West Coast Late Season Pollinator Plants

By: Travis Owen

Autumn is here, the days are warm, the nights are cool, and bees and other pollinators are still active.

For me this is one of the best times of the year since we can finally get some relief from the intense heat of Summer, and the leaves begin to change color on the trees. For bees, particularly honey bees, it is a crucial time to collect as many resources as possible so they can survive the Winter. For solitary bees and other pollinators, most of which do not live in colonies or over Winter as adults, nutrition is kept up in mating individuals and stores for brood are collected so the species may live on another year. For many of us gardeners, we love to see and support these creatures. This means reducing or eliminating the use of pesticides and providing them with good nutrition: flowers.

As a general rule, native flowering plants (although occasionally less showy) are far more useful to pollinators than exotic plants since the native pollinators have coevolved with them since time immemorial. Foreign plants, even those from a different region of the same state, generally do not attract the same diversity of pollinators, however, they may be highly attractive to a select few pollinators. I personally am not “strictly native” when it comes to gardening, so I grow many nonnative plants. I do appreciate the value and importance of natives, having seen firsthand the pollinators they attract that aren’t attracted by exotic plants. This, in a sense, strikes a balance between gardening for conservation and gardening for aesthetics. Of course, for me, I am always gardening for pollinators.

Madia elegans is one native wildflower that is just beginning to enter gardens. The flowers are open from dusk til dawn, and will remain open longer if grown with a Northern exposure or on cloudy days. They are highly attractive to honey bees and a variety of other bees and other pollinators, though for conservative gardeners they may appear a bit weedy and untidy.

Read more about Madia elegans and its various pollinators (Owen 2016).

Euthamia occidentalis is a native goldenrod, occasionally sold in nurseries, and is used for erosion control. It can be grown in damp places, something I have seen firsthand on the bank of the Rogue River. Like the true goldenrods (Solidago spp.) they are highly attractive to bees, as well as various wasps. I observed honey bees and halictid bees visiting the flowers. Sphecid wasps, Prionyx sp. I think, were also seen. Species of Prionyx paralyze grasshoppers as live food for their offspring in underground brood nests.

Chicory is one of those nonnative plants that is found nearly everywhere humans are, a truly successful species. They are closely related to lettuce, and like lettuce have flowers that are open for a single day (often only in the morning) before withering. New flowers open daily, and attract honey bees and other bees, as well as other pollinators (like grass skippers, Hesperiinae).a composite, each stalk seen in this photo is an entire flower complete with staminate and pistillate parts, while the “petals” are actually sterile ray florets whose purpose is to attract and provide a landing pad to pollinators.

Read more about Cich orium intybus (Street et al. 2013).

Related to chicory, in the sunflower family (Asteraceae), yellow starthistle is another nonnative plant which is adored by honey bees and beekeepers alike. Unlike chicory, which is unofficially considered to be a benign exotic by most, Centaurea solstitialis is on the noxious weed list in Oregon and at least 10 other states and two Canadian provinces. Despite this, it is loved by beekeepers since it gives honey bees a lot of resources to make it through Winter, since this region is generally considered to be in a dearth of nectar from mid-Summer onward. I challenge this view, considering there are at least a few other plants, native and exotic, which are worked by bees and flower en masse in the latter half of the year (i.e. Madia elegans & Hypochaeris radicata, the latter another noxious nonnative adored by bees).

Yellow starthistle is native to southern Europe and western Eurasia, and in some parts of its native and introduced range is considered to be a supreme honey plant as the honey produced from it is one of the most sought and most popular varietal honeys according to some sources. The plants are self-incompatible, thus requiring insect pollinators. Honey bees account for most of the seed set, bumblebees following in importance. The apiary above was surrounded by a portion of uncut starthistle in Ashland, Oregon. The hills of Ashland are completely filled with this invader, showing the true destructive nature of noxious weeds, whose extreme competition outcompete native wildflowers and disrupt the natural balance. And in case you were wondering, I had to work all 50+ hives in this apiary, and thanks to the thorny inflorescences, it was quite literally a pain in the ass (among other places).

Read more about Centaurea solstitialis (Zouhar 2002).

True thistles, such as bull thistle (Cirsium vulgare) are considered noxious weeds in Oregon and several other states. It is found in all fifty states of the U.S., yet native to Europe, Eurasia, and Africa. The plants are worked by honey bees and bumblebees, possibly others, though they often grow in very low density in this area so are not worked judiciously. They are known to grow in dense stands and I would presume that they would be quite covered in bees. The thorns are incredibly sharp and easily penetrate clothing and skin, which I can say is quite painful!

