A photo investigation of favored Willamette Valley, Oregon butterfly nectar plants
Find out which species of plants appear to be most important to support butterflies in the adult phase of their life cycles. This list is specific to butterflies in our Willamette Valley bio-region.
Summary: the following appear to be the most common nectar plants used for a wide variety of adult butterflies in our area: Milkweed and closely related Dogbane, all aster family plants (particularly Aster, Senecio, Pearly Everlasting, Thistle, Erigeron/Fleabane, Yarrow, Goldenrod), Buckwheats, Pea family (Vetch, Vicia, Pea), Valerian, Potentillas, Verbenas, Mustard, Fiddleneck, Popcorn Flower, and Penstemons. Other plants that are not native to our area, but are native to the areas where the butterflies are also native: Echinacea, Zinnia, Joe-pye weed, Black-eyed Susan, Liatris, Bee-balm and Scabiosa.
For caterpillar host plants, see this post.
About a year ago I wrote a post outlining Willamette Valley (in Oregon) butterfly nectar plant associations. This information was based on all of the butterfly literature that is available to me, from my butterfly books or on the Butterflies and Moths website. But something was bugging me about the way that the information was presented - I wasn’t clear on whether those associations were based on objective data gathered, or just the author’s personal observations. I wondered if there was a way that I could collect more objective data.
I had a feeling this was an important project based on my observations in the garden. I’ve been noticing strong preferences. Swallowtails always seem to come to milkweed and rhododendrons. Woodland skippers are always coming to my lavender, germander, and oregano plants. The Clodius Parnassians are always seeming to flutter above my ninebark, and over this last summer I kept seeing them repeatedly visiting buckwheat. Even though there were plenty of other flowers available to them, they always seem to go back to what they like, and those preferences are consistent year to year.
Over the winter I decided I would do a little more investigating and came up with an idea of collecting data. I pulled up the Butterflies and Moths website and looked up each species that is likely to occur here in the valley, and observe the butterfly nectar preferences in the photos.
I wanted to find out: are there important floral resources being overlooked in butterfly and native plant literature? And are there important plants not in cultivation? The answer, I’ve come to find out, is a resounding yes.
Roughly 5,000 photographs of butterflies feeding on flowers that I could identify were catalogued by me. Though I collected data on photos around the U.S. for species that are known to inhabit the Willamette Valley, I did not include flowers that would obviously not grow here. I also did not include flowers that I could not identify (there were not many). Asters and fleabanes were hard to tell apart in the photos and weren’t always identified by the observer - those that bloom early in the season were more likely to be fleabanes, while the later season ones more likely to be asters. Regardless - both are important plants.
The observations lined up fairly well with what was reported in the literature, but there were several plants to consider in addition to those. The raw “data” is too much to list on a single post, but you are welcome to view it here.
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Takeaways:
Takeaway #1: the aster or composite family of plants comprised about 50% of observations. All sorts of plants from this family are used with various bloom times.
Takeaway #2: Dandelion or those that look like dandelions (I call them dandelion-ish) were the second highest flower count. Many of these were straight up dandelions, but some of them certainly could have been closely related native or other weedy species. I will be trying to become more familiar with these plants. I wonder if Agoseris species would fill that niche in the native plant garden. And… I won’t be targeting dandelion for removal in my garden unless they genuinely become problematic for some reason.
Takeaway #3: there were many photos of what looks like Senecio AKA Groundsel. They are the most common native composites used after asters. Some of them were identified as such by those who took the photos, but others I had to guess as I could only see the flowers. Some of the photos look like they could be Western Goldenrod or closely related. Note that the Cinnabar Moth was released in Oregon to control tansy, but that Moth will also eat native senecios. Senecios need our help.
Takeaway #4: other Aster family plants that are heavily used: Aster, Pearly Everlasting, Yarrow, Fleabane, Goldenrod, Thistle (yes, there are native thistles but). Note: aster family plants have very different bloom times and a wide offering would be preferred. About half of our species of butterflies are finished flying by the time asters and goldenrods are available in late summer.
Takeaway #5: there are many Aster family plants that aren’t native to our area that are used. When I looked into the butterflies that nectar on them, they are native to the areas where those plants are also native to. Examples: Echinacea, Zinnia, Joe-pye weed, Black-eyed Susan, Liatris. Outside of the aster family, another important plant not native here (but also grow indigenous to where the butterflies are also native to) is the purple flowering Monarda (Beebalm). Another is Scabiosa. In some native plant circles these would be scorned. But to my knowledge, none of these non-natives to Oregon have escaped garden situations.
