GOLDENROD: The goldenrod’s blooming, so it must be fall. Goldenrod’s a lovely fall bloomer that’s gotten an undeserved bad rap as a major source of allergy-causing pollens. While it’s not pollen-free, it’s not the really bad guy. Goldenrod’s a friendly, photogenic native, beloved of birds, and bees, and other beneficial insects. There are at least 130 goldenrod species in North America. There’s even a seaside variety and a white one (“silver rod’). It’s a great late summer garden plant, too.

The villains are some of those easy-to-overlook weedy things with greenish flower stalks. The worst is the wind-pollinated ragweed, which blooms at the same time, and often grows in the same place as goldenrod, and which also belongs to the Aster (Composite) Family. And then there’s ragweed’s close relative the ubiquitous mugwort, which is also coming into bloom now.

RAGWEED: Starting with ragweed, not only is it the source of much human misery; but we have only ourselves to blame. All ragweed needs to get started is freshly-turned earth to expose the seeds buried in the soil, and a bit of sunshine to wake the seeds up. The seeds will wait in the soil for 40 years for the right conditions to come along before germinating.

Like poison ivy (Issue 74 and Issue 118 ), ragweed’s what we call an “enhanced species” because human behavior gives it a major ecological boost. Ragweeds thrive where the earth has been disturbed. In a way, it’s Mother Nature’s revenge for leaving her earth naked to dry out and erode. Almost daily, I read yet another new article about research confirming that we should disturb the soil as little as possible, and that we need to mulch, mulch, mulch. mulch.

Ragweed, for example, didn’t get out of hand until the European settlers along the East Coast cut down much of the forest and plowed up the land. Indeed, once I read that archeologists date the mud at the bottom of the Long Island Sound by the ragweed pollen count, which rocketed upwards in the 1800’s.

There are a good 2 dozen kinds of ragweed; our local ragweeds come in three basic types: common ragweed (Ambrosia artemisiifolia), western ragweed (Ambrosia psilostachya), and giant ragweed (Ambrosia trifida). The common’s usual knee height or less and has deeply cut “raggy” looking leaves. The Western looks like the common only it’s a lot bigger. The giant have rounded leaves with 2 to 5 pointy-tipped lobes and can reach shoulder height or more. The common and giant are annuals; the western can be annual or perennial, spreading by underground roots.

The three ragweeds have very similar flowers. The tiny flowers along the flower spikes are facing downward; so what you see are the scalloped green flower bases with the flower parts peeking out from underneath like a petticoat. The giant ragweed has tiny gold-yellow flowers; the common ’s are tan.

The giant ragweed’s flower stalks are striking green candelabras dusted with gold; the common’s are smaller and closer together so they like more like a crowd of slightly curved green spires

MUGWORT: Now for the mugwort (Artemisia vulgaris), also called “common wormwood”. This one’s an alien, so again, we only have ourselves to blame. It’s another one of the Euro-Asian imported herbs that got out of hand. Along long the East Coast, across the Midwest and in the Northwest, you’ll see the silvery, plumy colonies of mugwort along sidewalks, backyards, parking lots and roadways where we’ve disturbed the earth. It’s related to absinthe and sagebush (not the cooking herb known as “sage”).

USES: Ragweed is useful to non-humans. The oil-rich seeds are good bird food, particularly in winter. Mugwort and ragweed are used in homeopathic medicine. Mugwort, in particular, seems to have a number of useful herbal applications. For example, it’s recommended as an herb for a “sleep pillow” and it’s sold as a lice and mite repellant for caged birds.

Invasive, common-as-mud, allergy-causing mugwort is still sold in nurseries and on-line. The variegated “Oriental Limelight” highbred seems to be very popular. One of my fellow Master Gardener Interns spotted it in a Connecticut nursery this past week, at the amazing price of over $10 a pot. (I wonder what the hapless buyers thought when they later saw mounds of it growing wild by the parking lot!)




