I Got Paw Paws!

I've been watching the pawpaw tree (Asimina triloba) for fruit pretty carefully—and hey! I got pawpaws! I didn't really expect to get fruit because this tree is "self-incompatible," meaning that the pollen of one flower cannot fertilize the ovary of another bloom on the same tree. In order to produce the fruit I've been waiting for, the bloom needs pollen from another unrelated pawpaw. Now I have only one tree, and the nearest one I can find is on the campus of the nearby community college, approximately 1,500 feet away.

How can pollen possibly travel that distance? It hitchhikes on a fly. This spring I got photos of what I believe are fruit flies on the blossom of my pawpaw…

but can we expect a 2.5 millimeter fly to travel 457 meters to find another tree's bloom? Well, either a fruit fly has no trouble flying almost 183 thousand times its body length, and has the power to smell a blossom 0.3 miles away, or—more likely—there's a closer pawpaw that the flies aren't telling me about.

I've blogged about my pawpaw tree and its pollinators in May and the how the Zebra Swallowtail uses it as a host play last July. Yes, I'm a little obsessed with it. I'm dreaming about tasting the ripe fruit in the fall, which I'm told tastes like a lemony banana. True, the squirrels will probably get it long before I do, but I can dream can't I?

Pawpaws and Pollinators

With large, tropical-looking leaves, and a dark, mysterious flower, the Pawpaw (Asimina triloba) is the kind of tree Tennessee Williams would have planted next to the magnolias, if he had been into gardening. The blooms look like a dark red bell hanging below the branch. The dark color makes them less than showy than a Flowering Dogwood, but attractive, especially when backlit by the afternoon sun. It’s the classic Missouri bottomland tree, but when I mention that it’s pollinated by flies because the bloom looks like roadkilll—well, it turns people off.

I wrote about Pawpaw’s relationships with butterflies and moths last July. Still, people imagine, as I did, a Pawpaw in bloom, swarming with big hairy flies and a putrid odor wafting on the wind. Nothing could be farther from the truth. I took the photo above on April 20, but when I downloaded it from the camera and the photo filled the screen, I saw the flies for the first time. The flower was about 2 inches across at its widest point. I would have had to wear my reading glasses to see the flies.

Pawpaws don’t make it easy on a pollinator. To bear fruit, the bloom needs pollen from an unrelated Pawpaw. What’s more, process depends on a pollinator that is believed to be inefficient, sloppy, and promiscuous—that is, it’s like to visit many things other than a bloom of a Pawpaw.

Gosh, the flower looks alarmingly fleshy in this extreme crop! Those flies look pretty scary too, but the red eyes in the photo are caused by the flash.

  

Ted MacRae at Beetles in the Bush wrote about Pawpaws last May. In comments,  James Trager, entomologist and restoration biologist at Shaw Nature Reserve, wrote that the tree is likely pollinated by fungus gnats. Fungus gnats are important pollinators, but the critters in my photo don’t have the comparatively long legs I associate with gnats.

I posted my photo on Bug Guide to ask for some ID help.  One person suggested that they could be lesser dung flies. I estimated that the fly was 2 mm long or less—about the right size for dung fly family (Sphaeroceridae).  The Wikipedia article states that dung fly larvae eat fungus or bacteria on rotting vegetation. Another user on Bug Guide suggested that because the blossoms are stinky, they must be some type of carrion fly. That brings us to the next question, what does a Pawpaw blossom smell like? 

I headed out to the tree again and got up close and personal with the flower. It didn’t smell like roadkill, or dung—it had just the faintest odor of yeast. I could only detect the scent when my nose touched the bloom. Of course, yeast is a fungus, so fungus gnats and lots of other decomposers should find the fragrance attractive. But why be shy about the aroma if the plant really wants to be pollinated? 

I have some ideas about that. First, just because the odor is hard for me to detect doesn’t mean that it’s hard for insects to find. Although I had been thinking that there was only one specialized organism that pollinated Pawpaws, I found this statement in a 2001 article in Ecology and Society by Carol Ann Kearns:  "Many species of flies are generalists that visit multiple plant species." There are probably a number of different fly families that offer their pollination services to Pawpaw, though the flies don't seem to get any reward. 

Second, it's possible Pawpaw is a bit conflicted about this whole fruiting process. According to California Rare Fruit Growers, because each bloom has more than one ovary, "a single flower can produce multiple fruits." Add to that this advice to growers resorting to hand pollination, from a 1990 article from 

Kentucky State University Cooperative Extension Program: "

Do not overburden the tree with fruit, as this will stress the tree, resulting in smaller than normal fruit, and may cause limbs to break under excessive weight." Perhaps half-heartedly attracting an inefficient pollinator is Pawpaw's adaptation to it's own heavy fruit.

