31 July 2018

Threat of Giant Hogweed Invasion Found to be Giant Hogwash

First, a story:

When I was gardening at Great Dixter some years ago, I met one of the bad boys of the plant world: Giant Hogweed. I remember the encounter quite well, particularly because of Fergus's stern admonition as to what might happen if we didn't heed his warnings about how to approach it. While Giant Hogweed looks pretty and impressive, this plant's sap can cause severe burns on exposed skin and if it gets in your eyes, well, it's bad. Really bad. Like, go to the hospital and probably should learn Braille, bad.

So there we were, the four of us, charged with the task of ridding the garden of a particularly large specimen. The reason I remember this so clearly is because three of us took precaution to the next level with tall boots and long socks, long trousers, long sleeves, heavy gloves, goggles, hats, and bandannas over our faces. We looked like a crew of botanical outlaws! All but the French intern, who took up the machete with a glint in her eye and started slashing the thug to bits, wearing only trainers with short socks, running shorts, and a tank top. Amazingly, she suffered no harm and together we vanquished the enemy, reducing its 12' height and about 8' width into several sturdy garbage bags. 

So when the sensational news recently came out about the state of Virginia being invaded by a whole colony of Audrey-like marauding Giant Hogweed, I noticed because I live here now. Since I had lived to tell the tale of my English encounter with the weed, I really didn't see what the big deal was but the news made it all the way across the country and I started receiving concerned emails from friends in California. Surely an authority in the plant world would come forth and set the record straight but it took several days of hearing about it on the radio and seeing it plastered all over the internet and social media before anyone did.

My favorite headline was from the New York Times, cheekily borrowing that soothing phrase from The Hitchhiker's Guide to the Galaxy, 'Don't Panic!' after warning of burns and blindness.

So what is this pestilential plant and should you be worried about it? The short answer is no, but let's start with properly identifying it and how to deal with it, if found.

A poster warning of the harmful effects of exposure to Giant Hogweed sap.
New York State Department of Environmental Conservation

Plant names often contain hints as to a plant's physical characteristics and Giant Hogweed is just that - giant. It can reach 15' in height and the leaves can be upwards of 5' wide with stems up to 4" in diameter. To say it has presence is an understatement and so isn't something you're likely to accidentally brush against on a hike. You'd really have to blunder into it in a big way. The airy white flowers form an umbel (same root word as 'umbrella') which reveal its relation to the carrot family (which also includes the common culinary herbs parsley, fennel, anise, celery, coriander, cumin, and dill) but please don't try to eat it! 

Since it seems so easy to identify, why all the sensationalism? There are several other plants in the same family here on the east coast that may be mistaken for the Giant Hogweed and since some can cause adverse reactions through touch or ingestion, it's important to know the difference. Here in NoVA a more diminutive cousin, Queen Anne's Lace (Daucus carota), is a common and prolific wildflower; however, another cousin, Poison Hemlock (Conium maculatum), also grows in this region. I made it my personal mission to be able to identify them when a former employee kept insisting that the Queen Anne's Lace in the garden was in fact Poison Hemlock and nothing I said or showed him could convince him otherwise. My conclusion: he was not a person I wanted to be stuck in a forest with having to forage for food because he would surely kill us.

But I digress.

Instead of plodding through all the plants to avoid, it seems easier to me to identify the one that's safe, or least likely to eat you alive. Anything else that looks similar but doesn't display the same characteristics probably should be avoided. At best, one should use common sense and proper PPE (personal protective equipment) when dealing with this family if you don't know precisely who you're dealing with.

Daucus carota, commonly known as Queen Anne's Lace or wild carrot, is an herbaceous biennial that grows about 3' tall. The stems are green, rough, hairy, and solid when cut. The small white flowers form a dense umbel (there's that word again) with a purple flower in the center.

An umbel of Queen Anne's Lace in full flower. Notice the purple flower in the center. Notice also that I'm touching the stem with no glove on. Some people may experience an irritating reaction from the hairy stem, and those who are photosensitive may get blisters from exposure to the sap.

A Queen Anne's Lace umbel in profile. The stems are hairy and completely green, with no blotches of color.
The solid core of a cut stem of Queen Anne's Lace.

Meet 'Dara', a colorful ornamental variety of Daucus carota. She still sports a darker purple center.