Here’s a tale of two vines: a Great American and its Asian twin. The picture taken in a Stamford churchyard is of the foreign twin, escaped from someone’s garden and running wild on a privet hedge. It’s called sweet autumn clematis (clematis terniflora or clematis paniculata).

The American twin is virgin’s bower (Clematis virginiana) is a native clematis in the buttercup family. It ranges from Manitoba, Quebec and Nova Scotia south to at least Florida. (There’s a western variety Clematis ligusticifolia, with the Spanish name “yerba de chivat”, so technically we’ve got triplets). While most sources say that sweet autumn clematis is “Asian”, New Zealand claims it as a native, with the Maori name “puawhananga”.

Both vines grow rapidly to about 20′ and look wonderful draped over a fence or climbing up a tree. The bees, butterflies and other pollen gathering insects love the fragrant flowers; birds like to nest in the thick, tangled vines. The flowers are followed by attractive feathery seeds. Neither plant appears to have much forage or medical value. Since many clematis are high in poisonous alkaloids, this may also be true of virgin’s bower and sweet autumn clematis. Sweet autumn clematis is readily available for sale in local nurseries and via the Internet. Many garden experts recommend it.

The flowers look alike so the best way to tell the vines apart is by their leaves: the native plant has toothed leaves and the foreign one has round, smooth edged leaves.

Since it’s much harder to find a seller of the native plant, I suspect that the Asian plant is easier to propagate, like the Asian bittersweet. So is sweet autumn clematis a kudzu in the making? It has gotten loose and is said to found in the wild from Southern Connecticut to Florida and west to the Mississippi. I see it climbing over hedges and fences in Stamford urban areas. While it’s not high on the Canadian and USA invasive menace lists, it is starting to make a few, particularly in the Southeast.

BTW: there are many, many lovely highbred clematis vines that make great garden plants. They come in a wide range of colors and if you shop around you can find ones that bloom most of the summer and a great mixer with roses (that tend to quit in the heat). Most these “garden” clematis like their roots kept cool and moist in shade but must have their tops in good sun to produce flowers. They take a couple of years to get started but are worth the wait. To my knowledge, in the northern USA and Canadian, none are invasive; but in the South and West, a few varieties are listed as potential trouble makers.



I used to think that tropical-looking burdock would be great as the star in a garden of pest and drought resistant, edible, native and naturalized plants. Then I found out what happens when burdock gets out of control.


Common burdock: Burdock is a member of the composite (daisy) family, like its roadside companions, chicory and dandelions. There are at least three kinds of burdock present in North America, all Eurasian imports. The best know is the “common” or “lesser” burdock (Arctium minus), which is pictured in this article. Common burdock has flower stalks rising knee to shoulder height. Common burdock is reported to be found in all providences of Canada and all parts of the USA mainland except Florida and, perhaps, some areas near the Great Lakes. I believe that it has also found its way into Mexico.

Great and woolly burdock: Also naturalized are the great burdock (Arctium lappa), and the less-weedy woolly burdock (Arctium tomentosum). The great burdock has towering flower stalks up to an amazing 9 feet. You can tell great burdock from the “common” form by the size, and by the arrangement of the flowerheads. The great burdock‘s flowerheads are arranged in flat-topped clusters at the top of the stems. The woolly burdock has fleece on the outside of its flowerheads.

Japanese gobo: Lastly, in the vegetable garden and truck farm, there is gobo, the Japanese cultivated version of great burdock.


Growing conditions: Burdocks like sun or part shade, and any type of soil, as long as it is well-drained. Burdocks have long-tap roots that hold about half the biomass of the plant, up until flowering time, making the plants seriously drought resistant.

Burdock is a biannual. Under ideal conditions, burdocks are bi-annuals, forming a basal rosette (low circle) of leaves the first year, and then dying after they flower in their second summer. A 1994 University of Manitoba study by Norm C. Kenkel and Kelly Graham, however, indicates that if conditions aren’t ideal, common burdock will remain in its immature stage for up to 5 years. The flowers, of course, are followed by the notorious seed-burs.