Another nonnative weed, quite widespread, the perennial sweet pea was once introduced to prevent erosion in ditches and banks. Fortunately, it is worked by a variety of bees including honey bees, bumblebees (Bombus spp.), large carpenter bees (Xylocopa spp.), and leaf-cutter bees (Megachile sp.). Peculiar, this nonnative pea is the only flower I have seen the leaf-cutters on. Except for the carpenter bees, all the bees I have seen appear to rob nectar by accessing it from above the nectaries rather than passing through the anthers, though these plants may very well be self-compatible like the garden pea since they seem to produce full pods most of the time (if not all the time).

Mullein (Verbascum spp.), occasionally “cowboy toilet paper” (I haven’t, so don’t ask), is an ubiquitous roadside weed, probably all over the country. Typically when one speaks of mullein one is speaking of Verbascum thapsus, or common mullein, which has a single flower spike and can reach seven or eight feet in height. A less common species, at least in my area, V. olympicum differs from V. thapsus most obviously by the multi branched inflorescence atop the plant, which attains a similar height. The individual flowers of V. olympicum appear to be slightly larger than those of V. thapsus, and the flowers of the latter seem to close or wither quicker than the former.

Both V. thapsus and V. olympicum, in my experience, are decent bee plants, though V. thapsus seems to only be worked in the morning when new flowers open, while V. olympicum seems to be worked all day. Another weedy mullein commonly encountered, V. blattaria, or moth mullein, is only occasionally worked by bumblebees but rarely honey bees, or at least I haven’t seen it. All are grown in gardens, sometimes for their medicinal properties (the flowers of V. olympicum and V. thapsus are used for tea, and the plants are a source of water soluble saponins and mucilage).

The tall evening primrose, similar to some of the species native to Oregon, is one of many species grown in gardens. As the name implies, the plants can get really tall, up to four feet in the case of the plant photographed. The flowers open at dusk and remain open until morning when they wither. Though each flower is only open one night, new flowers open daily. They are primarily pollinated by large crepuscular sphinx moths (Sphingidae), some have visited this plant on more than a few occasions though I was unable to attain a photo. Honey bees adore it, as you can probably tell, and can be seen visiting the flowers as they open on warm nights, or in the morning before the flowers wither. There are hybrids of some of the smaller oenotheras available (i.e. Oenothera kunthiana), though they do not appear to be as attractive to pollinators in my garden.

Many milkweeds are useful bee plants, though the flowers of some species can pose a threat to bees and other pollinators (more on that later). Milkweeds are important honey plants in much of the U.S. where they are common. They are also paramount to the survival of many species of butterflies, including the monarch (Danaus plexippus) and other milkweed butterflies (Danainae) since the caterpillars of these butterflies are completely dependent on them for sustenance. Certain species of moths and a few true bugs are also dependent on milkweeds for survival.

Read more about milkweeds as honey plants (Krochmal 2016).

Milkweeds are peculiar plants for a variety of reasons. For an amateur botanist, I find their breeding system intriguing. The most notable feature of this, I think, is that the pollen is in the form of pollinia, as is found in orchids, where the pollen from each anther is composed into a single sticky mass. This mass adheres itself to the foot, or anywhere on the pollinator before being hooked onto the “claws” surrounding the pistil. Some unfortunate pollinators whose feet have pollinia attached become stuck themselves on these hooked appendages (called horns) and not having the strength to escape, die of dehydration or something similar. Butterflies, often being larger and more powerful fliers, can probably escape the horns quite easily, but bees, beetles, and wasps have been found hanging, dead, on the flowers of some species.

Read more about the Fatal Attraction of Milkweeds (Chen 2006).

In dry sunny fields, an inconspicuous plant in the Euphorbiaceae forms tight grey-green cushions of hairy foliage and tiny inconspicuous flowers. This is Croton setigerus, or turkey mullein, found in much of the Western U.S. in dry hot sites. It is occasionally worked by honey bees, and claimed to produce a “thick amber honey.”

Read more about Croton setigerus (Owen 2016).

Trichostema is a genus in the Lamiaceae, or mint family. A few of which are notoriously bee pollinated, such as the perennial California native T. lanatum, woolly blue curls, which is widely proclaimed to be a good honey plant. In my region, the annual T. lanceolatum is a somewhat locally common plant that grows in poor soil with low grasses and other small forbs. In my experience, it is more frequently visited by skippers (Ochlodes sylvanoides) who appear to be a good fit for the plants highly elongated reproductive structures.

Pollinator visitation, it seems, is a highly regionally specific variable. This has been seen in many other plants, and can readily be studied by any gardener who grows nonnative plants. In the case of Trichostema, where I have witnessed butterflies, many other people have reported seeing various bees visit the flowers of T. lanceolatum and there is similar literature on bee pollination of T. lanatum. Aside from bees, hummingbirds have been observed on some species, probably another regionally variable observation. To me, this speaks of the adaptability of some species to overcome the boundaries of others, in this case perhaps an inadequate supply of bees (not specifically due to bee losses, but maybe the normal ebb and flow of native bee activity in this area, correlating with the diversity, or lack thereof, of flowering plants at any given time).

