Some Uncommon Things About Common Milkweed

Common Milkweed, Asclepias syriaca, blooming on June 30, 2021, at Crow Hassan Park Reserve in Minnesota.

 

At times reviled as a nuisance of farm fields and pastures, Common Milkweed (Asclepias syriaca) has gained new respect as a plant that supports Monarch Butterfly larvae. That’s just part of the story, though. Here are a few things about milkweed that get less attention.

• The plant’s scientific name, Asclepias syriaca, is centuries old. It was given by Carl Linneaus, the Swedish botanist who in the 1700s developed the binomial system of nomenclature. That's the system that gives plants and other living things two names: a generic name – Asclepias, in this case – and a specific name, also called a specific epithet –syriaca for Common Milkweed.

• Linneaus is said to have been so impressed by the many medicinal uses of common milkweed that he named the plant after Asklepios, the Greek god of medicine. The specific epithet, syriaca, is from Linneaus’ mistaken belief that the plant came from Syria.  

• Syria is a long way from where common milkweed is naturally found. The plant is native to the Eastern and Great Plains regions of the U.S. and adjacent provinces of Canada. Like many plants, however, common milkweed has found its way overseas. It is now also found in southern and central Europe, where it invades grasslands and farm fields (1).

• One reason the plant isn’t always welcome is because it’s toxic to many animals, including humans. Like other milkweeds, the plant’s white latex contains cardiac glycosides, compounds that affect the function of the heart. Depending on the amount consumed, milkweed latex can cause symptoms ranging from nausea and vomiting to slowed heart rate, coma and even death (2).

• Some animals can eat milkweed safely. Milkweed bugs, for example, can isolate the cardiac glycosides they consume while they munch on leaves and other plant parts. The insects themselves then become toxic, which makes them unpalatable to predators. Their bright colors warn potential diners that eating them would be a mistake (3).

• Evidently, milkweed bugs have a lot of company. According to the U.S. Forest Service, common milkweed is a “mega food market” that feeds more than 450 kinds of insects. Some, like milkweed bugs, are destructive, but others merely sip the plant’s nectar or suck out its sap (4).

• Medicinal uses of common milkweed have waned, but not long ago, the plant saved lives in a different way. During World War II, milkweed pods were collected for the silks attached to their seeds. The buoyant, waterproof strands, called milkweed floss, were used to stuff life preservers when kapok, another plant fiber used for that purpose, could not be obtained from Indonesia.

• Milkweed floss was in such demand that school children were paid to gather the pods. The going rate was15 to 20 cents per onion bag or gunny sack filled with pods. Two bags provided enough floss to make one life preserver.

• Although it’s hard to imagine milkweed floss making much difference in the effort, the plant was abundant enough to have made an estimated 1.2 million life preservers. Milkweed was so valuable that the U.S. government considered it a “wartime strategic material” (5).

• After the war, common milkweed lost its status and was once again considered a weed. From reviled to revered and back again, shifting fortunes seem to define milkweed’s history.

References

(1) Asclepias syriaca (common milkweed). CABI Invasive Species Compendium. Viewed 6/30/21 at https://www.cabi.org/isc/datasheet/7249.

(2) Milkweed Plant Can Cause Serious Poisoning. Poison Control, National Capital Poison Center. Viewed on 6/30/2021 at https://www.poison.org/articles/milkweed-can-cause-serious-poisoning-204.

(3) Common Milkweed Insects. Susan Mahr, University of Wisconsin-Madison. Wisconsin Horticulture, Division of Extension. Viewed on 6/30/21 at https://hort.extension.wisc.edu/articles/common-milkweed-insects/.

(4) Plant of the week: Common milkweed (Asclepias syriaca).  David Taylor. U.S. Forest Service, USDA. Viewed on 6/30/2021 at Common Milkweed (fs.fed.us).