Fire Pink

Besides having a stunning red flower, Fire Pink (Silene virginica) attracts hummingbirds, and I'm all about that! So I made a number of clumsy attempts to grow it in my garden and always failed, until last year. That's when I decided to get serious about imitating the habitat where I first found it: on a dry, rocky, west-facing hillside in Jefferson County, Missouri.

A glade garden may seem an odd choice in an east-facing, suburban front yard, but that's where I have a slope and the greatest hours of sunlight. I started by removing the Bermuda grass, and some of the dry, clay soil. I replaced it with crushed limestone, and topped that with the rocks. I had to purchase rocks that I could lift, so I looked for ones that could fit together to give the impression of a rock shelf. Then I tamped and pounded till they seemed stable. Once you install an artificial limestone/dolomite ledge, you're pretty well committed, so I really needed a success.

I had a moment of panic when I reread Kurz' description of the typical habitat in Ozark Wildflowers: "wooded slopes in sandstone, chert, or igneous soils." That suggested acid soil, not clay and limestone. As they say though, the plants don't read the books, and the Silene gods smiled on me. My Fire Pink bloomed well last year and returned for an even stronger show this year. Dan Tenaglia's website, MissouriPlants.com, has really great photos of this plant in the wild, and the rocks in his photo look suspiciously like limestone/dolomite.

The stem and calyx of Fire Pink or Catchfly are sticky. John Hilty's website, Illinois Wildflowers (which I talked about in January 2011), says that the purpose of that sticky substance is to discourage ants from "stealing" the nectar. An animal "steals" nectar when it takes nectar without pollinating the flower. Hilty says however that little is known about Fire Pink's pollinators, although is is presumed to be hummingbirds. Even though I've only seen a hummer at the blooms once, I don't have any doubt Silene is a hummingbird plant.

Binoculars for Your Nose

Eastern Witch Hazel is the last tree to bloom in the Midwest. AMcC

I stepped outside on a calm autumn night last week. A fresh, citrus scent was in the air. It reminded me of witch hazel in bloom. That couldn’t be, of course, because my big hybrid witch hazel (Hamamelis x intermedia ‘Arnold Promise”) blooms in February. Then I remembered my other witch hazel tree, a scrawny little guy, completely overshadowed by big brother Arnold and my neighbor’s silver maples. When I bought my home in the 1980s, I knew I wanted a witch hazel tree. I was in love with the one that bloomed by the east wall of the Missouri Botanical Garden in late winter. I knew there was a native variety, but I wasn’t aware of any native plant nurseries in my areas at the time. I ordered Eastern witch hazel (Hamamelis virginiana) from a native plant nursery in the Appalachian Mountains and planted it about the same time as the Asian hybrid. According to Don Kurz’ book, Trees of Missouri, I ended up with a tree that is native to the Ozarks, though not to St. Louis County, Missouri. Two short decades zipped by with only the puniest of blooms, on the slenderest of twigs. Now this fragrance in November…

The next morning I confirmed it; my skinny 12 foot-tree was covered in bloom! The scent is wonderful, but it can be elusive. You can stand right next to a branch in full bloom and not be aware of it. You can be twenty feet away in the dark and know it instantly. Like all scent, it’s hard to describe with words: something like an orange, but lighter. I say full bloom, but that’s “full” by witch hazel standards. The petals are narrow ribbons of yellow, half-inch-long or a bit more. The blooms are often clustered together, without stems. 

With a shovel and a bit of determination, it’s not too hard to remake your perennial border. It’s a little tougher to remedy mistakes with trees and shrubs. If I were to remake the trees in my yard, I’d give my Eastern witch hazel a spot with more light, farther away from it’s winter-blooming relative. Both are covered in golden leaves in fall. One is the last tree of the year to bloom; the other is the first. 

According to John Hilty’s website, “Illinois Wildflowers,” Eastern witch hazel is pollinated by flies, but also a few moths, wasps and beetles. The plant doesn’t need showy petals, streaked with guides to direct butterflies and honey bees to the goodies. It does need scent, and so do I.

Scent may be the most neglected of human senses, but it’s more important than we admit. Grocery store shelves are filled with scented candles, scented oils, scented gel sticks, scented night lights, and scented trash bags. A popular fabric softener comes in 23 different varieties. On their website, you can search by “scent type”: “airy fresh” or “modern exotic.” 100 ml. spray bottles of perfume (3.4 oz) can sell for $100 and up. Gas stations sell air fresheners too. They say “New Car Scent” just flies off the shelf. Fragrance is of the essence in the garden for both humans and pollinators, as I mentioned in “Creatures of the Night.” It might be nice to have a device to amplify our sense of smell. Binoculars for your nose, perhaps?

