Beavers and Water Lilies – An Introduction to Zoochory

Beavers are classic examples of ecosystem engineers. It is difficult to think of an animal – apart from humans – whose day-to-day activities have more impact on the landscape than beavers. Their dam building activities create wetlands that are used by numerous other species, and their selective harvesting of preferred trees affects species composition in riparian areas. And that’s just the start. Their extensive evolutionary history and once widespread distribution has made them major players in the landscape for millions of years.

Today, the beaver family (Castoridae) consists of just two extant species: Castor fiber (native to Eurasia) and Castor canadensis (native to North America). Both species were hunted by humans to the brink of extinction but, thanks to conservation efforts, enjoy stable populations despite having been eliminated from much of their historical ranges. Before the arrival of Europeans, North American beavers are estimated to have been anywhere from 60 million to 400 million strong. Extensive trapping reduced the population to less than half a million. Today, 10 million or more make their homes in rivers, streams, and wetlands across the continent.

North American beaver (Castor canadensis) - photo credit: wikimedia commons

North American beaver (Castor canadensis) – photo credit: wikimedia commons

Beavers are herbivores, and they harvest trees and shrubs to build dams and lodges. Their interactions with plants are legion, and so what better way to introduce the concept of animal-mediated seed dispersal than beavers. Plants have several strategies for moving their seeds around. Wind and gravity are popular approaches, and water is commonly used by plants both aquatic and terrestrial. Partnering with animals, however, is by far the most compelling method. This strategy is called zoochory.

Zoochory has many facets. Two major distinctions are epizoochory and endozoochory. In epizoochory, seeds become attached in some form or fashion to the outside of an animal. The animal unwittingly picks up, transports, and deposits the seeds. The fruits of such seeds are equipped with hooks, spines, barbs, or stiff hairs that help facilitate attachment to an animal’s fur, feathers, or skin. A well known example of this is the genus Arctium. Commonly known as burdock, the fruits in this genus are called burs – essentially small, round balls covered in a series of hooks. Anyone who has walked through – or has had a pet walk through – a patch of burdocks with mature seed heads knows what a nuisance these plants can be. But their strategy is effective.

The burs of Arctium - photo credit: wikimedia commons

The burs of Arctium – photo credit: wikimedia commons

Endozoochory is less passive. Seeds that are dispersed this way are usually surrounded by fleshy, nutritious fruits desired by animals. The fruits are consumed, and the undigested seeds exit out the other end of the animal with a bit of fertilizer. Certain seeds require passage through an animal’s gut in order to germinate, relying on chemicals produced during the digestion process to help break dormancy. Other seeds contain mild laxatives in their seed coats, resulting in an unscathed passage through the animal and a quick deposit. Some plants have developed mutualistic relationships with specific groups of animals regarding seed dispersal by frugivory. When these animal species disappear, the plants are left without the means to disperse their seeds, which threatens their future survival.

Beavers rely on woody vegetation to get them through the winter, but in warmer months, when herbaceous aquatic vegetation is abundant, such plants become their preferred food source. Water lilies are one of their favorite foods, and through both consumption of the water lilies and construction of wetland habitats, beavers help support water lily populations. This is how John Eastman puts it in The Book of Swamp and Bog: “Beavers relish [water lilies], sometimes storing the rhizomes. Their damming activities create water lily habitat, and they widely disperse the plants by dropping rhizome fragments hither and yon.”

Fragrant water lily (Nympaea odorata) - photo credit: wikimedia commons

Fragrant water lily (Nymphaea odorata) – photo credit: wikimedia commons

The seeds of water lilies (plants in the family Nymphaceae) are generally dispersed by water. Most species (except those in the genera Nuphar and Barclaya) have a fleshy growth around their seeds called an aril that helps them float. Over time the aril becomes waterlogged and begins to disintegrate. At that point, the seed sinks to the bottom of the lake or pond where it germinates in the sediment. The seeds are also eaten by birds and aquatic animals, including beavers. The aril is digestible, but the seed is not.