(5) A weed goes to war, and Michigan provides the ammunition. Gerald Wykes, from Michigan History magazine. Posted February 4, 2014, and updated January 20, 2019, on MLive. Viewed on 6/30/2021 at https://www.mlive.com/news/2014/02/a_weed_goes_to_war_and_michiga.html. 

Antsy Plants

From left: Wild Ginger, Nodding Trillium, and Bloodroot in early spring. 

Wild Ginger, Trillium and Bloodroot are done flowering, but that's not the end of their efforts. Now they must disseminate their seeds, and each has arrived at the same, six-legged solution to accomplish that task: Ants.

Myrmecochory (often pronounced MUR-mecco cor-ee), the dispersal of seeds by ants, is a convenient invention. Ants are found all over the world, from the tropics to the Arctic, so they are a ready resource. Similarly, plants that employ ants for seed dispersal live in diverse habitats, including the tropical rainforests of Latin America, the dry shrub communities of South Africa and Australia, and the eastern deciduous forests of Europe and the U.S. (1). Myrmecochory is thought to have developed independently more than 100 times, with more than 11,000 species of plants relying on these insects to spread their seeds (2).

That nature converged on the same solution in different, and distant, plants suggests that it works. Like any method of seed dispersal, though, myrmecochory has a cost. It demands adaptations, and in one group of ant-dispersed plants, that adaptation is in the form of a bribe.

To lure ants, myrmecochores attach small, fatty bodies called elaiosomes (e-lay-o-somes) to their seeds or fruits. Depending on the species, these mini nutritional packets are clear, white, brown, or other colors and shaped like worms, flags or amorphous dollops. Some may emit an odor like rotting insect carcasses, a trick to attract ants to take the seeds back to their nest, remove and feed the elaiosomes to the colony, and leave the seeds to germinate (1).

From left: Wild Ginger, Nodding Trillium, and Bloodroot seeds with their elaiosomes.

Both plants and ants are thought to benefit from this relationship. Plants benefit by reducing competition for light and nutrients between parent plants and their offspring. Moving seeds away from the parent plant also lessens the risk of local extinction: If one part of a population dies, another, more distant, part may survive. Another potential benefit is reduced seed predation. Perhaps better than any other animal, ants can disperse a cache of seeds meters away from the parent before mice, birds or other seed eaters find them.

One more potential benefit is improved seed germination. Seeds discarded in or near ant nests may end up in refuse piles, nutrient-rich microenvironments that can aid germination and seedling growth. The medium in ant nests may also retain more water or be better aerated, another potential aid to germination and growth. 

Ants benefit from myrmecochory, too, and it's likely they're adapted to the interaction. Not all species of ants forage for seeds that have elaiosomes, but those that do may have some yet-unknown characteristics that lead them to that behavior. Widespread though it is, this mutually beneficial relationship still has some secrets to share.

Myrmecochores of Minnesota

The ant-dispersed plants in this region tend to be early-blooming herbs of deciduous forests. Here are a few, based on personal observation or mention in references. 

Bloodroot (Sanguinaria canadensis)

Nodding Trillium (Trillium cernuum)

Wild Ginger (Asarum canadense)

Yellow Violet (Viola pubescens)

Spring Beauty (Claytonia virginica)

White Trout Lily (Erythronium albidum)

References

(1)    Handel, S.N., and Beattie, A.J. (1990). Seed dispersal by ants. Scientific American 263 (2): 76-83B.

(2)    Lengyel, S., Gove, A.D., Latimer, A. M., et al. (2010). Convergent evolution of seed dispersal by ants, and phylogeny and biogeography in flowering plants: A global survey. Perspectives in Plant Ecology, Evolution and Systematics 12: 43-55.

Plant Profile: Wild Geranium

Wild geranium (Geranium maculatum) is a native, herbaceous perennial of open woods and woodland edges. It begins blooming in May, about the same time as Trillium, with loose clusters of pink to lavender flowers at the ends of hairy stems. The plant is also called wild cranesbill or storksbill for the long, beak-like capsules produced after flowering.

