In Praise of Poison Ivy

This is a guest post by Margaret Gargiullo. Visit her website, Plants of Suburbia, and check out her books for sale on Amazon.

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No one seems to like Toxicodendron radicans, but poison ivy is an important plant in our urban and suburban natural areas. Poison ivy (Anacardiaceae, the cashew family) is a common woody vine, native to the United States and Canada from Nova Scotia to Florida, west to Michigan and Texas. It is also found in Central America as far south as Guatemala. It is all but ubiquitous in natural areas in the Mid-Atlantic United States. It has been recorded in over 70 wooded parks and other natural areas in New York City.

Leaflets of three? Let if be. Poison ivy (Toxicodendron radicans). photo credit: wikimedia commons

Leaflets of three? Let if be. Poison ivy (Toxicodendron radicans) – photo credit: wikimedia commons

Poison ivy does have certain drawbacks for many people who are allergic to its oily sap. The toxins in poison ivy sap are called urushiols, chemicals containing a benzene ring with two hydroxyl groups (catechol) and an alkyl group of various sorts (CnHn+1).

These chemicals can cause itching and blistering of skin but they are made by the plant to protect it from being eaten by insects and vertebrate herbivores such as rabbits and deer.

Poison ivy is recognized in summer by its alternate leaves with three, shiny leaflets and by the hairy-looking aerial roots growing along its stems. In autumn the leaves rival those of sugar maple for red and orange colors. Winter leaf buds are narrow and pointed, without scales (naked). It forms extensive colonies from underground stems and can cover large areas of the forest floor with an understory of vertical stems, especially in disturbed woodlands and edges. However, It generally only blooms and sets fruit when it finds a tree to climb. When a poison ivy stem encounters a tree trunk, or other vertical surface, it clings tightly with its aerial roots and climbs upward, reaching for the light (unlike several notorious exotic vines, it does not twine around or strangle trees). Once it has found enough light, it sends out long, horizontal branches that produce flowers and fruit.

Flowers of poison ivy are small and greenish-white, not often noticed, except by the honeybees and native bees which visit them for nectar and exchange pollen among the flowers. Honey made from poison ivy nectar is not toxic. Fruits of poison ivy are small, gray-white, waxy-coated berries that can remain on the vine well into winter. They are eaten by woodpeckers, yellow-rumped warblers, and other birds. Crows use poison ivy berries as crop grist (instead of, or along with, small stones) and are major dispersers of the seeds.

The fruits of poison ivy (Toxicodendron radicans) - photo credit: Daniel Murphy

The fruits of poison ivy (Toxicodendron radicans) – photo credit: Daniel Murphy

It is as a ground cover that poison ivy performs its most vital functions in urban and suburban woodlands. It can grow in almost any soil from dry, sterile, black dune sand, to swamp forest edges, to concrete rubble in fill soils, and along highways. It enjoys full sun but can grow just fine in closed canopy woodlands. It is an ideal ground cover, holding soil in place on the steepest slopes, while collecting and holding leaf litter and sticks that decay to form rich humus. It captures rain, causing the water to sink into the ground, slowing runoff, renewing groundwater, filtering out pollutants, and helping to prevent flooding.

Poison ivy is usually found with many other plants growing up through it – larger herbs, shrubs, and tree seedlings that also live in the forest understory. It seems to “get along” with other plants, unlike Japanese honeysuckle or Asian bittersweet, which crowd out or smother other plants. Poison ivy is also important as shelter for birds and many invertebrates.

While those who are severely allergic to poison ivy have reason to dislike and avoid it, Toxicodendron radicans has an important place in our natural areas. No one would advocate letting it grow in playgrounds, picnic areas, or along heavily used trail margins, but it belongs in our woods and fields and should be treated with respect, not hatred. Recognize it but don’t root it out.

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Further Reading: Uva, R. H., J.C. Neal and J. M. DiTomaso. 1997. Weeds of the Northeast. Comstock Publishing. Ithaca, NY.

This piece was originally published in the New York City Dept. of Parks & Recreation, Daily Plant.