Burdock spreads only by seed: The seeds are definitely spread via the hooked burs hitch-hiking on passing birds, humans, and furry critters. It may also be that birds eat and spread the seed. However, while there are innumerable reports of birds roosting on burdock, eating the seeds, and using the seed fluff for nesting, there are some reports that burdocks seeds may be poisonous to some birds. Further, while burdock pops up under bird-roosting places, I haven’t found any studies that confirm that the seeds are spread via bird-gut. It is said that it took common burdock some 200 to 300 years to spread to the West Coast, a slow creep which would be more likely if the seeds had to hitch-hike, rather than fly, at least most of the way.

Burdock needs infrequently distributed soil. Burdocks are normally found along roadsides, barnyards, fence lines and the like where the soil has been disturbed. The disturbed soil allows the burdock seeds to germinate and the seedlings to get a foothold. The period of disturbance has to then followed by a period of non-disturbance long enough for burdock to complete its multi-year cycle and make more seeds. Lastly, more disturbance is need for the new seeds to get going. Thus, burdock’s spread is inhibited by its need for once-in-while disturbed earth. Burdock can’t get established in undisturbed areas, in fields that are tilled every year or in areas that are mowed too frequently to allow the plant to flower.

Burdock as an isolated planting: Because of the special needs of a bi-annual that spreads only by seed, common burdock often occurs only as a isolated plant or two. When confined to isolated plantings, as it is usually is in the sub/urban environment, burdock “plays nicely with others” and is not in the same class as mugwort which crowds out almost everything in its path. In the ‘burbs, burdock is not generally as harmful to the environment as the sub/urban sprawl itself, and, in many ways, is just a part of the sprawl.

Burdock as a dominant species: Unfortunately, when conditions are ideal, common burdock also occurs in large patches. The University of Manitoba study was occasioned by common burdock becoming the “dominant understory species” in the Manitoba Delta Marsh area. I’ve been told that the area is open woods, with enough sun for burdock. (I wonder: what provided the necessary occasional disturbance of the earth? Could it have been the good ol’ white tail deer?)


Burdock is considered “low risk” by the poison centers, but tell that to human parents and animal caretakers. The burs can cause serious injury if they get in the eyes or are ingested (very rare). Mostly, they’re just very difficult to get out of hair and fur. (I once suffered a major haircut after crawling through a mess of them.)

Common burdock is a bird-killer!!! Now, here’s the bad part: there are several reports on the Internet of hikers finding the dead bodies of small birds such as goldfinches, kinglets, and hummingbirds that became trapped in burdock burs and then died of starvation and exposure. See an eyewitness report on the site of my colleague, Walter Muma.

When I first read about the bird-killing on Walter’s earthcaretaker.com site (thank you Walter for publishing this!), I was astounded. You can find innumerable pictures on the web of birds happily posing on burdock. I’ve known common burdock my whole life as a live-and-let-live neighbor, hair-snarling issues aside. Now, I find out it is a mobster. How? The best I can figure out is that, since all the bird-killing reports I’ve read came from hikers, the bird trapping tends to happen in the wild where burdock gets loose and grows densely enough that the burs can ensnare the little guys. If any reader has better explanation, please let me know as I can add to this article.

After this article was written, the following was received from noted ornithologist, Todd Jason Underwood, who has studied the issue:

“Regarding your question about where entanglements occur, from my observations, they seem to occur where there are large concentrations of burdock plants. I have only found one or two birds (out of about 30) entangled where there are isolated plants. Entanglements also appear more common where birds are concentrated during migration as most entanglements occur during fall migration. Another important thing to note is that burdock entanglement occurs with other animals as well. Insects are commonly caught as well as bats. I even found a dead northern leopard frog hanging by its mouth from a burr.”




