it is more common in hotter and drier areas, and prefers forest edges to cool shady clearings. This could explain the lack of hybridization, the two seem to prefer distinctly different habitats. This year has been a particularly floriferous year for E. hendersonii, and it is the first year I've seen honeybees visiting the flowers. The typical pollinators, based on my observations, are species of Bombus and anthophorine bees. More photos and information can be found on the Pacific Bulb Society page: Erythronium hendersonii.

Erythronium hendersonii
Erythronium hendersonii
Erythronium hendersonii, an aging flower.
Erythronium hendersonii, one anther just beginning to open.
Erythronium hendersonii
Erythronium hendersonii, aphids on the scape.
Erythronium hendersonii, large and small morphs.
Erythronium hendersonii, anthers shorten after opening.
Erythronium hendersonii, true petals (inner) ridged, sepals (outer) mostly flat.
Erythronium hendersonii leaves.
Erythronium hendersonii, a particularly happy roadside cluster. I find this kind of growth uncommon.
Erythronium hendersonii nectar guides.
Erythronium hendersonii
Erythronium hendersonii
Erythronium hendersonii, interesting reverse coloration.


Alverson, Ed. "My Erythronium "Big Year"" Scottish Rock Garden Club. May 2006. 

Lapointe, Line, and Sylvain Lerat. "Annual Growth of the Spring Ephemeral Erythronium americanum as a Function of Temperature and Mycorrhizal Status." Can. J. Bot. 84.1 (2006): 39-48. 

Lerat, Sylvain, Rachel Gauci, Jean Catford, Horst Vierheilig, Yves Piché, and Line Lapointe. "14C Transfer between the Spring Ephemeral Erythronium americanum and Sugar Maple Saplings via Arbuscular Mycorrhizal Fungi in Natural Stands." Oecologia 132.2 (2002): 181-87. 

Owen, Travis, et al. "Erythronium hendersonii." Pacific Bulb Society. 2015. 

Young, Ian. "Erythroniums in Cultivation: Erythronium oregonum (Bulb Log 49)." SRGC Bulb Log. 9 Dec. 2015. 

Young, Ian. "Erythroniums in Cultivation: Erythronium hendersonii (Bulb Log 51)." SRGC Bulb Log. 23 Dec. 2015.

Wednesday, March 23, 2016

Arctostaphylos viscida

Arctostaphylos viscida
Arctostaphylos viscida Parry (Sticky whiteleaf manzanita) is seeing its best bloom in the past five years here in Southerstern Oregon. Manzanitas are in the family Ericaceae, which includes related genera Arbutus (madrone, strawberry tree), Calluna (heather), Erica (heath), Kalmiopsis, Pieris, Rhododendron (includes azaleas), Vaccinium (blueberries, cranberries, etc.), and over a hundred more genera, few of which known in cultivation. A. viscida is native from Southwestern Oregon south through most of California (to Kern County, possibly further south). It is a shrub or small tree, sometimes reaching a height of fifteen feet in optimal conditions, shorter further south. Small panicle-like clusters of urn-shaped flowers appear in Spring. The entire inflorescence is sticky, covered in glandular hairs, with glaucus leaves, thus the common name.

Arctostaphylos viscida, a variant with whitish florets
Sticky whiteleaf manzanita grows in association with oak (Quercus), madrone (Arbutus menziesii), various conifers (JuniperusPinusPseudotsuga), and Ceanothus among others. With many of these, it shares a variety of endo- and ectomycorrhizae, which are types of fungi which survive on or within the roots of a host and trade valuable nutrients (as well as increasing the surface area of the roots) for carbon and other exudates (root secretions). Dozens of species of mycorrhiza have been discovered in association with Arctostaphylos and associated plant species. Essentially, mycorrhizal fungi are symbiants which infect their hosts, but they benefit the plants in multiple ways and are necessary for the establishment and survival of countless taxa in the plant kingdom.

Arctostaphylos viscida is a pioneer shrub, entering the landscape in succession following grasses and other herbaceous plants. A. viscida paves the way for trees such as Douglas-fir (Pseudotsuga menziesii), and contributes to its establishment by hosting the necessary mycorrhizal fungi that Douglas-fir requires to survive. The same group of mycorrhiza also aids in the establishment of Arbutus menziesii, a relationship which may explain why madrone is so difficult to keep alive in cultivation (lacking the correct mycorrhizal symbiosis outside its native range).