Bees, Butterflies, and Biodiesel

Monarch Butterfly on Cup Plant bloom AMcC

One of my favorite native plants is Cup Plant, Silphium perfoliatum. My first experience with it was in Hidden Meadow at Girl Scout Camp Cedarledge. My friend Sandy, whose position was “Nature Specialist,” showed me how the large opposite leaves wrap the square stem to form a cup. It had been hot and dry, but when she tipped the tall stalk, water dripped out. Pretty cool! Much later, I read about a couple who got rid of their bird feeders and planted a wildlife garden. I wish I could remember the title of the book, but I do remember that next to their windows, they planted cup plant so that they could enjoy watching the birds use the “natural birdbath.” I resolved to do the same when I got my own home.

Cup plant is a true garden personality. I do sometimes see chickadees and other birds land on the large leaf and dip into the “cup” for a drink. Perhaps they also capture insects in the water. The leaf is pointed, with a jagged edge and rough as sand paper. The stem is thick, smooth, straight, and square, giving it another common name, “Carpenter’s Weed” (Kurz, Ozark Wildflowers, 121). If you were to design a garden plant that breaks all the rules of garden plant developers and hybridizers, you’d come up with Cup Plant. There’s nothing dainty about it. Now you know why I like it!

Cup Plant leaves in June AMcC

By early August, many of my plants are 8 feet tall. Plants that don’t receive as much light and water are smaller. Towering plants with large leaves filled with rainwater sometimes tip over during a storm. If you have a good spot for Cup Plants, plan on staking them up in early summer, and use a really stout stake.

Cup plant blooms are always in demand with bees of all sorts, especially bumblebees. It’s worth remembering that native bees such as bumble bees are much less likely to sting than honeybees, but if you’re concerned, don’t plant it near the door or walkway. I welcome bees and other pollinators, but I found out my mail carrier didn’t. This perennial does spread from the root, so I could afford to thin the herd. Once I removed a plant or two and staked the others up away from the box, he started delivering my junk mail again.

Leaves form a cup as they enclose the stem. AMcC

The blooms of Cup Plant are a bit more than 3 inches across. Like other members of the Aster family, they provide the perfect landing platform for butterflies. When they’re in bloom, I frequently see 4 different butterfly species in the yard at a time. Today’s Cup Plant list: Monarch, Painted Lady, Fiery Skipper, and Checkered White butterfly. Bumblebees, carpenter bees (known as “long-tongued” bees) and butterflies are the most important pollinators for Cup Plant. When it goes to seed, American Goldfinches, House Finches, and (on rare occasions) Pine Siskins will visit.

Butterflies and Moths of Missouri, by J Richard and Joan E. Heizman (1987) mentions that the caterpillar of a moth, Eucosma giganteana (no common name), bores into the root of Silphium. With its wings closed, E. giganteana looks a lot like a small bird dropping—a great strategy for avoiding hungry birds. With a little research, I kicked up this story by P. J. Johnson: In South Dakota, Cup plant is being studied as a possible source of renewable energy! It’s possible that Cup Plant will be used to produce biodiesel fuel or plastics. If it is to be grown as a biomass crop however, scientists need to know about the possible impact of E. giganteana on the crop, especially since Cup Plant is its one and only host or larval food plant. Their studies found the larva in the flower heads, leaves and stems, but not in the root. I did find a caterpillar on one of my plants, but it looked nothing like the larva pictured in Johnson’s article. Apparently, E. giganteana is very uncommon, but I’m still going to examine bird droppings a little more closely.

Of Cabbages and Checkered Whites

Female Checkered White butterfly on cup plant
as a native bee takes aim! AMcC

August is an exciting time in a wildlife garden. My yellow composites are beginning to bloom—cup plant, prairie dock, golden glow, woodland sunflower, and brown-eyed Susan. Goldfinches add to the yellow garden as they harvest purple coneflower seeds for their nestlings. The males sing almost as much and as loudly as robins in May. Pollinators of every kind are busy all day long. All these species are on schedule, and then a surprise: a Checkered White butterfly! Checkered Whites are not rare, but they are new to my “yard list.”

You might not think a member of the family of “Whites” or Pierids would be eye-catching, but I think the female’s pattern is really appealing. I was thrilled with the new species, but I didn’t realize how uncommon this sighting was till I talked to my friend, Yvonne Homeyer. Yvonne writes the butterfly report for our local chapter of North American Butterfly Association and serves on NABA’s board of Directors. She pointed out that this year Checkered Whites have been seen in just a few gardens and not reported at all in natural areas.