Takeaway #6: one of the highest used plant is butterfly bush. That’s too bad - butterfly bush is awfully tempting to plant, but it is quite invasive here and chokes out native vegetation. However, butterfly bush is in the same family as penstemons. Penstemons - mostly native varieties - were used in 19 of the photos I reviewed, whereas butterfly bush was seen in 240 photos. I wonder if the very long bloom time of the butterfly bush (as opposed to the short bloom period of penstemon) along with the ubiquitous butterfly bush plantings accounted for the difference in how often the plants are used. I know there are sterile cultivars of butterfly bush available - but last I heard is that the jury is out on whether they are reliably perennial and whether they still have invasive potential.
Takeaway #7: early blooming yellow mustards are important. I wonder if American Yellow Rocket would fill that niche.
Takeaway #8: Popcornflower, Fiddlenecks, and the occasional Mertensia were somewhat important from the Borage family.
Takeaway #9: Sitka Valerian was observed in quite a few photos.
Takeaway #10: Plants in the pea family were highly used as nectar sources. These were clovers (mostly non-natives observed), as well as native Vetches, Vicias, wild peas.
Takeaway #10: all manner of Buckwheats are favorites for a wide variety of butterflies.
Takeaway #11: plants in the Apocynaceae are top picks for all butterflies. Milkweeds were the single most commonly used plant and Dogbanes were also highly used. Milkweeds aren’t just for Monarchs!
Takeaway #12: Potentillas were highly used in the rose family, as were blackberry flowers (sadly most of the blackberries seen were of the invasive kind).
Takeaway #12: in the Vervain family, Verbenas are super important, some of which are native. Lantanas - closely related to verbenas - were seen being used even more often and are commonly used as a garden bedding plant.
Takeaway #13: Mock Orange and red Columbine are favored food sources of Western Tiger swallowtail and Pale Tiger Swallowtail. Strangely no other butterflies are seen on these species in the photos. Western Tiger Swallowtail is probably the most common butterfly seen in the Portland area.
Last, but not least takeaway: nectar preferences appear to be fairly strong, and caterpillar host plants are the least favorites used for nectar (with a few exceptions). Host plants are for sure important for their caterpillars, but without adult nectar food, butterflies can’t fly or reproduce.
Willamette Valley butterfly nectar source summaries
**The asterisks are denoting which species are less likely to be seen in the valley, more common in higher elevations. Historical records may indicate it was here at one time or it may occasionally come down to visit us.
The remaining 50(ish) butterflies have extensive historical records in the valley or are very common in our area.
Acmon Blue
The Acmon Blue has a very clear association with a diverse variety of buckwheats as both host and nectar plants. Yarrow and mustard are occasional treats, as are heliotrope (in the same family as valerian) and wild pea. Approx 99 flower photos analyzed, halfish of which are Acmons on Buckwheats.
American Lady
I decided to only go through 25 of the several hundred pages of photographs. There is no shortage of this butterfly and its preferences were becoming quite clear with these photos. Most of the observations are on non-Willamette Valley native plants in the aster family, along with butterfly bush. Lantana and non-native verbenas are also favorites. Native favorites include aster and milkweed. Approx flower photos analyzed 215.
Anise Swallowtail
The anise swallowtail doesn’t appear to be strongly associated with flower feeding. It will occasionally feed, and when it does it seems to have a preference for dandelionish flowers, butterfly bush, thistle, lantana, verbena. It widely samples a lot of other native and non native flowers. Approx flower photos analyzed 78.
**Arctic Skipper
The arctic skipper seems to have unique preferences for geranium and wild vetch/pea. This species is more likely to be seen higher in the mountains or in the northern range of the Willamette Valley. Approx flower photos analyzed 30.
Boisduval’s Blue
Buckwheat seems to be its favorite nectar plant, but will also go for cinquefoil, Oregon Sunshine, and strawberry occasionally. A few photos of Oregon Sunshine and some type of senecio/groundsel are used. Approx flower photos analyzed 56.
Note: Fender’s Blue Butterfly is a subspecies of Boisduval’s I will write a substack post on the information I can find in the coming weeks.
**Bramble Green Hairstreak
Does not appear to have strong nectar preferences. Approx flower photos analyzed 10, all of them random.