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Cedar Confusion

This is a guest post by Jeremiah Sandler. Words by Jeremiah. Photos by Daniel Murphy (except where noted).

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What makes a cedar a cedar?

I recently asked this question to a professor of mine because I kept hearing individuals in the field refer to many different species as “cedars”. It was puzzling to me because, being the taxonomy-nerd that I am, most of these plants are in entirely different plant families but still called the same thing. Yes, sometimes common names overlap with one another regionally; avoiding that mix up is the purpose of binomial nomenclature in the first place! So, what gives?! Why are 50+ different species all called cedars?

This professor is a forester, not a botanist. He told me the word “cedar” describes the wood. Turns out, after some research and conversation, that’s all there was to it. As defined by Google, a cedar is:

Any of a number of conifers that typically yield fragrant, durable timber, in particular.

Cedar wood is a natural repellent of moths, is resistant to termites, and is rot resistant. A good choice of outdoor lumber.

I was hoping to find either a phylogenetic or taxonomic answer to what makes a cedar a cedar. I didn’t. Taxonomic relationships between organisms are one of the most exciting parts of biology. Thankfully, some solace was found in the research:

There are true cedars and false cedars.

True cedars are in the family Pinaceae and in the genus Cedrus. Their leaves are short, evergreen needles in clusters. The female cones are upright and fat, between 3 – 4 inches long. Their wood possesses cedar quality, and they are native to the Mediterranean region and the Himalayas.

False cedars are in the family Cupressaceae, mostly in the following genera: Calocedrus, Chamaecyparis, Juniperus, and Thuja. Their leaves are scale-y, fan-like sprays. Female cones are very small, about half an inch long, and remain on the tree long after seed dispersal. The bark is often both reddish and stringy or peely. Their wood possesses cedar quality. It is easy to separate them from true cedars, but less obvious to tell them from one another. These false cedars are native to East Asia and northern North America.

I couldn’t do away with the umbrella term “cedar.” Every naturalist can agree that one of the most pleasurable things while outdoors looking at plants is identifying them. I have set a new objective to correctly identify and differentiate between all of the cedars and false cedars, rather than simply calling them cedars. I guess I’m just fussy like that.

Influence of a Passion

This is a guest post by Samuel Malley.

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One of the most fascinating parts of plant interest is learning about those who have contributed to it as a whole. It has inspired great men and women who made it what it is today – from the Greek Theophrastrus, regarded as the father of botany through to Margaret Rebecca Dickinson who would bring these plants to life through illustrations. To learn about their lives is an absolute joy, knowing your passion has birthed these amazing people.

Take Carl Linnaeus, for example, a man who invented a method to name plants according to their genus, species, and so forth. We use this commonly today as it has become his legacy that impacts every botanist, gardener, and horticulturist as well as many others in the world. As the Roman naturalist Pliny the Elder would say “fortune favours the brave.” This quote would certainly apply to many. The dream to travel to new far away lands and discover new plant species would indeed inspire those willing to be brave and be rewarded in return. Even now in this day and age people are still imagining and travelling to see what else is out there. And who knows, a plant could be discovered soon that pushes the boundaries of what we think and know.

One of the first botanists I came across just as my obsession was starting was Luca Ghini. Born in 1490, he created the first botanical garden in Pisa, Italy. Ghini also created a technique of drying and pressing plants, eventually being recorded with having the first herbarium. This supposedly contained around three hundred specimens.

To me Luca is one of my personal heroes – someone who’s genius shaped the modern plant world. What a privilege it must have been to be the first to have stepped into the Pisa Garden or to be in the company of Luca as he added a new leaf to his collection. He passed away in 1556, and like every great botanist he left a legacy. Ghini is still here, alive through his garden and his drying technique. To the man himself, if I could go back in time, the two words that I would say to him would be, “Thank you.”

Pisa Botanical Garden - photo credit: Chris / flickr

Pisa Botanical Garden – photo credit: Chris/Flickr

The future ahead in plant interest is a very bright one, awaiting more great people to add to the rich, fascinating history it has to offer full of eye opening men and women.