To me, the most immediate way of telling the wild carrot apart from Poison Hemlock is to cut it. If the stem is hollow, step away. After all, this is the plant that killed Socrates. Unlike the Queen, Poison Hemlock grows taller, has smooth stems with purple blotches, the umbel isn't as dense and the purple center is conspicuously absent.


For those in the know, neither Queen Anne's Lace or Poison Hemlock can be confused with Giant Hogweed, seeing as it's so much bigger than either of them. That's why it's handy, not to say important, to Know. Your. Plants. As Marie Curie once said, "Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less". Knowing what Giant Hogweed is in the first place, and understanding how to deal with it in the second, means you shouldn't have anything to fear. I don't for those reasons, and because I had a good teacher who didn't just send a bunch of novices to deal with a dangerous plant without properly arming us first. 

So what should you do if you think you spot one? First of all, Don't Panic! And don't touch* it if you're not sure what it is. Take a few photos of the leaf, stem, and flowers and send them to your local Cooperative Extension agent. This guide from VA Tech has a table showing the differences between several similar plants that are often confused and this handy media advisory, which also says to not panic and indicates that the population isn't spreading and there's really nothing much to worry about after all, provides more information on how to report it if you think you've spotted it. 

So, forewarned is forearmed and understanding eliminates fear. If that doesn't convince you and all the Giant Hogweed hullabaloo still gives you nightmares, just remember:

*Giant Hogweed sap is phototoxic and causes severe skin inflammation when contacted skin is exposed to UV rays. If contact is suspected, get out of the sun and thoroughly wash affected area with soap and water. If irritation persists, consult a physician. If it gets in your eyes, rinse immediately with clean water and seek medical attention.

01 May 2017


"The very word May, short and direct, seems full of light and ready to become airborne. Man compares himself with the world around him, with the birds shouting their songs, the trees bursting into leaf; old or young, in imagination or in fact, he feels himself a part of this great creative impulse."

Christopher Lloyd in Christopher Lloyd's Gardening Year

19 February 2017

Shakespeare in the Garden

I've been trying to come up with new ways to keep my crew at work motivated and to convey the daily task list in a less monotonous form (because, let's face it, gardening isn't all glamorous work, sometimes we have to get our hands dirty).

This week I'm going to try a Shakespearean approach and see how it goes:

GARDENER [to the first man]
       Go, bind thou up young dangling apricots
Which, like unruly children, make their sire
Stoop with oppression of their prodigal weight.
Give some supportance to the bending twigs.
[to second man] Go thou, and, like an executioner, 
Cut off the heads of too fast-growing sprays
That look too lofty in our commonwealth.
All must be even in our government.
You thus employed, I will go root away
The noisome weeds which without profit suck
The soil's fertility from wholesome flowers.

[The Tragedy of King Richard the Second, Act III, Scene IV]

16 February 2017

Oh, Deer

One of my favorite TV shows growing up was Mutual of Omaha's Wild Kingdom. Each week I'd watch the ivory mustachioed host, Marlin Perkins, traverse the globe presenting exciting tales of wildlife conservation. It was probably my first exposure to conservation issues and corporate sponsorship. For a kid growing up in Suburbia it was all about exotic locations and wild beasts that I would probably never have the chance to see up close and personal.
Then I became a gardener and moved to the east coast.

Every region of the world has their native pests that are the bane of a gardener's existence: in So Cal it's gophers and grubs; in England it's badgers and tourists; here in the Mid-Atlantic it's white-tailed deer.

A mature buck lounges in the Pachysandra, digesting his lunch

When I arrived as Director of Horticulture at my former employer several years ago, I was surprised to find a small herd of Odocoileus virginianus in residence. The fence surrounding the property had been breached several times due to storms and vandalism. A few attempts to drive the deer out proved unsuccessful and the deer were happily noshing the garden away.

One way to tell you have a deer problem in a wooded area is if you can see through the forest. The absence of an understory and ground cover layer are indicative of over browsing. Deer are native plant connoisseurs and will munch all the desirable plants that other birds and insects rely on for food and shelter, creating an imbalance in the local ecosystem. One day I popped out of the laundry room at home and came face to face with a herd in the parking lot. These deer were munching their way along the stream out back but I noticed they neatly avoided the boulder covered with budding poison ivy (apparently they know the poison ivy mantra, too).