Brown Elfin
This butterfly has a clear love of buckwheat. It will also take from ceanothus, manzanita, mustard. Approx flower photos analyzed 35.
California Sister
Does not drink nectar often, and no strong associations can be gleaned from observations. 4 flower photos analyzed.
California Tortoisheshell
Does not take in much nectar, and does not seem to strongly prefer any flower over others except for the occasional Prunus family. Approx flower photos analyzed 19.
Cedar hairstreak/juniper hairstreak
I decided to go through only 20 pages of photos. Since this is such a widespread species, many flowers are unrecognizable to me. It clearly will take sustenance from many flowers. I noticed a wide variety of milkweeds that it will go for, as well as fleabanes. Senecio/groundsel type flowers are a favorite, buckwheat, yarrow. Approx flower photos analyzed and identified: 127
Clodius Parnassian
The clodius clearly has an association with senecio/groundsel type flowers. In addition, it really likes pearly everlasting, aster, and dogbane. Approx flower photos analyzed 69.
Clouded Sulfur
Has a clear affinity for asters, will take in all manner of aster family plants. Also enjoys the occasional milkweed.
Common Checkered Skipper
I went through 20 pages of photos, then stopped. It is clear that this butterfly has a wide assortment of plants that it gets its nectar from, but true asters were somewhat preferred. Approx flower photos analyzed 122.
**Common/ochre Ringlet
Approx flower photos analyzed 110. Erigeron, Yarrow, Goldenrod were top choices for this butterfly. Possibly chickweed - but I was struggling with identifying the plant.
**Common Roadside Skipper
From the photos, it looks like it has a strong association with blackberry, and I believe most of them were trailing blackberry. It also likes various pea family relatives and verbena. Approx flower photos analyzed 33.
Common Wood Nymph
The most common native plants that it is attracted to in our area are Dogbane, aster, goldenrod, pea family. I am struck by just how attracted this species is to purple flowers. Even more attracted to echinacea and monarda which are not native here, but are native in other parts of the country where the common wood nymph lives. Approx flower photos analyzed 117.
Dun Skipper
Has a wide variety of foods it will accept. Natives are milkweed, dogbane, prunella, erigeron. Approx flower photos analyzed 145.
Eastern Tailed Blue
I went through only 20 pages of photos. This one has a very strong relationship with non-native clovers. Approx flower photos analyzed 76, approx half of which are on non-native clovers. The other photos no clear preferences were observed.
Echo Azure
Ceanothus and buckwheat are the most used commonly seen flowers native to our area. Mustard, manzanita, senecio, and in general yellow composites also used. Approx flower photos analyzed 50
Edith’s Checkerspot
Yarrow, buckwheat and senecio/groundselish flowers are the most commonly used native plants to our area. Approx flower photos analyzed: 40.
Note: Taylor’s Checkerspot is a subspecies of Edith’s. It was presumed extinct in the valley until recently, now considered endangered. I’ll be writing a specific substack on this species soon.
**Field Crescent
This butterfly clearly has a liking to asters and fleabane/erigeron. It also seems to go for yarrow, cinquefoil, grindelia, dogbane, senecio/groundsel, helenium. Approx flower photos analyzed: 113.
Gray Hairstreak
This butterfly sips from a wide range of flowers. The ones native to here: buckwheat, cinquefoil, milkweed, composites/goldentop/senecio. Approx flower photos analyzed 148
**Great Purple Hairstreak
Clearly has an affinity for milkweed. Goldenrod is a second favorite. Otherwise it is seen on a wide range of plants. Approx flower photos analyzed: 54.
Great Spangled Fritilary
This butterfly is listed as a conservation strategy species in the Willamette Valley. It clearly has a love of milkweed of all kinds. It also likes dogbane. Other plants native to areas where this butterfly is also native to: echinacea, monarda, zinnia. Approx photos analyzed: 254.
Green Comma
The Green Comma does not feed extensively at flowers. When it does, it prefers that of Dandelionish. Pearly Everlasting and various Aster species are its native favorites, along with some type of unspecified senecio/groundsel. Approx photos analyzed 42
Hoary Comma
This butterfly has a clear affinity for pearly everlasting, along with yellow composites of several kinds. Approx photos analyzed 62.
Hydaspe Fritilary
This Fritilary has a very strong association with pearly everlasting. It also likes dogbane quite a bit. Senecio/groundsel/arnica/yellow composites are a favorite too. Approx flower photos analyzed: 82.