Pink smartweed and white fall asters share the October sun, at the edge of a parking lot, with a yellow butterfly. Native asters make great carefree garden plants for a sunny location where their tall status (3′ or more) can be accommodated (See issue 27). Smartweed (polygonum) on the other hand, is horrible.

Smartweed, with the folk name “smartass”, has a behavior problem. Taken out of context, the stuff is attractive but then so are house mice and Canadian geese. However, it’s hard to be grateful for the inch of guano that the no-longer-endangered Canadian geese leave in their wake. In turn, smartweed’s not so charming when you’ve pulled it up for the fifth time this month.

According to the Army Corps of Engineers (even they’re watching the stuff), “There are approximately 96 taxa of Polygonum in the United States, 29 of which are not native or their native range is problematical. ” Translated into English, this means that the problem has 96 variations, foreign and domestic. Further translated, 96 kinds means there’s some for everyone, regardless of growing zone; and it means that there are annuals, perennials, short ones (under 6″); tall ones (over 6′), pale ones, white ones, greenish ones, pink ones, spotted ones, underwater ones, and who knows what else. Smartweed is said to prefer damper sites and at least half-day sun but I find it everywhere except in the driest places. The USA Army notes that “dense colonies [of the water variety of smartweed] can impede water flow in irrigation ditches … and restrict recreational activities along shoreline areas.” That bad.

Smartweed is in the buckwheat family. Buckwheat itself is believed to have originated in China long, long ago. Unlike grains such as oats and wheat, buckwheats are not part of the grass family; they’re on their own. Buckwheat makes delicious pancakes, and the bees turn the pollen into prized honey. However, as the smartweeds go, there’s an Asian variety that’s used like cilantro, but our 96 varieties generally aren’t safe to for human consumption. Many birds, including endangered water fowl, insects, and mammals do enjoy a frequent smartweed snack. You’ll note that, in the above picture, the butterfly has chosen the smartweed over the normally delectable asters. Humans, including Europeans and Native Americans, do use the highly acidic smartweeds for internal and external medicine. In Mexico, it’s said that soaking in a smartweed bath relieves rheumatism.

Smartweed blooms from June to November, which gives it plenty of time to make lots of seeds for the birds and water to disperse. The stem joints have a knotted appearance that can lead to name confusion because smartweed’s cousin called “Japanese Knotweed” (Polygonum cuspidatum) is a menace of in its own right.

I don’t know how you get rid of the stuff. I’m not sure you can. Control might be more achievable. Like anything else, the more you pull it up and prevent it from going to seed, the better off you are. Ironically, an agro-conference on the use of “Round-Up Ready” crops (i.e immune to broadleaf herbicides) noted that repeated use of Round-Up increased the smartweed population. To me, anything that discourages use of chemicals, particularly on food that I eat, is good, so perhaps there’s a silver lining after all.




You came across a tree with long palm-like tropical leaves. What is it? In New England, it is mostly likely to be ailanthus, sumac, walnut or ash. Ailanthus (Ailanthus altissima), the Tree of Heaven, Asia, and Brooklyn is often considered by naturalists and homeowners alike to be a menace to society with little redeeming value for wildlife. In contrast, smooth sumac (Rhus glabra) and staghorn sumac (Rhus tyhina) are great native Americans, as useful to humans as to our smaller residents. The black walnut (Juglans nigra), another great American, is cultivated in the wild by squirrels who adore these tall, graceful hardwoods, perhaps even more than humans do. The ailanthus is from the Quassia family of tropical plants, the sumacs are cashew family, and the black walnut comes from the walnut family which includes hickories and pecans. Our wonderful native ash trees are olive family members so can be distinguished from the others by the oppositely arranged branches and leaf stalks.