In her book, Once They Were Hats, Frances Backhouse writes about the relationship between beavers and water lilies. She visits a lake where beavers had long been absent, but were later reintroduced. She noted changes in the vegetation due to beaver activity – water lilies being only one of many plant species impacted.

Every year in late summer, the beavers devoured the seed capsules [of water lilies], digested their soft outer rinds and excreted the ripe undamaged seeds into the lake. Meanwhile, as they dredged mud from the botom of the lake for their construction projects, they were unintentionally preparing the seed bed. Seeing the lilies reminded me that beavers also inadvertantly propagate willows and certain other woody plants. When beavers imbed uneaten sticks into dams or lodges or leave them lying on moist soil, the cuttings sometimes sprout roots and grow.

Other facets of zoochory include animals hoarding fruits and seeds to be eaten later and then not getting back to them, or seeds producing fleshy growths that ants love called elaiosomes, resulting in seed dispersal by ants. Animals and plants are constantly interacting in so many ways. Zoochory is just one way plants use animals and animals use plants, passively or otherwise. These relationships have a long history, and each one of them is worth exploring and celebrating.

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Drought Tolerant Plants: Pearly Everlasting

Despite being such a widely distributed and commonly occurring plant, Anaphalis margaritacea is, in many other ways, an uncommon species. Its native range spans North America from coast to coast, reaching up into Canada and down into parts of Mexico. It is found in nearly every state in the United States, and it even occurs throughout northeast Asia. Apart from that, it is cultivated in many other parts of the world and is “weedy” in Europe. Its cosmopolitan nature is due in part to its preference for sunny, dry, well-drained sites, making it a common inhabitant of open fields, roadsides, sandy dunes, rocky slopes, disturbed sites, and waste places.

Its common name, pearly everlasting, refers to its unique inflorescence. Clusters of small, rounded flower heads occur in a corymb. “Pearly” refers to the collection of white bracts, or involucre, that surround each flower head. Inside the bracts are groupings of yellow to brown disc florets. The florets are unisexual, which is unusual for plants in the aster family. Plants either produce all male flowers or all female flowers (although some female plants occasionally produce florets with male parts). Due to the persistent bracts, the inflorescences remain intact even after the plant has produced seed. This quality has made them a popular feature in floral arrangements and explains the other half of the common name, “everlasting.” In fact, even in full bloom, the inflorescences can have a dried look to them.

pearly-everlasting-6

Pearly everlasting grows from 1 to 3 feet tall. Flowers are borne on top of straight stems that are adorned with narrow, alternately arranged, lance-shaped leaves. Stems and leaves are gray-green to white. Stems and undersides of leaves are thickly covered in very small hairs. Apart from contributing to its drought tolerance, this woolly covering deters insects and other animals from consuming its foliage. In The Book of Field and Roadside, John Eastman writes, “Insect foliage feeders are not numerous on this plant, owing to its protective downy ‘gloss.’ … The plant’s defensive coat seems to prevent spittlebug feeding on stem and underleaves. The tomentum also discourages ant climbers and nectar robbers.”

pearly-everlasting-5

Not all insects are thwarted however, as Anaphalis is a host to the caterpillars of at least two species of painted lady butterflies (Vanessa virginiensis and V. cardui). Its flowers, which occur throughout the summer and into the fall. are visited by a spectrum of butterflies, moths, bees, and flies.

Because the plants produce either male or female flowers, cross-pollination between plants is necessary for seed development. However, plants also reproduce asexually via rhizomes. Extensive patches of pearly everlasting can be formed this way. Over time, sections of the clonal patch can become isolated from the mother plant, allowing the plant to expand its range even in times when pollinators are lacking.

The attractive foliage and unique flowers are reason enough to include this plant in your dry garden. The flowers have been said to look like eye balls, fried eggs, or even, as Eastman writes, “white nests with a central yellow clutch of eggs spilling out.” However you decide to describe it, this is a tough and beautiful plant deserving of a place in the landscape.