Flowers of Arctostaphylos viscida
The flowers of Arctostaphylos viscida are similar to many (but not all) ericaceous plants such as ArbutusPieris, and Vaccinium by having fused petals forming an urn or cup, a stigma nearly twice the length of the stamen, and a ring of stamen surrounding the ovary and nectaries. When a pollinator enters the flower to imbibe nectar (assuming they enter the flower through the opening rather than biting a hole in the side), they first encounter the stigma before brushing past the anthers in an attempt to reach the nectar. While visiting the next flower, pollen is deposited onto the stigma before inadvertently collecting pollen from that flower. This ensures that the pollen is coming from separate flowers, which is good for overall fitness of the species.

Arctostaphylos viscida bark
The bark is similar to that of madrone (Arbutus menziesii): cinnamony, thin, and smooth once the outer layer of bark peels off. It has the unique characteristic of repelling water. This feature may contribute to the plants ability to survive in severe drought, though if there is inadequate rain or sun they do not flower well. Arctostaphylos viscida shrubs that grow on the north side of structures or under dense canopies of trees do not seem to flower reliably. The excessive shade from a northern exposure or tall trees promotes fungal infections that result in aborted buds and black spots on the leaves. A. viscida prefers open sunny habitats, and is more fit in chaparral than in dense woodlands, though it does perfectly well at forest edges, clearings, and slopes which in some respects have a similar ecology to true chaparral.

From left: A. viscida berries, crushed dried berries, and seed
Seeds of Arctostaphylos are produced in the form of berries. In A. viscida the berries are sometimes sticky, but this seems to go away when the fruit is mature. There is speculation that the berries (and seeds) are distributed by animals, probably birds. Laboratory tests of seed procured from coyote feces (what a fun job that must have been) found low germ rates. Birds are more likely, as the berries would likely pass through quickly (acid treatment in a lab helped break seed dormancy). Fire is another treatment that helps scarify the seed and break dormancy, and has the added benefit of reducing competition (especially tree saplings) which would otherwise shade out the slow growing manzanita. Suppressing fire is probably hindering the development of new colonies of manzanita. By briefly examining many of the stands in my area, it is difficult to find anything but mature plants 6' or taller. I sowed the seeds pictured above last Autumn, but have seen no signs of growth yet. It may take another year or two, and I may build a small fire over the pot to stimulate germination.

A honeybee (Apis mellifera), robbing nectar from a hole in the side of the flower.
Pollinators of many types visit the flowers. The plant exhibits a generalist pollination strategy, and is visited by a wide variety of pollinators. However, due to the shape of the flower (having a constricted opening), smaller insects (besides insects that are small enough to enter the opening) and short-tongued pollinators are excluded from performing as true pollinators and are instead more often seen stealing nectar by entering holes in the sides of the flowers. This likely reduces the chance that the defiled flower will produce fruit since the reproductive structures are bypassed, and the loss of nectar reduces the likelihood that the correct pollinators will be attracted to that particular flower, assuming the reproductive structures weren't damaged when the thief bit threw the side.

Just based on my direct observations, I have seen the following types of pollinators visit the flowers [though there are undoubtedly many more pollinator types throughout the entire range of A. viscida]:
  • Bees: Andrena sp., Apis melliferaBombus sp., Apis mellifera, and bees from the tribes Anthophorini and Eucerini.
  • Flies: Families Bombyliidae (Bombylius major), Empididae, and Scathophagidae.
  • Ants: Family Formicidae
  • Beetles: Family Coccinellidae
  • Hummingbirds: Selasphorus rufus
The smaller bees (Andrena, Apis, Nomada, etc.) will likely not be effective pollinators of Arctostaphylos. Flies in the families Bombyliidae and Empididae are likely effective pollinators due to the length of their probosces. Ants and beetles are unlikely to be effective, the former due to pollen damage from formic acid and the latter due to their herbivorous (flower and pollen eating) nature. Hummingbirds are likely to be effective pollinators, though they can damage floral parts in search of nectar and possibly thrips inside the flowers. Hummingbirds visit the flowers relatively infrequently and are probably second importance to the larger Bombus sp. and anthephorine bees (Anthophora or Habropoda). Other bees seen on the flowers of various species of Arctostaphylos (not limited to Oregon) include bees in the genera Osmia, Augochlorella, Lasioglossum, Halictus, and Eucera; wasps; flies (Eristalis and Volucella, Syrphidae); various Lepidoptera; thrips (Thysanoptera); and Anna’s hummingbirds (Calypte anna, speculated as feeding on thrips as well as some nectar). (See: Richardson et al. 2012, Eliyahu et al. 2015.)