In the flower on the left, the inner ring of anthers is releasing pollen.

The stigma is not yet mature. On the right, the anthers are past maturity

and the curled, five-parted stigma accepts pollen.

The anthers in a flower mature first – an outer ring and then an inner ring – followed by the stigma of the pistil, a sequence that favors cross-pollination (1). A variety of bees, flies and beetles visit the flowers for nectar and pollen, guided, or maybe lured, by the lines on the flowers’ petals. Larvae of several insects also feed on the plant (1).

Collecting seeds from wild geranium can be tricky. As a capsule matures and dries, each of its five parts separates from the central column and curls upward, flinging the seed from the oval chamber at the base. To catch the seeds, it's best to collect the capsules when they just begins to change color. Put them in a closed paper bag to dry and release its seeds. 

The seeds need a period of cold, moist conditions before they will germinate, so either sow them outdoors in fall or treat them artificially (2). Instructions are available from Prairie Moon Nursery, prairiemoon.com.

Left: A nymph of the Fork-tailed Bush Katydid (Scuddaria furcata) visits a Wild Geranium flower. Right: A Thick-headed Fly (Myopa species) sips nectar.

Wild geranium also reproduces vegetatively. Thick rhizomes produce patches of plants that can be divided, ideally in spring or fall. Cut the rhizomes where they make right angles (2). Of course, don’t harvest rhizomes on public land or on private land without permission.

Immature (left) and post-mature (right) capsules of Wild 

Geranium. Seeds have already been released from the 

capsules on the right.

A few plants have leaves that look like wild geranium. Sanicles, also called black snakeroots (Sanicula species), grow in a similar habitat but have alternate leaves on the stem, in contrast to the opposite leaves  of wild geranium. Also unlike wild geranium, Sanicle stems and leaves have no hairs (5). Canada anemone (Anemone canadensis), usually found in wetter habitats than wild geranium, has leaves with sharper teeth (3). Like wild geranium, its stems are hairy, but the hairs are spreading or ascending. In contrast, the hairs on the stems of wild geranium point downward (5)

 

Wild Geranium spreads vegetatively by rhizomes. The largest

one is about as thick as a thumb.

References

(1)    Pollinators of Native Plants, by Heather Holm. Pollination Press, Minnetonka, MN. 2014.

(2)    Wild Geranium, Geranium maculatum. Wisconsin Horticulture, Division of Extension. University of Wisconsin-Madison. Website accessed May 31, 2021. https://hort.extension.wisc.edu/articles/wild-geranium-geranium-maculatum/

(3)    Geranium maculatum (Wild Geranium). Minnesota Wildflowers. Website accessed May 31, 2021. https://www.minnesotawildflowers.info/flower/wild-geranium

(4)    USDA, NRCS. 2021. The PLANTS Database (http://plants.sc.egov.usda.gov, 05/28/2021). National Plant Data Team, Greensboro, NC USA.

(5)    Flora of the Great Plains, by the Great Plains Flora Association. University Press of Kansas, Lawrence. 1986. 

The Pretty Problem of Siberian Squill

Siberian Squill (Scilla siberica) is an introduced plant that blooms in early spring. Leaves are basal, up to six inches long and 1/2 inch wide. Flowers are blue on leafless stalks. This ephemeral plant dies back in late spring. 

Siberian squill is a beautiful, eye-catching plant. Its bright blue flowers are among the first to bloom in spring, providing a pop of early color in gardens, lawns and woodlands. To many who are winter-weary, it's a welcome sight.

Lately, though, the plant is getting attention for a different reason. The same qualities that have long made Ssquill popular – its profusion of flowers, its tendency to spread into masses, its easy propagation – have also raised suspicions that it can be invasive. In some places, squill has jumped the garden border or the naturalized planting to grow where it wasn’t intended. That includes deciduous forests, where there is rising concern that it can displace native woodland plants.