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Samuel Malley is a horticulture student in the United Kingdom. He is an aspiring botanist and is also interested in creating unique garden sculptures. 

The Problem with ‘Yes’ Landscapes

This is a guest post by Jeremiah Sandler. Follow Jeremiah on Instagram @j.deepsea

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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.

Confidential Carnivore

This is a guest post. Words and images by Jeremiah Sandler

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If you live in North America or Europe, chances are you have seen Dipsacus fullonum, commonly called teasel.  Its tall (up to 2 meters), spiky flower stalks with large purple flowers are easy to spot in low-lands, ditches, or along highways.  Since this prolific seeder’s introduction to North America from Europe, it has steadily increased its habitat to occupy nearly each region of the United States. Of course, like all plants, teasel has its preferences and is more frequent in some areas than in others.

dipsacus fullonum_jeremiah sandler

Teasel is an unassuming, herbaceous biennial.  It takes two years to complete its life cycle: First-year growth is spent as a basal rosette, and second-year growth is devoted to flowering.  Standard biennial, right?  As of 2011, an experiment was conducted on this plant that changed the way we see teasel, and possibly all other similar plants.

“Here we report on evidence for reproductive benefits from carnivory in a plant showing none of the ecological or life history traits of standard carnivorous species.” -Excerpt from the report titled Carnivory in the Teasel Dipsacus fullonum — The Effect of Experimental Feeding on Growth and Seed Set by Peter J.A. Shaw and Kyle Shackleton.

We all have favorite carnivorous plants, Venus flytraps, pitcher plants, sundews, etc.. Their showy traps and various means of attracting insects are all marvels of evolution in the plant kingdom.  These insectivorous plants evolved these means of nutrient acquisition in an answer to the lack of nutrients in their environment’s soil.  In some of these plants, there is a direct relationship between number of insects consumed and the size of the entire plant. In others, there is no such relationship.

The unassuming, biennial teasel can now join the ranks of carnivore, or protocarnivore.  It didn’t evolve in bogs or swamps where soil nutrients are depleted.  It has no relationship to the standard carnivorous species. It doesn’t have any flashy traps. In fact, it has no obvious traits which suggest it can gain nutrients from insects. Teasel’s carnivorous habits can be likened somewhat to the carnivorous habits of bromeliads; water gathered in their leaves traps insects.

In Shaw and Shackleton’s experiment (done in two field populations), maggots were placed in water gathered in the center of some first-year rosettes of teasel.  Other rosettes in the same population were left alone as controls.  Not surprisingly, the teasels which were ‘fed’ larvae did not change in overall size.  The size of the overwintering rosette did not offer any predictability towards the size of flower shoots for the coming year. However, something strange did happen:

“…addition of dead dipteran larvae to leaf bases caused a 30% increase in seed set and the seed mass:biomass ratio.”…“These results provide the first empirical evidence for Dipsacus displaying one of the principal criteria for carnivory”

Teasel has some physiology to absorb nutrients from other macroorganisms despite teasel evolving in an entirely different setting than typical carnivorous plants.  Teasel’s already proficient reproductive capacity is enhanced by using insects as a form of nutrients in a controlled setting.  

Many exciting questions have been raised by this experiment. How has this absorption mechanism come about, without the obvious use of lures or other structures to attract insects? And how does teasel maximize upon its own morphology in the wild, if at all?  What would the results be if these experiments were recreated on other similar species?

There are studies being conducted all the time that further the boundaries of what we know about these stationary organisms. There are new discoveries waiting just around the corner. Carnivory in plants is amazing because it transcends common notions about plants; especially in the case of the unassuming teasel.

Selected Resources:

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Jeremiah Sandler lives in southeast Michigan where he works in the plant health care industry. He has a degree in horticultural sciences and is an ISA certified arborist. He is interested in all things plant related and plans to own a horticulture business where he can share his passion with others. Follow Jeremiah on Instagram: @j.deepsea

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