A bumblebee (Bombus), collecting nectar legitimately.
Bumblebee queens are the largest and earliest Bombus to visit flowers. Though they are in the same family as honeybees (Apidae), bumblebees form annual colonies in which new queens endure Winter while the rest perish. Bombus tend to be large robust bees with long probosces and are able to fly in cool and cloudy weather, conditions which are unsuitable for honeybees. Their long tongues enable them to reach the nectar of most flowers quite easily. However, they have strong mandibles and are known to be nectar robbers in many plant species, namely by biting holes in the sides of flowers. While I did not witness nectar thievery by any bumblebees on the Arctostaphylos, there are some pollinators which will gather nectar legitimately (without defiling the flower) while other individuals of the same species exhibit thievery/robbing, so there is still a possibility that bumblebees are the hole-biters. However, the flower walls of A. viscida are weak and it is possible that small bees (Andrena, perhaps) are in fact the ones biting holes in the flowers. Close observation is needed to determine the truth.

Aside from suspected thievery, Bombus and anthophorine bees are known to vibrate their flight muscles to A.) warm their bodies in the absence of sunlight or warmth and B.) dislodge pollen from the anthers of the flowers they visit (buzz pollination), which is by far more efficient than brushing on the anthers with their bodies as most bees do. Add to this the minute electric charge possessed by both flowers (grounded, negative charge) and bees (positive charge, a trait shared with all insects). Pollen jumps from the anthers to the bee once it is vibrated off the anthers. Bees which pollinate utilizing buzz pollination, I deduce, are probably the most significant pollinators for Arctostaphylos, perhaps for all species.

Andrena sp., robbing nectar.
It's pretty clear from this image that this bee is robbing nectar from a hole in the flower. Most likely, the hole was already there and the bee was taking advantage of it, but further observation is needed to confirm that claim. Andrena are small bees, and though the flowers of Arctostaphylos aren't particularly protected, it is still unlikely that these small bees are the hole-biters. I would be interested in your observations if you are in a position to observe at all.

Andrena sp., robbing nectar.
Another consideration, the smaller bee genera (Andrena, Nomada, Apis, etc.), as compared to Bombus and anthophorine bees, appear morphologically unable to access the nectar legitimately due to the very constricted opening of the flowers of Arctostaphylos viscida. This, then, results in the small bees to seek out the holes to access the nectar rather than attempt to find flowers with wider openings. This may seem detrimental to the plant, but it could be that the loss of nectar due to robbing in many of the flowers actually incites legitimate nectar collectors to move between flowers more often, which potentially results in more pollen being transferred between more flowers.

A dance fly (Empididae) and Andrena.
Dance flies (or dagger flies, Empididae) are very frequent visitors of Arctostaphylos viscida, and move between flower clusters quite frequently. Their long proboscis is used both to eat prey (typically smaller flies) as well as for foraging on flowers. They do probably contribute to pollination since they visit so many of the flowers, though they are hardly likely to be as efficient as bees in this regard as little pollen is likely to adhere to the proboscis rather than the hairy bodies of bees.

A bee fly (Bombylius major, Bombyliidae) feeding on nectar
Bee flies (Bombylius, Bombyliidae) are frequent visitors of the flowers and move between flowers quite frequently. They hover over (or in this case under) flowers to feed on nectar. I'm not convinced they contribute to pollination very efficiently despite their frequency, though they may contribute to the efficiency of bees by drinking nectar and encouraging bees to visit more flowers in search of nectar. Bombylius major is a widespread species. While adults visit flowers for nectar, the larvae are parasitoids of ground nesting bees (and maybe wasps). Eggs are dispersed near the entrance of a ground-nesting bees nest (Andrena, for example), and the larvae enter the nest and feed on the bee larvae, and perhaps the stored pollen. Even though they harmful to ground nesting bees, their presence can signify a healthy host population.