Johnson’s Hairstreak
Does not feed extensively at flowers and is very uncommon, though it has been seen recently in our area. I couldn’t ascertain any preferences.
Juba Skipper
Yellow composites, including a lot of rabbitbrush, are clearly what this butterfly likes. More local native favorites include pearly everlasting and aster. Approx photos analyzed 75.
Lorquin’s Admiral
There aren’t too many photos of this particular butterfly on flowers, but when it feeds it is most commonly seen on ninebark and Dogbane. 33 photos analyzed.
Margined white
This species appears to have a fondness for geraniums, some presumably native but several non-native. It also likes dandelionish flowers and some daisyish flowers. It likes cardamine, occasionally dogbane, and senecio/groundselish flowers. Approx photos analyzed 63
Milbert’s Tortoiseshell
Particularly likes senecio and other yellow composites in general. Goldenrod, milkweed, pearly everlasting. Approx photos analyzed 165.
Monarch
It is clear it has a wide range of flowers that it likes. The most notable native flowers for our region include its host plant, milkweed, and goldenrod. Approx photos analyzed 190.
Monarch is a conservation strategy species in the Willamette Valley.
**Mormon Metalmark
Seems to have a love of buckwheats in particular. It takes in a few senecio flowers as well.
Mourning Cloak
Mourning Cloaks don’t often nectar, but when they do, they will occasionally take from Milkweed (the clear favorite). 66 approx photos analyzed.
Mylitta Crescent
Sips from a wide assortment of plants, but has a preference for aster family. Aster, Erigeron, pearly everlasting, senecio. Also enjoys milkweed and mustard on occasion.
Orange Sulfur
I went through 20 pages of several hundred pages of photos and got a clear idea that it has a wide variety of flowers that it draws from. However, it is one of the few that is extensively documented on blanketflower. Aster, erigeron, senecio, and milkweed are other favorites. Approx 200 flower photos analyzed.
Oreas Angelwing/Comma
There are no photos of this on flowers. Appears to be a sap feeder along with rotting fruit.
Painted Lady
A widespread species that accepts a wide variety of flowers as nectars. Most of the usual suspects, does not appear to have strong preferences. Approx flower photos analyzed: 48.
Pale Swallowtail
The strongest association for pale swallowtails are dogbane, penstemons (I believe all the ones I saw were native, not hybrid species), mock orange, milkweed, columbine, thistle of course (many of these photos were of non-native thistles) and chokecherry or bittercherry. Approx 102 photos analyzed.
Persius Duskywing
Insufficient data to determine any preferences.
Pine White
Aster, goldenrod, pearly everlasting, senecioish and yarrow are favorites. Approx flower photos analyzed: 104.
Propertius Duskywing
Approx 34 flower photos analyzed, no clear association with any particular flowers.
Purplish Copper
Erigeron/fleabane, pearly everlasting, Senecio/groundsel and goldentop-type flowers are favorites. Approx flower photos analyzed: 155.
Red Admiral
Noted to not drink nectar unless sap is unavailable. It was seen on Milkweed and Dogbane more than once, but was seen drinking from a few other random flowers. Approx flower photos analyzed: 49.
Satyr Angelwing
Approx 18 flower photos analyzed, could not see any clear preferences.
Silver Spotted Skipper
Accepts a wide variety of flowers. Seems to enjoy Monarda more than others, and a slight preference for milkweed as well.
Silvery Blue
This butterfly appears to have a strong preference for nectaring on host plants, most commonly vetches and some thermopsis. It will take in Camas and Bluedicks early in the season. Strawberry and popcorn flowers are slight preferences as well.
Sachem
I’m unclear as to whether this species is considered a non-native migrant on non-native grasses. Regardless I only went through 5 pages of photos, and came away with a clear understanding that this butterfly has a wide range of food preferences in different families - and they are the usual suspects of a lot of common garden flowers. Approx photos analyzed 71
Sarah’s Orangetip
Has a strong preference for Fiddleneck and Mustard. Will also occasionally take in Bluedicks.
Snowberry Checkerspot
Approx 27 flower photos analyzed. Yarrow seems to be its favorite, along with some pearly Everlasting and the occasional allium.
Sonora Skipper
Approx 16 flower photos analyzed. Does not have any clear favorites.
**Tailed Copper
22 photos analyzed. Buckwheat seems to be a slight preference.
Two-banded checkered skipper
17 flower photos analyzed, not many nectar observations. It seems to like dandelionish flowers and was seen on potentilla and senecio more than once.