The ailanthus, sumacs, ashes, and black walnut come from totally different families and backgrounds, but can you tell them apart? All have long, palm-like compound leaves but there are major differences in flower, fruit, bark, bud, and leaf shape. This article covers the ailanthus and the sumacs. The black walnut is the subject of Issue 149 (January 30, 2005). Some of the ash trees are pictured in Issue 138 (November 14, 2004)

AILANTHUS: Graceful, tropical-looking ailanthus is the tree that grows in Brooklyn, and just about everywhere else (including Africa and Australia). It is as much a part of the urban landscape as the Norway rat, the cockroach, and the feral cat. Ailanthus was featured in “A Tree Grows in Brooklyn” where this arboreal immigrant’s determination to survive and flourish despite all odds gave inspiration to immigrants of the human species. In Brooklyn, I once saw a ghostly ailanthus sapling growing out of the dirt floor in a lightless sub-basement. Ailanthus saplings waving from roof gutters and fire escapes are common inner-city sights.

As a long-time Brooklyn resident, I have a unreasonable fondness for my old neighbor, the “Tree of Heaven”, as it is known in its native China. In China, the mature trees are valued as ornamentals; and the tree is used for lumber, firewood, medicine, and silkworm farming. (The wood, by the way, is similar to ash in look and quality, and actually is quite useful.) Conversely, in Virginia, where it threatens new forests, ailanthus is known, appropriately, I think, as “stink-tree”.

Unfortunately, like many back-alley denizens, ailanthus is “armed and dangerous”. Ailanthus uses its wind- and water-borne winged seeds (“samaras”) to spread into surrounding neighborhoods. Once it gets established, it spreads into a grove by means of underground shoots. Ailanthus is a proven alleopath; it uses chemical warfare to control its turf. The chemicals it makes can ward off at least 70 other species that could compete with it for space.

Ailanthus, however, can not tolerate deep shade, so despite its chemical armaments, it can’t compete under the thick forest canopy. Instead, ailanthus tends to grow in the sub/urban environment where few trees can compete with ailanthus for ability to withstand urban pollution. Ailanthus can also out-compete native trees when the forest canopy has been disturbed by logging or fire, and it can gain a foot-hold at the forest’s edge by out-competing and poisoning other “pioneer” and edge-of-forest plants. According to the US Forest Service, in China, ailanthus only grows “in a densely populated area of China where no wild lands are left.” Chilling thought.

Ailanthus was first imported into North America, they say, in the 1700’s, and was widely planted in cities (on purpose!) because it was pollution-hardy. Today, ailanthus is found in this hemisphere, in Zones 4 to 8, from Argentina to Canada. In the USA, it is found everywhere except the really cold places such as Alaska, Idaho, the Dakotas, and Minnesota. Ailanthus is useful for ground stabilization in pollution-prone industrial sites but I doubt anyone has to take the time to plant it.

Ailanthus is a fast, fast growing tree that lives only 25 to 50 years but it can get very large – 60 to 100 feet–in that time. While the individual trees aren’t that long lived for trees, the ailanthus groves can sustain themselves for hundreds of years.

Most American wildlife hasn’t much use for the foreign-born ailanthus. Even white tail deer and grey squirrels aren’t partial to it. A couple of bugs of Asian origin, such as Japanese beetles, munch on it (and presumably provide some value to the ecology when the bugs are then munched in turn by birds and small animals). Honeybees (a European import themselves), though, do relish the pollen which makes quality honey after it has been aged.

Ailanthus is weedy and aggressive; it should be controlled for the sake of the environment. In particular, the female plants which send out the seeds should be kept cut to the ground. Further, the trees are not desirable around human dwellings. Larger trees can be a winter/wind hazard and the water-seeking roots have been known to interfere with sewer lines and wells. The roots are also said to give water an unpleasant taste. The males flowers have a strong odor often considered disagreeable (hence the name “stink-tree”). Ailanthus sap can cause dermatitis and the tree is a 9 out of 10 on the bad-for-allergies scale.