I did a bit of checking on the abundance of Checkered Whites. In Brock & Kaufman’s Butterflies of North America, the map indicates that they are uncommon in my area (St. Louis County, MO). Glassberg’s Butterflies through Binoculars; The East says, “Abundance of this species greatly fluctuates.” Wagner, in Caterpillars of Eastern North America, says, “This species has declined precipitously over the east in my lifetime.”

Why this should be is unknown. Checkered White caterpillars can eat just about anything in the mustard/cabbage family (Brassicaceae), which includes plenty of native and non-native weeds as well as garden vegetables. I didn’t think I had any of the host plants in my yard, till I checked Denison’s Missouri Wildflowers. I have a small area of toothwort (Carmdamine), which I didn’t realize was in the mustard family. A plant they seem to use quite heavily is pepper grass, which is abundant in the nearby city property and college campus. Every yard seems to have another brassica, the invasive, non-native hairy bittercress.

I spent about 3 days trying to get photos. Monday, I saw a male Checkered White, but it had disappeared by the time I got my camera. Tuesday was a scorcher, 100° with high humidity. I ran out of the air-conditioned house with the camera as soon as I spotted it through the window. This butterfly was a very cooperative female, but the condensation on my lens made the images useless. Amazingly, I saw another female Checkered White on Wednesday and was able to get some decent shots, in spite of the fact that it didn’t linger long at a blossom. It’s really nice to study the photos later and see native bees and an Ailanthus Webworm moth in the frame.

I recognize the female butterfly by the checkered markings, especially on the hind wing. But if I were a  Checkered White butterfly, according to the University of Florida’s Institute of Food and Agricultural Sciences, I’d look for a different “UV reflectivity.” I guess that would be pretty attractive too.

Seeing such a beautiful, pale butterfly kind of makes up for the wounds of reading that its preferred habitat includes “dry weedy areas” (Milleman, Mizzel, Jones on “Web Only Display of Miscellaneous Local Insects”) and—even worse—“disturbed open areas…(and) abandoned railway tracks” (Glassberg, 52). I don’t like to think of my front yard as “disturbed,” but it is interesting that I have only seen it in the front among cup plants and a number of species adapted to dry glades. So far, it has ignored my backyard of tall phlox, butterfly bush, and swamp milkweed.

Female Checkered White Butterfly shares Cup Plant
with native bees and Ailanthus Webworm moth AMcC

“The time has come,” the Walrus said,

“To talk of many things:

 Of shoes—and ships—and sealing wax—

 Of cabbages—and kings.”

Lewis Carroll 

Things you didn’t know you didn’t know

One of the great things about learning about nature is meeting really interesting people. I  knew the name Ted MacRae from our nature study group and found his blog, Beetles in the Bush. It challenged me to learn about creatures I had never even noticed before, especially those beautiful tiger beetles! It’s always great to learn things you didn’t know that you didn’t know. Later I met Ted in person and found that he was not only a great  entomologist and writer, but also a friend. His invitation to write a post on Beetles in the Bush was intriguing. I enjoyed writing “Dogbane for Dinner” so much, I started “Gardening with Binoculars.” Thanks, Ted!

Those Ever-Lovin' Vines!

Pop used to call them “Those ever-lovin’ vines!” and it was clear he was not in love with them. I don’t know any gardeners that are. I’m talking about those vines that spring from nowhere just to deface your Japanese maple. Edgar Denison calls it Angle-Pod, others use the common names Climbing Milkweed, Bluevine, Honeyvine, or Sandvine. Or Everlovinvine.

This plant is a stalker—literally. The stem twines slyly around the stalk of your treasured perennial. You won’t even notice it till it starts to bloom. By then it’s tied a dozen plants into an impenetrable tangle, snapping stems under the weight of the hitchhiker and the next rain. Its blooms are insignificant and white, but put out strong perfume, calling bees and flies to pollinator duty. The fragrance is sweet to humans too, but for my money, it’s too sweet.

Removing Cynanchum laeve requires delicacy and restraint. The vine twines with a counter-clockwise motion, so to remove, you must carefully twist it in a clockwise direction. The temptation to pull is usually too much for me, and that yanks off the flowers I’m trying to save. A better strategy is to use scissors to clip the vine every few inches, then pick off each piece. The root is deep. It looks like long, thin, white carrot. If you choose to leave the root, the vine will sprout right back. You understand, of course, that removing the root will pretty much destroy that section of your garden. The best plan is to let the vine grow long enough so that you can safely hit it with herbicide, leaving the rest of the garden untouched. Good luck with that.

When all else fails, comfort yourself with the knowledge that Monarch butterflies and their caterpillars love this plant. I’ve seen caterpillars on it a number of times. Sometimes I just hook it with the side-view mirror as I back out of my driveway and drive around town with a vine and black-eyed Susan dangling from my passenger side. Works for me!