Winged ant ♂
Winged ants, superficially similar to tiny wasps (like the tiny Chalcid wasps), are common visitors to flowers. They are distinguished from wasps by their elbowed antennae (I apologize for the photo), wasp antennae do not have 90° bends. They are defferentiated from termites by the constricted waste, similar to a wasp. It is unlikely they are of any consequence as pollinators, though I doubt their presence is harmful in any way. Flying ants are the reproductive members of an ant colony, sent off to mate and go on a doomed quest to start a new colony, although their chances for success are slim since they will probably die of starvation, dehydration, or as food for birds or other insects. In this regard their presence is good, there is now a food source for another insect or bird (hummingbirds, perhaps) which in turn is beneficial for everyone.

Ants are fairly common on the flowers of Arctostaphylos, but due to their small size in this case they are unlikely to contribute to pollination. As with other plant species (such as Iris chrysophylla) ants seem to coalesce on select inflorescences or clusters of flowers, while they may be absent from others. They are usually nectar thieves, though some have been found to contribute to pollination in some plants (and are the primary pollinators of a handful of orchids). The presence of antimicrobial secretions of varying potency in most ant species argues that pollen viability may be compromised. Consider, also, that they are (mostly) wingless and do not travel much between flowers, and are mostly hairless so pollen does not adhere well to their bodies. In some cases they may even fight off other insects that attempt to visit the flowers they are foraging upon, or most likely their presence deters pollinators from attempting to forage there at all, something I've observed directly.

Studying my photo, it seems viable that if the flowers did not have holes in the sides the ants may just contact the anthers when accessing the nectar, and upon entering another flower they may just contact the stigma since the entrance is so constricted. If I were to test this I would use some type of mesh that would have holes large enough for the ants to pass through, yet small enough to exclude larger pollinators. The mesh would be used to bag multiple flower clusters (the more the better) with flowers that do not have holes in the sides. I would assign numbers to the clusters, and observe them for the presence of ants, and proceed to observe which (if any) produced fruit. Testing viability of any seed produced would also be important. I would be happy to hear of anyone else's observations of ants on the flowers of any species of Arctostaphylos, I will add them here.

A predatory wasp


Acsai, Jan, and David L. Largent. "Fungi Associated with Arbutus Menziesii, Arctostaphylos Manzanita, and Arctostaphylos Uva-ursi in Central and Northern California." Mycologia 75.3 (1983): 544. 
Armstrong, W. P. "Termite, Winged Ant, Small Wasp or Gnat?" Ant Genera Index. Wayne's Word, 2013. Web. 
"Calflora: Arctostaphylos Viscida." Calflora: Information on California Plants for Education, Research and Conservation, with Data Contributed by Public and Private Institutions and Individuals, including the Consortium of California Herbaria. 2016. 
Clarke, D., H. Whitney, G. Sutton, and D. Robert. "Detection and Learning of Floral Electric Fields by Bumblebees." Science 340.6128 (2013): 66-69. Web. 
Eliyahu, Dorit, Andrew C. McCall, Marina Lauck, and Ana Trakhtenbrot. "Florivory and Nectar-robbing Perforations in Flowers of Pointleaf Manzanita Arctostaphylos Pungens (Ericaceae) and Their Effects on Plant Reproductive Success." Arthropod-Plant Interactions 9.6 (2015): 613-22. Web. 
Eliyahu, Dorit, McCall C. Andrew, Lauck Marina, Ana Trakhenbrot, and Judith L. Bronstein. "Minute Pollinators: The Role of Thrips (Thysanoptera) as Pollinators of Pointleaf Manzanita, Arctostaphylos Pungens (Ericaceae)." J Pollinat Ecol. 16 (2015): 64-71. Web. 
Fryer, Janet L. 2015. Arctostaphylos viscida, sticky whiteleaf manzanita. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). 
Horton, Thomas R., Thomas D. Bruns, and V. Thomas Parker. "Ectomycorrhizal Fungi Associated with Arctostaphylos Contribute to Pseudotsuga Menziesii Establishment." Can. J. Bot. Canadian Journal of Botany 77.1 (1999): 93-102. 
Lewis, Donald. "Why Do Some Ants Have Wings?" ISU Extension News Release. ISU, 22 July 2002. Web. 
Moncada, Roberto. "Pollinators and Nectar Robbers on Manzanita (Arctostaphylos Sp.)." Amateur Biology Blog. 07 Feb. 2013. Web. 
Rostás, Michael, and Jürgen Tautz. "Ants as Pollinators of Plants and the Role of Floral Scents." All Flesh Is Grass Cellular Origin, Life in Extreme Habitats and Astrobiology (2010): 149-61. Web 
Shirley, C. 2011. "Plant Guide for sticky whiteleaf manzanita (Arctostaphylos viscida)". USDA-Natural Resources Conservation Service, California Plant Materials Center, Lockeford, CA 95237 
Turner, Mark. "Arctostaphylos Viscida | Sticky Whiteleaf Manzanita." Wildflowers of the Pacific Northwest. Web.