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Photos in this post are of Anaphalis margaritacea ‘Neuschnee’ and were taken at Idaho Botanical Garden in Boise, Idaho.

Poisonous Plants: Heartbreak Grass

An Asian vine known to be deadly poisonous has been in the news lately. Alexander Perepilichny, a Russian banker turned whistleblower who provided information on tax fraud committed by the Russian state and the Russian Mafia, mysteriously died while jogging back in November 2012. Last year, a botanist at Royal Botanic Gardens, Kew was called in to help with the ongoing investigation. Analyses revealed traces of a compound found in Gelsemium elegans, suggesting that Perepilichny had been poisoned and calling into question the orignal claim that there was no foul play in his death.

Gelsemium is a genus in the family Gelsemiaceae. It is composed of three species, two of which are native to North America (G. rankinii and G. sempervirens). Gelsemium elegans is native to China and Southeast Asia. All species are poisonous due to a number of alkaloids found in virtually all parts of the plant and particularly concentrated in the roots and leaves. The most toxic and abundant compound is gelsemine, an alkaloid related to strychnine.

Gelsemium elegans, commonly known as heartbreak grass, is a twining vine with oppositely arranged, narrowly ovate leaves and yellow to orange flowers with five petals that are fused near the base. It occurs in thickets and scrubby forests. According to news reports (NPR and ABC News), it has a history of being used in assassinations by Chinese and Russian contract killers. Finding traces of it in Perepilichny’s body understandably raises questions about his death. The investigation continues, and the Kew botanist is now a “star witness.” 

Gelsemium elegans (image credit: Flora of China)

Gelsemium elegans (image credit: Flora of China)

Poisoning by heartbreak grass is not a pleasant experience. Its affects can be felt soon after ingestion and, depending on the amount ingested and the time that lapses between ingestion and treatment, death – usually by asphyxiation – can be imminent. The Hong Kong Journal of Emergency Medicine reported on two cases of Gelsemium elegans poisoning, in which a husband and wife consumed the plant after mistaking it for the medicinal herb, Mussaenda pubescens. The 65 year old woman became dizzy, weak, and nauseous thirty minutes after consuming the plant. Then she went unconscious. Quick medical attention saved her life. She was released from the hospital eight days later, after spending time in intensive care and undergoing various treatments. Her 69 year old husband experienced similar dizziness and weakness, but promptly vomited and called for an ambulance.

The report states that “ingestion of G. elegans is highly poisonous regarding its neurological and respiratory depressive effects,” and that “early and active respiratory support is the key to successful resuscitation.” The report also wisely warns: “People should best avoid eating any wild plants because of the similar external appearance of certain poisonous and non-poisonous species.” Proper and skilled identification is paramount, especially where plants are growing so closely together that they intertwine, “leading to inadvertent ingestion.”

All Gelsemium species have been used medicinally to treat a variety of ailments. If used properly, they may provide effective treatments; however, in their book, The North American Guide to Common Poisonous Plants and Mushrooms, Nancy Turner and Patrick von Aderkas state – regarding the medicinal use of G. sempervirens – that the “plant [is] considered very dangerous for herbal use.” They also list the plant as a skin and eye irritant and claim that the flower’s nectar produces poisonous honey.

gelsemium sempervirens 1

Gelsemium sempervirens

Commonly known as Carolina jasmine and yellow jessamine, G. sempervirens is a woodland plant found in west Texas and throughout the southeastern United States. It is an attractive, evergreen, perennial vine with yellow, fragrant, funnel-shaped flowers and is grown as an ornamental in its native region and beyond. Most poisonings occur when the stems and leaves are consumed, usually as some kind of “herbal preparation;” however, the Handbook of Poisonous and Injurious Plants claims that “there are cases of children who were poisoned after sucking on the flowers.” Headaches, dizziness, blurred visions, dry mouth, and difficulty speaking and talking are a few of the initial symptoms experienced after ingesting this plant. When cases are severe, muscles in the body experience weakness, spasms, and contractions. Symptoms, in other words, are akin to strychnine poisoning, and barring prompt and proper medical care, results can be similarly deadly.