It has taken a long time, and some long-distance travel, to get here. Squill is thought to have arrived in the United States in the late 1700s, when it was imported from its native range in southwest Russia and the Caucuses [1].  Promoted as an ornamental, it reached the Midwest by the mid-1900s. The first record of squill in the Wisconsin State Herbarium [2] is a plant collected in 1955 from Hortonville, in eastern Wisconsin. Later herbarium records find it at Point Beach State Forest near Manitowoc in 1964, the campus of UW-Oshkosh in 1966, and Turville Woods, west of Milwaukee, in 1975.

Squill reached Minnesota sometime later. The garden census for the Eloise Butler Wildflower Garden has counted squill among its numbers since 1985 [3]. The earliest herbarium records from the Minnesota Biodiversity Atlas [4] are dated 1997, when squill was found in Forestville State Park, and 1999, when it was found in Frontenac State Park, both in southeast Minnesota. Today squill is found throughout much of the state.

Judging from records of its distribution, squill can live quite well outside tended plantings. Freed of any apparent constraints, it can reproduce quickly by bulbs and seeds to form potentially large populations. A sample of EDDMapS reports [5] gives some idea of its ability to spread: 7 square feet of cover in a Rochester park; 800 square feet in a park in Maple Grove; an acre – about 43,000 square feet – in the Roberts Bird Sanctuary in Minneapolis, where squill escaped from a garden into an adjacent woodland reserve.

According to these reports, not all wild populations are (yet) large and dense, but there are more clues this can happen. In fact, some people want it to happen. For example, many gardening websites and advertisements picture broad expanses of squill, wide carpets of blue below an overstory of handsome trees. Far from being a red flag, squill’s habit of spreading is viewed as positive. If the pictures don't say it, the words that accompany them do: “Great naturalizer,” proclaims one advertisement. “Best when planted in large drifts,” advises another. One more takes that advice a step further: “Mass in sweeping drifts in woodland, wild or naturalized areas.”

The fear, again, is that sweeping drifts of squill could broom other plants out of existence. Several native spring wildflowers – bloodroot, wild ginger, Trillium, Hepatica, spring beauty, and others – share a similar woodland habitat and phenology, and they may be unable to compete with an aggressive introduction like squill. Proof of harm needs formal research, but until any such studies are complete, informal studies, reports, and observations are raising concerns.

Suspicions are now great enough that leaders in the gardening world are urging caution. The University of Minnesota Extension Service [6] warns that although squill is beautiful, it may be harmful. “Because of its rapid spread and condition tolerance,” they write, “this non-native species has the potential to become an invasive plant.”

At the Minnesota Landscape Arboretum, managing squill has become a struggle. Gardeners there are frustrated by the difficulty of establishing other plants where squill has spread. One gardener tried digging out squill and planting wild ginger. Unfortunately, two years later squill had rebounded and the wild ginger was all but gone [9].

The Southeast Wisconsin Invasive Species Consortium [7] is also wary. Calling squill “a classic case of gardening gone awry,” the group is alert to the probability of trouble. Citing the plant’s cold hardiness and unpalatability to deer and other herbivores, they lament the consequences of its popularity: “Sadly, the same traits that make it attractive as a garden plant . . . are also what make it invasive.”

 

Understandably, fans of squill find this hard to accept. A lively debate on the Minnesota Wildflowers website includes defenders who like the plant for its beauty, its role as a harbinger of spring, and its sentimental value. Some assert that the plant is well-behaved and is a food source for pollinators. Others want proof that squill displaces native plants.

 

The debate goes to the heart of invasive species biology. Many plants are introduced because, like squill, they're beautiful. People plant them because they admire them. Most of these species cause no harm to natural areas. Marigolds, petunias and impatiens, for example, usually stay put. A few introduced species, though, have it in them to spread. They might limp along for a while, but eventually they gain enough of a toe hold to dominate a landscape, whether it’s a garden, a yard or a natural area. 