Read more about Trichostema lanceolatum (Owen 2016).

In the garden, mints and their relatives are a sure thing when it comes to bee plants. I do grow a variety of mints, all in one corner of the yard since they can be so invasive, and the flowers do attract a variety of bees. I prefer the more well behaved mint relatives, such as Agastache and Nepeta. Common catnip is a short lived perennial that has survived with little care at the border of my garden for four years now. It was started by seed scattered onto disturbed soil and watered for the first year. Now it is four feet tall and covered in small flowers. Many species of native bee are attracted to the flowers, such as Lasioglossum and Bombus vosnesenski. Honey bees also adore the flowers, there may be upwards of 50 bees on this single plant at any one time.

Another “mint,” thyme is always attractive to honey bees. The particular selection T. serpyllum ‘Elfin’ appears to be later blooming than the others in my garden, and is an excellent plant in my small rock garden. Thyme is the source of the thymol, an antimicrobial compound used for the control of Varroa mites (Varroa destructor) among other things. There is a folk tale that where thyme is grown for seed at the field scale the honey bees nearby are free of mites. I cannot speak to the legitimacy of this claim, but the notion that very small quantities of thymol or other mite-repellent compounds are found in the nectar is not without merit.

While talking about Autumn bee plants, it is worth noting some of the bees cousins that are also highly active at this time. Aerial yellowjackets and bald faced hornets (both in the genus Dolichovespula) are predatory social wasps which build enclosed paper nests in trees or sometimes under overhangs of human made structures. At best, they are predators of garden pests such as tomato hornworms (Manduca quinquemaculata) and others, but at worst they are bee predators who can destroy weak honey bee hives. For strong hives they are merely a nuisance.

Practices to help your hives protect themselves include using the smallest opening of an entrance reducer, maybe a one inch entrance hole, and feeding your bees (inside the hive is best, i.e. hive top feeders or some variant) so they build in number and strength to ward off any potential intruders. Yellowjacket traps can be useful where they are very populous, but I would suggest using a hot dog or lunch meat as bait rather than the commercially available bait. I don’t usually condone the killing of hymenopterans, even wasps, but to be sure with simple traps (a chemical free approach) their populations will not be devastated and they will probably bounce back the following year.

To avoid ending on a gruesome note, here is one more good group of bee plants: Colchicum. Sometimes referred to as the autumn crocus, this name is a poor representation of the genus since there are autumn, winter, and spring blooming species in both Colchicum and Crocus. Colchicum, unlike Crocus, grows from a toxic structure that is like something between a bulb and a corm, quite unique, although typically considered to be a corm. Crocus on the other hand grows strictly from a corm and is not toxic, in fact it is practically edible and it is eaten by rodents, deer, turkeys, and slugs. Colchicum is virtually pest free, due to the toxins within the plant. Most of the commercially available colchicums are the autumn blooming types. These tend to flower in the fall, and send up leaves and seed pods in spring. I’ve grown colchicums for three years, and honey bees seem to adore them.

I grow four varieties including three Fall blooming and one Spring blooming although the Spring blooming type hasn’t grown to flowering size yet. The first variety I attained was the hybrid C. ‘Lilac Wonder,’ a commonly available and very popular large flowered hybrid supposedly between C. giganteum and C. bornmuelleri (both sometimes considered synonyms of C. speciosum), bred sometime in the early 1900s. I also grow C. speciosum, which has slightly smaller flowers and is shorter, but equally if not more beautiful.

Of the few colchicums that I grow, C. cilicicum is by far the most floriferous and longest blooming, thus the best for bees. The individual flowers don’t last very long, but C. cilicicum sends up new flowers in succession for a few weeks. Despite there being so few of these flowers, there is a continuous stream of honey bees visiting them for both pollen and nectar. I imagine a field full of Colchicum would be quite active with bees of various types. I would do just that, but the cost of these large bulb/corms is somewhat prohibitive for me. I am attempting a few species from seed, and have a hopeful view of the future.

There are many other Fall blooming plants that may be excellent bee plants. Some recommended by others include Aster spp., Caryopteris spp., Clematis ternifolia, Epilobium spp., Eutrochium spp., Hylotelephium spectabile, Lythrum salicaria, Perovskia atriplicifolia, Pycnanthemum flexuosum, Rosmarinus spp., Tetradium daniellii, Vernonia altissima, Vitex agnus-caste, and no doubt many others. I’d love to hear about more bee plants, put them in the comments (with your location for context)!