More Poisonous Plants Posts:

The Problem with ‘Yes’ Landscapes

This is a guest post by Jeremiah Sandler. Follow Jeremiah on Instagram @j4.sandler

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I don’t work for a landscape company, nor have I ever worked for one. The company I do work for contracts with these companies to do health care on their landscapes. For example, we scout for insects and diseases, spray pesticides when necessary, make recommendations of proper cultural practices, and fertilize.

Something has been bothering me for the past two years about the landscapes in metropolitan southeast Michigan. Both commercial and residential landscapes have at least two things in common: the same plants, and the same poor management of these plants. The clients have no idea they’re being ripped off.

The landscape companies I have experience with seem to think the homeowner is always right.

The ‘Yes’ Conversation

You want a Colorado blue spruce in humid Michigan? Sure, no problem. Let’s put six trees within 15 square feet. Don’t bother removing the cage and burlap. We also won’t tell you the massive expense you’ll pay in the future to spray fungicides on your spruce to keep it alive. If one dies, we’ll just replace it with the same plant.

You want a green hedge? Boxwoods or yews. They’ll be sheared multiple times a year by our crew of expert (and underpaid and exhausted) workers. At the first sign of new growth, we’ll be there mutilating your plants to ensure that they stay at right angles. You see all of those ripped apart, discolored leaves on your shrubs? Ignore that; plants are meant to be tamed into perfect geometry. Oh, that’ll be an extra charge to spray insecticides and fungicides.

Here’s a list of plants you can get to add to the monotony in your neighborhood: crabapple, hawthorn, cherry, honeylocust, blue spruce, oak, red maple, Japanese maple, pear, white pine, boxwood, yew, hydrangea, arborvitae, burning bush, and wax begonias.

Why is your hemlock tree neon yellow? We don’t know, let’s just replace it. Why is your Norway maple declining? Well, when we planted it, we kept the cage on its root ball, despite this tree having notorious girdling roots. Let’s get you a new one. Why are some of your shrubs rotting out? We left the soaker hoses on them for years and kept them running regularly. Yes we can spray all of your plants. We can kill everything before it’s a problem.

We’re the best landscapers in town! Our services are top of the line, and we guarantee your landscape will look exactly the same as your neighbor’s.

That’s a very sardonic, hypothetical conversation between a homeowner and a landscape company. A sensible company knows you don’t know best. As a homeowner, it is wise to heed the advice of a company’s horticulturist. Cost is always a consideration for the homeowner. However, the more expensive company is not always the highest quality. Here’s why.

So, you want a Colorado blue spruce?

A responsible company won’t let you plant a blue spruce in a place with wet springs and humid summers. They will tell you why it is not a good idea, and they will suggest alternatives. For example, a concolor fir (Abies concolor) looks similar to a blue spruce. They are resistant to needle cast diseases and cytospora canker, and they can tolerate southeast Michigan’s alkaline soils. In the long run, it is much cheaper to get the right plant in the right place.

You will pay more for your blue spruce because, not only are you paying for installation, you are paying to spray fungicides year after year to avoid having a skeleton in your yard. Companies know there is a likelihood of replacing your newly planted blue spruces, so you are charged for it.

We love boxwoods and so do you

Maybe you do like the classic, formal look of hedges. And maybe you do like the texture offered by a boxwood or yew. That’s fine. This is the problem I see literally every single day: over-shearing.

An appropriate cultivar selection is the answer. Cultivars and hybrids exist which only grow to x-amount tall and x-amount wide. Simply read the tag from the nursery. If your landscape company planted the proper plants the first time, they wouldn’t be able to charge you as much as they do to “maintain” them. The right plants in the right places need very little maintenance. I will concede, a few plants can tolerate being sheared. Once in a great while is acceptable; not three times a year.