West Coast Lady
Seems to have a wide variety of plants it likes to get nectar from. Approx photos analyzed 87. No clear preferences.
Western Meadow Fritilary
Seems that valerian is a favorite. Erigeron/fleabane, senecio/grounsel type flowers and oddly it looks like thermopsis was mixed in there a few times too. Approx flower photos analyzed 44.
Western Tailed Blue
This butterfly is not spotted often. It seems to want to nectar most on its host plant (pea family), occasionally taking in strawberry, potentilla, buckwheat, and erigeron. Approx 32 flower photos analyzed.
Western Tiger Swallowtail
By far the most popular native nectar plant is milkweed of various types. Dogbane is second most important, followed by blackberry, mock orange, agastaches, columbine, columbia tiger lily, penstemon of various kinds, red columbine, senecio, and thistle. Approx photos analyzed 250.
Western White
Approx 70 flower photos analyzed. Does not have any strong preferences, and will take in the usual suspects.
Woodland skipper
Clearly this butterfly has an affinity for lavender, which I’ve witnessed in my own garden. Beyond that, it seems to enjoy a wide array of flowers in the daisy family, particularly aster, pearly everlasting, grindelia, erigeron and some kind of senecio/groundsel. It will take in the occasional milkweed and dogbane. Approx photos analyzed 137.
Zerene Fritilary
The zerene fritilary has a clear association with Pearly Everlasting, rabbitbrush, dogbane. Agastache and asters are two more of its favorites, along with senecio/groundsel.
Note: the Valley Silverspot was the subspecies of Zerene that lived in our region, and is now thought to be extinct. In addition the Oregon Silverspot is a subspecies of Zerene. It’s historical range was all along the coast but is now threatened.
**The asterisks are denoting which species are less likely to be seen in the valley, more common in higher elevations. Historical records may indicate it was here at one time or it may occasionally come down to visit us.
Specific Flower Counts:
Apocynaceae family
Dogbane 106
Milkweed 272
Aster Family 2226 (roughly 50%)
Arnica 9
Aster 237
Balsamroot 3
Blanketflower 17
Blue mistflower 20
Coneflower (Unidentified, or, yellow other than rudbeckia ) 7
Coreopsis 16
Cosmo 18
Daisy-ish (oxeye, most likely) 136
Dandelion-ish 269
Echinacea 160
Erigeron/fleabane 132
Goldenrod 89
Grindelia 20
Joe Pye/boneset 44
Helenium 11
Knapweed 50
Liatris 28
Marigold 36
Mule’s ears 3
Oregon Sunshine 9
Pearly everlasting 108
Rabbitbrush 79
Rudbeckia 38
Senecioish 161
Sunflowerish 52
Tansy 11
Thistle 107
Tithonia 25
Yarrow 88
Yellow composite, unidentified 104
Zinnia 139
Borage family
Borage family, unspecified 14
Fiddleneck 13
Heliotrope 11
Mertensia 5
Phacelia 3
Popcornflower 10
Yerba Santa 4
Buckeye trees 13
Buttercup family
Buttercup (mostly creeping) 10
Delphinium 5
Ceanothus 19
Checkermallows 3
Dianthus 16
Fire weed 11
Geranium 28
Honeysuckle family
Abelia 2
Jupiter’s Beard 6
Scabiosa 17
Teasel 7
Valerian 32
Weigela 1
Lily family
Agapanthus 8
Allium, unspecified 16
Blue dicks 7
Brodiaea 7
Columbia lily 6
Camas 7
Chives 3
Mint family
Agastache 25
Catmint 10
Coyote mint 19
Lavender 37
Mint, general unspecified 27
Monarda (mostly purple, very few on the red) 58
Mountain mint
Oregano 14
Rosemary 5
Mustard family
Mustard 55
Raddish 10
Pea family
Clover 151
Lupine 16
Peas, various wild types vetches, vicias, etc 99
Plantain family
Butterfly bush 240
Penstemon 19
Phlox family
Phlox - (mostly creeping, ground cover phlox) 24
Gilia 4
Polygonaceae family
Buckwheat 128
Olive family
Lilac 42
Ribes 3
Rose family
Blackberry 48
Ninebark 7
Potentilla 37
Prunus 27
Strawberry 21
Umbels
Lomatium 5
Mostly unidentified (probably queen annes lace) 19
Vervain family
Lantana 82
Verbena 40
Violet 6
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