According to experts, the numbers of white-tailed deer currently roaming the streets is way more than it was when Colonists first settled the eastern sea board 300 years ago. Native Americans and arriving settlers would hunt deer for their meat and hides. Natural predators also kept the populations in check, maintaining balance in the ecosystem. Then the human population boomed, cities were built, habitat was destroyed. The number of deer plunged and laws were passed to save them resulting in an exponential increase in the population. With no habitat left, they began to infiltrate the suburbs and remaining forest edges created by urban sprawl.

A buck and a doe out for lunch in the parking lot at my apartment
An adult deer will eat 6-8 lbs of vegetation a day. Multiply that by the eight deer that were stuck inside the fence and you'll see that the garden where I worked was on the fast track to not being a garden at all. The historic rose garden had already lost a season of bloom and the yews were nibbled to stubby twigs. Don't even get me started on the seas of New Hostas that Never Grew. I knew that controlled hunts were commonly used in larger public gardens to manage the deer so I wasted no time in organizing one.
The hunt would have to be bow because of the dense residential area, and it would have to be carefully managed. When I breached the subject I was met with much resistance: "The city would never allow it", the nay-sayers said. "Have they ever asked?" I asked. Well, er, no, they hadn't. So I asked, the city said yes, and a resolution was passed to allow a bow hunt in the garden.
As fate would have it, I connected with the Oak Ridge Sportsmen's Association, who happily satisfied the insurance requirements. They were skilled, they were experienced, they were knowledgeable, they were shocked that I got the resolution passed. So they came, they strategized, they hunted, and they got all the deer. They were awesome!
One of my requirements was that at least 75% of the deer harvested go to a food bank and I'm proud to say the hunt resulted in 320 meals being donated. Once the snow melted, you could almost hear the garden breathe a sigh of relief in the knowledge that it could get down to the business of growing again without fear of being eaten to death. As it is, the damage already done was extensive and will take years - no, decades - of wise stewardship and planning to restore. In this age of instant gratification and high speed everything, people lose sight of the fact that while it can take a herd of hungry deer (or a hurricane, or earthquake, or whatever) a very short time to decimate 6 acres of woodland, it will take much longer for it to recover. Unfortunately those people often aren't gardeners nor do they spend much time in nature. If they did they would understand that nothing in nature happens over night.
Invasive species that take advantage of the gaps created by an absence of native ones have to be eradicated and the areas replanted or the natives allowed to regenerate. New plants have to be monitored and cared for to ensure survival, and the invasives constantly beaten back until the balance is restored and nature can take care of itself again. Restoration takes a lot of work and a lot of time.
Pachysandra, a native of Asia, is a shade loving ground cover that spreads rapidly in the humus rich soil of a forest floor. Though also native to parts of SE US, it's been declared invasive by several eastern states.
Every conceivable non-lethal method had been attempted to remove the deer from the garden in the past and failed, leaving a managed hunt as the best possible option. If I hadn't pushed it through, the herd would have more than doubled in the spring (let's see, 15 deer eating 8lbs of garden each day is...times 5, carry the 1...yikes!). It's a touchy subject for many but getting rid of the deer was the only way to save the garden and save it we did (tip of the hunter orange cap to you ORSA guys!). It would have been interesting to see how the woodlands there regenerate and perhaps someone will take advantage of the opportunity now presenting itself and I'll read about it in ten years or so. 
A similar, though much larger, study was done at Yellowstone National Park which was also overrun with deer. They took more drastic measures and reintroduced a pack of wolves to do the hunting. The result was a trophic cascade - an ecological phenomenon triggered by the addition or removal of top predators and involving reciprocal changes in the relative populations of predator and prey. And while the Mutual of Omaha loving kid in me thought having Marlin Perkins cover the interaction of wolves and deer in a suburban garden, they unfortunately weren't an option.

02 December 2015

Osculate Me Under the Obligate Hemiparasite

Welcome to December and all the seasonal festivities and frivolities married to it! Few holidays have such a diverse number of traditions and customs. I mean, who came up these and why are they related to Christmas: eggnog, fruitcake, decorated conifers, socks on mantles, and swapping spit under mistletoe, just to name a few (and those are only the decidedly American holiday traditions. You should hear what they do in other countries!).