Saturday, March 19, 2016

Floral Visitors 18

Muscari armeniacum with a honeybee
Pollinators of all kinds have been out, particularly bees who are taking advantage of the introduced species in my garden. Muscari is in full bloom, attracting gangs of honeybees. Last year I witnessed a variety of other floral visitors such as plume moths (Pterophoridae), geometrid moths (Geometridae), anthephorine bees (tribe Anthophorini), and other small arthropods. They don't seem to increase very well here, perhaps the soil is not to their liking or it dries up too quickly after the Spring rains cease. Most of them are planted out in native soil, rather than a raised bed where I grow most of my perennials. Perhaps they would benefit from a fall application of leaves to encourage some microbial activity (thus stimulating quicker nutrient cycling).

Scilla siberica
The bulbs of Scilla are sometimes considered to be irritating when handled by some people, and my assumption was that the assumed irritating constituents would also deter animal pests. Deer surely ignore them, yet voles are seemingly unaffected. Last year, I had a lot of Scilla siberica planted around and it had been a reliable resource for honeybees and bumblebees. However, this year has seen a drop in the number of flowering plants and honeybees have not been observed visiting them. Still, this wont keep me from attempting to grow more, next time I'll just use mesh baskets or wire cages, a necessary pain in the a**.

Chionodoxa luciliae (syn. Scilla luciliae)
The Chionodoxa, now widely accepted as Scilla, are like S. siberica and now are few in the garden. Yet, these tiny blue flowered bulbs have swooned me and I will continue to plant them into the garden, next time with underground protection. The pollen of Chionodoxa is not as exposed as Scilla, perhaps an adaptation to prevent damage or loss of the pollen from rain. It may just be a coincidence, but it seems bees are less interested in Chionodoxa than Scilla (sensu stricto) which have highly available pollen and nectar. Bumblebees were spotted visiting Chionodoxa last year, perhaps because they possess probosces that are robust enough to push between the anthers to reach the nectaries within.

Hyacinthus orientalis with Mecaphesa, a bee predator.
Hyacinthus, the common hyacinths sold alongside tulips and daffodils in the fall, are highly attractive to honeybees even when planted in small quantities, unlike the other scillas. I have a handful of hyacinths planted under a native wild lilac, aka deerbrush (Ceanothus integerrimus). Ceanothus are good for beneficial soil dwelling microbes, and are known to fix nitrogen, a result of a symbiotic relationship with some type of soil dwelling fungi. The plant trades something (root exudates), and in return receives nutrients or something similarly useful from the fungi. This in turn benefits everything growing in the vicinity because nutrients that would otherwise be unavailable to plants for one reason or another are being made continuously available by microbial activity. Hyacinthus orientalis are known to be heavy feeders, and will dwindle over time in less than adequate soil. Yet here under the Ceanothus, they are thriving! (Learn more about nutrient cycling here.)

Anemone blanda
Similar to the Hyacinthus, Anemone blanda is similarly attractive to honeybees even though there are relatively few of them and they are not planted near each other. Unlike hyacinths, the main appeal here is for the pollen. Besides honeybees, a variety of bumblebees and flies (Syrphidae, probably other families too) also visit these flowers. It is uncertain as to whether or not they produce nectar, or if they do it may be in a very small quantity and highly dependent on the growing conditions (including aspect). In general, when plants are grown in less than optimal conditions, the first thing they'll do is cease nectar production, survival comes first. Pollen, however, is much more important to a plant since it is required to create the next generation of plants. Pollen is also highly important to bees this time of year because it is the sole source of protein for developing larvae, nectar and honey being reserved for adults who require high amounts of carbohydrates to fuel flight and other tasks important to survival. (A fun/appetizing fact: wasps utilize other insects as the protein source for their larvae instead of pollen. Bees are basically vegans while wasps are largely predators/carnivores, though the adults of both feed on nectar.)