Increasingly, squill appears to be one of those runaway species. Some gardeners and natural area stewards have spent years trying to remove squill from garden plots, lawns and woodlands, and their frustration is clear. So are their warnings. They advise removing squill when its populations are small and easier to take out. Better yet, they say, avoid the problem by not planting it at all. 

Proof of harm to native plants and pollinators will take time to complete. If studies confirm that squill is invasive, it will be years before that evidence is published. In the meantime, it's clear from a growing number of observations that squill as an emerging concern. As one gardener at the Arboretum put it, “It’s beautiful, but it’s very invasive. When it naturalizes too much, it’s difficult to get rid of.” [8]

 

Squill is indeed beautiful. This unique plant reminds us of spring and perhaps of those who planted the bulbs with good intentions of creating a pleasing landscape. However, if we’re on the cusp of recognizing that squill can be harmful, now is the time to act. In some places, at least, this pretty plant has become a big problem.

 

Squill Removal and Look-Alikes

Removing Squill can be a tough job, especially if it’s growing in masses. For tips, scroll through the discussion on Minnesota Wildflowers and see the advice from the University of Minnesota Extension Service [6].

 

Squill is easiest to recognize when it’s flowering, but it has some look-alikes.

 

Harebell (Campanula rotundifolia) has bell-shaped, purple flowers on leafy stems reaching 20 inches tall. Typically, it grows in dry, open places. It blooms in summer.

 

Blue-eyed Grass (Sisyrinchium species) has grass-like leaves and dark to pale purple flowers with yellow centers and yellow anthers. Squill has blue anthers. Three species grow in Minnesota, all in sun. They bloom from May to July.

 

Like Squill, Spring Beauty (Claytonia virginica) is a woodland spring ephemeral. It blooms a little later than Squill and has pink-veined flowers. Flowering stems bear long, narrow leaves.

From left: Spring Beauty, Harebell, and Mountain Blue-eyed Grass, Sisyrinchium montanum.
Harebell photo copyright 2008 Katy Chayka. Blue-eyed Grass photo copyright 2012 Peter Dzuik. Both photos are from Minnesota Wildflowers.

 

 

References

[1] Flora of North America. Scilla siberica. Website accessed May 2021.

 

[2] Consortium of Midwest Herbaria, midwestherbaria.org. Accessed May 2021.

 

[3] The Friends of the Eloise Butler Wildflower Garden. Blue Squill, by G.D. Bebeau. 2015. Accessed May 2021.

 

[4] Minnesota Biodiversity Atlas. University of Minnesota Bell Museum. Accessed May 2021.

 

[5] EDDMapS. 2021. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Available online at http://www.eddmaps.org; last accessed May 7, 2021.

 

[6] University of Minnesota Extension Service. Squill, by Angela Gupta, Amy Rager and Megan Weber. Reviewed 2021.

 

[7] Southeastern Wisconsin Invasive Species Consortium, Inc. (SEWISC).  Siberian Squill. Website accessed May 2021.

 

[8] Pretty, but aggressive squill, by Erin Buchholz. Nature Notes. News from the Minnesota Landscape Arboretum. May 13, 2020.

 

 

 

 

Bloodroot's Bet

This herbaceous perennial is among the first to bloom on the deciduous forest floor. It's also among the hardiest.

Bloodroot, Sanguinaria canadensis, in early April 2021.

Every year, bloodroot throws the dice. It blooms surprisingly early, risking the return of winter weather to grow and flower when light intensity is highest on the deciduous forest floor. Its way of surviving in shade is to mostly avoid it, and thanks to several adaptations to cope with the uncertain conditions of early spring, it has succeeded.

Sometime in late March or early April, single basal leaves spear through the leaf litter, wrapped around and protecting flower stalks bearing one, delicate bud. On dry, sunny days, the flowers open like bowls, each a brilliant display of eight or more petals around a mass of orange-yellow stamens and a central pistil.