Actually, we did borrow the mistletoe thing from Britain, like most things which are so awesome and British. And the British being born gardeners, well, they know a thing or two about plants. What other culture would write a Christmas carol about holly and ivy? As the great global melting pot, not only do we often borrow foreign customs, we frequently take their plants, too. Viscum album, the native species found in Great Britain and much of Europe, having now been introduced to North America, is an evergreen plant with a woody stem which grows on and gets most of its nutrients from a host. It does photosynthesize a bit, but not much, which is what makes it a hemiparasite, and that's a compliment, really. The Latin name is likely derived from the sticky seed coating (viscum) and the color of the berries (from 'albus', meaning white).

The species native to Spain, Portugal, North Africa, Australia, and Asia is Viscum cruciatum (sounds like a Harry Potter spell, doesn't it?).

Potter Wiki (no nargles here)
All in all, there are over 80 genera with more than 900 species of Mistletoe. And the family name that these plants belong to? Wait for it....Santalaceae.

I kid you not, but it has nothing to do with Santa Claus. (Or does it? Nah.) Mistletoe is related to Sandalwood. It also happens to bloom and set fruit right around Christmas time when most other plants in the Northern Hemisphere are settling in for a long winter's nap. Once dissected, the common name is anything but complimentary. The name mistletoe comes from the Anglo Saxon word 'mistel' (which means dung, probably a reference to how the plant is propagated) and the Old English word 'tan' (which means twig). Roughly translated, mistletoe means 'poo on a stick'. Isn't that...special!

Mistletoe has been known and used in Herbalism for centuries and parts of the plant were prized by many ancient cultures for their healing properties. The Greeks used it to cure everything from menstrual cramps to spleen disorders, while over in Rome, the naturalist Pliny the Elder noted its use as a balm against epilepsy, ulcers and poisons (ironic, since the berries are poisonous to humans).

The plant’s romantic associations most likely began with the Celtic Druids of the 1st century A.D. Since mistletoe can blossom even during the frozen months of winter, the Druids came to view it as a sacred symbol of vim and vigor, and it was administered to humans and animals alike in the hope of restoring fertility (again, poison! Raising eyebrows, here). The association with fertility and vitality persisted throughout the Middle Ages. Some considered it an aphrodisiac (Poison! Does no one listen!?) owing to the allegedly sexual nature of the plant: the Y-shaped branches, white sticky juice from pearl hued ball-shaped berries hinted of...let's not venture further...ok, lets. Ironically, it's the female plant that bears the poisonous fruit while the male plant is conspicuously berry-less. Let your Freudian brain puzzle that one out over a mug of 'nog for a while.

By the 18th century mistletoe had become incorporated into Christmas celebrations around the world. The 'downstairs' class of Victorian England is credited with first recording the tradition of kissing underneath the mistletoe. Taking their cue from the Druids' and their fertility rituals, the tradition of kissing beneath the mistletoe dictated that a man was allowed to kiss any woman standing underneath the boughs, and should any woman refuse the overture, ill luck would befall her. Another variation on the tradition stated that with each kiss a berry was to be plucked from the mistletoe, and when all the berries were gone, the smooching must cease. Many a serving maid scurried into hiding when the mistletoe was hung, as described by nineteenth century writer Washington Irving: "the mistletoe, with its white berries, hung up, to the imminent peril of all the pretty housemaids."

"Ah, what an excellent specimen of Viscum album! Did you know this lovely plant is actually a parasite!? Why, it's extraordinary, really! You see, it actually grows in the branches of trees, not in the ground! Yes, isn't it remarkable? The seeds are eaten by birds, whereupon they pass through the digestive tract, or gut, and are shat out onto a tree branch where the seed sprouts by sending out rooting tendrils called haustorium..."

"Will he ever shut up and just kiss me?"

Kissing under the mistletoe caught on, surprisingly, and continues as a holiday sport to this day. I suppose of all the wacky Christmas customs, smooching under a parasitic plant is more pleasant, and infinitely more preferable, to a regifted 10-year old fruit cake.

So while you're enjoying the eggnog and petrified fruitcake at your next holiday gathering, keep an eye out for halls decked out with that most romantic of evergreens, pucker up, and whisper seductively to your sweetheart, "Osculate me under the obligate hemiparasite". That'll get hearts racing, I guarantee it!