Hepatica acutiloba
Closely related to the genus Anemone, and often considered to be included in it, the single Hepatica in my shade garden attracts few to no pollinators. Though beautiful, it has some factors working against it when it comes to pollinator attraction. First, it is grown in shade while bees prefer to work flowers in the sun, especially this early in the year when the days are still very cool. Second, there is only one. A single flower of any plant is highly unlikely to attract anything, except for a photographer. Bees and other pollinators are more attracted to groups of plants (Xerxes Society studies suggest single species plantings of 3×3' or larger to be most effective), and are most attracted to groups of single species rather than mixes. However, I do find that having a mix of flowers does attract a wide range of pollinators nonetheless. I do plan on acquiring more Hepatica for my shade garden, as well as more flowering plants for my shade garden to entice more pollinators into the dark.

Crocus vernus
A lone Crocus stands under Pinus ponderosa, where dozens of other crocuses were planted and many were uprooted by both deer and turkeys. As the year progresses, fewer and fewer crocuses are to be seen and fewer and fewer are likely to be visited by pollinators in my garden. This is probably due to the increase in competition and the decrease in the population of the crocuses rather than their general appeal. I strongly believe that if I had a field of the latest blooming Crocus they would be crawling with pollinators (and probably also filled with deer, voles, turkeys, and other herbivores). This is probably the last look at Crocus for the year, unless my saffron decided to bloom this year.

Viola odorata and Vinca minor
I have worked hard to build up a thriving community of plants in the small raised bed around my well house, and the work has paid off. Vinca minor, a close relative to the highly invasive Vinca major (which coats entire riparian banks and shady hillsides that are too dark for Rubus armeniacum), grows happily along with dozens of other small plants. Much of what grows here now was sown as seed, some planted as offsets. Roots from nearby Pseudotsuga menziesii invaded these beds quickly after they were established, and brought with them myriads of fungal hyphae. At first I thought this was a horrible thing, and I had attempted to eradicate the beds of the intruders, a futile task since there is a 100' tree less than ten feet away. Now I see that the plants growing there now have no issue competing with the tree roots, and I hypothesize that the fungal network has brought with it a diversity of other microbes which are supporting the growth of the plants.

Microbes sequester nutrients which could otherwise be lost due to watering or rain and delve deep out of the reach of plant roots. These nutrients are eaten by microbes, sequestered in their bodies, and released when the microbes either die of natural causes or are eaten by other microbes, thus making them continuously available to plant roots. So a diversity of microbes is a good thing. The microbes are supported by a diversity of plants, all of which release different exudates (the closest thing to plant poop) into the rhizosphere (the area just around the roots) and feeding the microbes. Many microbes occupying the rhizosphere feeding on exudates can crowd out pathogenic microbes and prevent disease in plants. The benefits go on and on.

Now back to Vinca, they are reportedly bee pollinated, though I have made no such observation. The blue flowers are nice though, and with all of the competition I doubt the plant will get too out of hand.

Viola odorata
Sweet violets are very satisfying to me. They grow very well here, require no Summer irrigation (though they flower better with it), and are happy in sun or shade. Bees appreciate the flowers, and where they are prevalent can be detected from afar by their sweet scent. They also like to spread, so it is worth taking the time to consider their placement before introducing them to your garden. If you have a lawn or a large patch of bare ground, say, under a tree, they'd be perfect! They don't require pollination to set seed, and will spread by runners, so a sizable patch may be formed in a short period of time.

Lamium maculatum
Another very easy plant that is attractive to bees, Lamium maculatum grows in the sunny corners of the raised beds surrounding my well house. It is a low growing maintenance-free creeper that can tolerate a lot of drought when established, is ignored by deer, and unaffected by mole/vole tunneling. Bumblebees are most interested in the odd reptilian-reminiscent flowers, though honeybees will occasionally frequent them.

Further Reading:

Lee-Mäder, Eric, and Marla Spivak, eds. Attracting Native Pollinators: Protecting North America's Bees and Butterflies: The Xerces Society Guide. North Adams, MA: Storey Pub., 2011. Print.

Walker, Travis S. et al. "Root Exudation and Rhizosphere Biology". Plant Physiol. Vol. 132, 2003.