Little else is blooming at the time, so bloodroot doesn’t have much competition for the few pollinators that are active in early spring. Although bloodroot has no nectar, insects nevertheless circle over the flowers in search of a sugary sip.  A few will land inside, and over the course of a few days, they will find that Bloodroot’s offerings change.

When a flower first opens, only the stigma is mature. The anthers need another day or two before they’re ready to release any significant amount of pollen. Although visiting insects won’t find much pollen to gather from a young flower, they can deliver what they collected from an older one. In rapid succession, the stigma receives the pollen, the eggs are fertilized, and seeds begin to develop. Such cross-pollination has the advantage of mixing genes from different plants, creating new combinations that might improve offspring survival.

Self-pollination isn’t likely to occur at this stage, in part because the anthers aren’t mature but also because the stamens initially bend away from the pistil. By day three in a flower’s life, however, the anthers are fully developed and the stamens change their position. Instead of bending away from the pistil, they bend toward it, increasing the odds that the flower will fertilize itself.

Left: In recently-opened flowers, the stamens and immature anthers bend away from the pistil.
Right: In an older flower (three days or so), the stamens bend toward and even arch over the pistil.

In a sense, this is bloodroot’s life insurance policy. If cross-pollination doesn’t happen – say in a stretch of cold, rainy or snowy weather that limits pollinator activity – self-pollination is a fallback. The resulting seeds will produce offspring much like the parent, but at least there will be seeds, tiny propagules that can be disseminated to expand the population.

Whatever ate these Bloodroot leaves might not have
enjoyed them for long. Bloodroot sap contains several
alkaloids, bitter molecules that can be harmful.

Of course, insects aren’t the only animals looking for food in early spring. Hungry herbivores are also on the prowl, and bloodroot provides some tempting, tender shoots. One chomp and bloodroot could lose its annual opportunity to grow and reproduce. The “blood” of bloodroot tends to discourage that activity, however. It contains several alkaloids, molecules that are distasteful if not harmful to animals that eat them. Alkaloids are most concentrated in the roots, but they are found in all parts of the plant, including the leaves and petioles. A mouthful of the bitter greens could be enough to put an herbivore off bloodroot for a long time.

It’s a gamble to grow early, but bloodroot has adapted to the risk. The plant's fragile appearance belies a durability born of countless generations on the forest floor. Through genetic trial and error, the dice came to be loaded in its favor.     

References

Hayden, W.J. (2005). Bloodroot pollination: Bet-hedging in uncertain times. Bulletin of the Virginia Native Plant Society 24(1): 5+

Matsuura, H., & Fett-Neto, A. (2015). Plant Alkaloids: Main Features, Toxicity, and Mechanisms of Action.

Schemske, D.W., Willlson, M.F., Melampy, M.N. et al. (1978). Flowering ecology of some spring woodland herbs. Ecology 59 (2): 351-366.

Hopeful News About Emerald Ash Borer

 “Attack fungi” could help manage this destructive insect.

University of Minnesota researchers recently discovered insect-attacking fungi in the larval galleries of emerald ash borer. Their finding offers hope that the fungi could help manage this destructive pest.

Emerald ash borer (EAB) is an introduced beetle that kills all species of ash trees. It has been present in the U.S. since at least 2002 and in Minnesota since at least 2009. Even with a federal quarantine (now removed), the insect spread rapidly. According to the USDA, its range now covers most of the eastern U.S. and the Midwest, with isolated infestations as far west as Colorado.

The larvae of EAB cause the bulk of the damage. After eggs hatch, the larvae bore into the inner bark, the area that includes the water- and sap-conducting cells of the xylem and phloem. Their galleries of serpentine tunnels interfere with the flow of needed resources and kill trees in 2-4 years. Hundreds of millions of trees have succumbed to the insect.

Hope for managing EAB rests in part on biocontrols, organisms that prey on eggs, larvae or adults and so reduce their numbers. Three parasitoid wasps have been released in Minnesota as potential biocontrols. More information about that program is available here.