Excessive shearing stresses out a plant. In fact, certain chemicals released by the open wounds of the leaves attract insects. Wet, exposed tissue serves as a breeding ground for fungi. Some of the problems your shrubs face are directly caused by the shearing itself.

PlantAmnesty, a website dedicated to stopping bad pruning practices states:

Any pruning book will explain that one prunes to open up the center of the plant, allowing air and light penetration to make the plant healthy. Shearing, on the other hand, creates a twiggy outer shell that gets ever denser and collects more deadwood and dead leaves every year, the opposite of a healthy condition. The results create the perfect protected place for pests and diseases, akin to locking up the house so the garbage can’t be removed. After many years, this treatment can lead to disease and general bad health without actually being a disease itself. If plants have mites and blights, bugs and mildews galore, how they were pruned may be the root of the problem.

Not to mention, the plant is spending all of its energy regrowing those leaves you continually cut off. There are correct ways to prune plants, and none of them include the excessive use of motorized shears. A plant grows to reach an equilibrium with its environment. If the environment is adequate, the plant will grow. If the environment is unfavorable, the plant will decline. In other words, if it is growing, let it grow!

What’s a monoculture?

There seems to be only 15 plants which are acceptable to the landscaper. The plant selection is predictable. Certainly there are more than 15 different species of plants you can have on your property. Sure, some redundant species are okay: white pines, oaks, maples (except that damned Norway maple). I don’t want to discourage people from exploring new options, though.

Native plants offer easy beauty. They have evolved in your region for millennia and are therefore adapted to your environmental conditions. These plants often tolerate both biological and environmental stressors better than non-native plants. Expenses are saved when you don’t have to pay for disease control. You wouldn’t buy a vehicle, for example, that you know would break down and require fixing all the time.

There are dozens of other shrub options for texture, winter interest, privacy walls, etc., that you don’t have to hire a crew to shear every month. Surprisingly, some large yucca species are hardy in colder zones, which offer a different texture. Red-twig dogwoods provide colorful winter interest; there are red, green, and yellow-stemmed cultivars. Coyote willow is native to southeast Michigan. It is a thin-leafed, rhizomatous Salix species which forms beautiful yellow walls in the fall. An entire, separate article can be written on the subject of alternatives. Just know there are plenty of species to choose from no matter where you live.

Ask, and you shall receive

This request comes from homeowners and is often fulfilled by companies: “Can’t you just spray it?” Granting this request is entirely wrong. One cannot, by law and by principle, go around as a pesticide desperado. You live in that environment. Why would you want pesticides in excess? Chemicals are used as a last resort and strictly on an as needed basis.

Appropriate timing, safety precautions, and proper insect identification are all legally required before insecticides can be applied. Some of the ‘yes’-type companies will comply with all uneducated (and sometimes unsafe) requests.

Some of the appointments I have with customers address very rudimentary horticultural problems. The homeowner’s concerns are legitimate. Most problems they are having, though, can be avoided with an ounce of foresight. Issues include planting hemlock trees in full sun, or replacing a Japanese maple killed by verticillium wilt with another Japanese maple. The list goes on…

Saying ‘No’

There’s a myriad of things that can go wrong in a landscape. It is an artificial environment containing plants which evolved continents apart. Plants often don’t have the capacity to combat pathogens that they are not exposed to in their native habitats, but certain issues are impossible to predict. There is a base knowledge one should have before making these kinds of decisions. The “customer is always right” philosophy doesn’t apply in this domain. You should have some creative influence on your landscape; it’s yours, after all. Spend the time in the nursery looking for interesting plants, make a list, and run it by your landscaper. If they say ‘yes’ to all of your choices, fire them. The people you hire cannot be too timid to tell you ‘no’ sometimes.

“Right plant, right place” is the mantra among plant health care technicians. We are the people who have to clean up the messes made by your landscapers. If your landscaper did their job with longevity in mind, I probably wouldn’t have much to do.