New biocontrols could emerge from recent research by the Minnesota Invasive Terrestrial Plants and Pests Center (MITPPC). In their study published in Fungal Biology, U of M researchers sampled affected trees from Rochester to Duluth and isolated the fungi associated with EAB larval galleries. They identified many types of fungi, including some that are entomopathogenic – fungi that attack insects.

One fungus they identified, Beauveria bassiana, has already been studied for EAB control. The other entomopathogenic fungi they found also need research to see if they, too, could be used to manage the insect.

This good news comes as EAB continues to spread in Minnesota. Since the November 2020 post about EAB, the insect has been confirmed in two more counties, Cottonwood and Blue Earth in southwest Minnesota. The state’s Department of Agriculture maintains a quarantine boundary that now includes 27 affected counties. 

Quaking Aspen Breaks the Ice

 

If you’re eager to see something in bloom, look for quaking aspen (Populus tremuloides). In southern Minnesota, the tree’s flower buds broke in early March and the flowers are almost mature. Don’t expect to see anything showy, however. Early bloomers like quaking aspen tend to be wind pollinated. There aren’t many insects around yet, so they don’t produce large flowers with colorful petals. Instead, quaking aspen produces dozens of tiny flowers on small spikes called catkins.

This is a lengthwise section through a catkin of male flowers. 

Each flower is just a few millimeters wide, composed of a light 

yellow cup, a brown bract with finger-like lobes and hairs, and

stamens. The red "bumps" are developing anthers.

This photo was taken on March 22, 2021.

The only flower parts you might see, if you look closely, are stamens or pistils. Individual trees usually bear only one kind of flower. In other words, trees are either male (pollen-producing) or female (seed-producing). Both male and female trees flower before leaves emerge, timing the wind-driven spread of pollen when there is the least interference.

You might also notice that all or most of the trees in a stand of quaking aspen bloom at the same time. That’s likely because they’re clones. Quaking aspen reproduces vigorously by root suckers, with young plants emerging amid or around a stand of older trees. All individuals in a clone are connected by a common root system and are genetically identical. In a sense, they are one being. 

The stand pictured here, found in western Hennepin County, covers about 2,000 square feet. Most of the trees in the stand bloom at the same time, so they probably belong to the same clone. In other words, that’s one organism covering 2,000 square feet. That’s big, but it’s far from the biggest clone of quaking aspen. A stand in Fishlake National Forest in central Utah, called Pando (Latin for “I spread”), comprises more than 40,000 individuals, all male, together covering 106 acres and weighing an estimated 13 million pounds. Pando was once the largest known organism on Earth, and one of the oldest. Although its exact age is uncertain, the stand is thought to have originated at the end of the last glacial period, about 11,000 years ago.

Unfortunately, Pando may be declining. Scientists have noticed that the stand is producing fewer young trees. Grazing and browsing of root suckers is one possible reason, but diseases, insects and lack of disturbance, which favors vegetative reproduction, may also be causes. Efforts are underway to understand why the stand isn’t regenerating and to slow or prevent its further decline.

Far from Utah, in this small stand of quaking aspen, female trees will soon be pollinated and release their cottony seeds. Like the pollen, the seeds are carried by wind, and in a month or so there will be a blizzard of them. If they happen to land where soil is moist – even for just a few hours – they will germinate and an infant stand may be born. It’s a chancy way of reproducing, but even Pando started this way. Big clones from little aspen seeds grow.

References

The Diminishing Pando Clone: History and Forest Management
https://history.utah.gov/the-diminishing-pando-clone-history-and-forest-management/
 
Pando – (I Spread)
https://www.fs.usda.gov/detail/fishlake/home/?cid=STELPRDB5393641
 
Smith. W.R. 2008. Trees and Shrubs of Minnesota. Minnesota Department of Natural Resources. University of Minnesota Press, Minneapolis.