The Ultimate Japanese Knotweed Guide
The following article was submitted by a website reader, Claire Mitchell.
The Ultimate Japanese Knotweed Guide
Leave a light on and an open window on a warm summer night in Virginia and you are likely to wake up to a see a stunning specimen resting on a wall or windowsill. Moths come in a myriad of subtle markings and colorizations, each a fascinating display of ways to blend in with nature.
Compared to our showy day-flying butterflies, moths tend to attract less notice for their beauty, often because we do not get the opportunity to study them closely unless they happen to alight next to an outdoor light or come inside at night.
It is difficult to determine the total number of moth species in the Commonwealth* but North Carolina lists 2666 species as of April 2014, far outnumbering the butterfly species for the state.
One of our most showy and easily identifiable moths is the lovely luna moth (Actias luna). They belong to the family Saturniidae and, like other large silk moths, have wingspans up to 4 ½ inches. Their wings are a pale green, allowing them to blend into summer tree foliage, and have long graceful tails.
Canada marks their farthest range where they typically produce only one generation per summer (referred to as univoltine), whereas in Virginia, they have two generations (bivoltine). In the deep South with longer summers, they may be trivoltine.
The caterpillars feed on a relatively diverse list of native trees including the following:
Despite this relatively wide range of host trees, it is a rare delight to see luna moths, particularly in the wild as they typically fly after midnight. The adults lack a mouth so do not feed. They are strong fliers and, once the adults find a mate, the female lays eggs that hatch in about one week. The caterpillars go through five instars, dropping to the leaf litter below the host tree and pupating, emerging as adults and the cycle begins again.
Some lepidopterists erect outdoor lighting systems with UV lights and white sheets to attract moths in order to admire their vast array of sizes, colors and body shapes.
We are fortunate to live in Virginia with such biodiversity, including the lovely and magical luna moth.
References and for more information:
If there is one plant guaranteed to wrap around the head of your weedeater and stop it cold, it is the long tough strands of yucca leaves (Yucca filamentosa). The plant has many redeeming qualities though and an interesting relationship with its one and only pollinator, the yucca moth (Tegticula maculata). In Virginia, the plant is just ending its annual bloom time so the yucca moth is likely visiting the sweet smelling blooms, transferring pollen and seeking choice blossoms to lay her eggs. She checks to see if any other females have visited the flower, and, if not, she lays an egg on the seeds which then become the food source for the caterpillars There are enough seeds to feed the babies so this symbiotic relationship works well for both plant and moth. After feeding, the caterpillars fall to the ground, burrow in and overwinter.
Yucca belong to the family Agavaceae, the same as agave which grows in Mexico. Indeed, the two look similar as they are both succulents and grow as rosettes their first year. They can flourish in arid conditions and withstand drought well. The yucca which is native to Virginia blooms every year and agave only blooms once, just prior to completing its life cycle.
For an unusual and dramatic plant, the yucca can make a statement in the landscape with its sculptural quality. Though this spring and summer has been very rainy in Virginia, the yucca is a good standby for years that are drier.
The dappled woods of certain Eastern forests are home to an unusual little wildflower which has a very distinctive appearance: Twinleaf (Jeffersonia diphylla) graces rich bottom lands, often in proximity to limestone outcroppings.
With leaves that resemble the wings of delicate green butterflies, the plant grows in colonies similar to mayapple (Podophyllum peltatum) and blooms when it is about six to eight inches tall . To view its lovely white flowers, one has to be either very fortunate or plan carefully to view previously identified locations where the plant lives, as the flowers only bloom a few short days in the spring and the petals drop in the least spring rain or breeze. At first glance, it appears the plant has two leaves but they are actually one deeply divided leaf, creating distinctive spring foliage that does not resemble any other plant growing at the same time. The flower has been compared to bloodroot (Sanguinaria canandensis) which also has a white bloom but the foliage quickly distinguishes the two plants. After blooming, the plant continues to grow (up to 18 inches) and creates a small seed capsule with a lid that opens when the seeds mature. They also spread by underground rhizomes, hence the large groups which can occur in undisturbed forests.
The botanist Benjamin James Bartram named the plant in honor of his contemporary and friend Thomas Jefferson who reportedly appreciated the diminutive beauty of the plant; of course, Eastern woodland tribes (Cherokee to the south, Haudenosaunee to the north and the Virginia tribes and many others in between) were likely familiar with the plant long before Bartram or Jefferson came to admire it.
Medicinally, the Indigenous people likely knew of twinleaf's healing properties for rheumatism, hence one of its common names, "rheumatism root".
A lovely patch of Jeffersonia can be found at the Shenandoah River State Park in Bentonville, VA. They grow along the Bluebell Trail in a spot between the river and a small cliff about a half mile from the trail head.
The Virginia Native Plant Society honored Jeffersonia dyphylla as its 1999 plant of the year.
By Barnes Dr Thomas G, U.S. Fish and Wildlife Service - http://www.public-domain-image.com/public-domain-images-pictures-free-stock-photos/photography-studio-public-domain-images-pictures/close-up-of-white-blossom-twinleaf-flowers.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=24916257
To pick just three invasives is hard. Unfortunately, we have a lot of established nonnative invasive plants in Virginia and several emerging threats on the horizon. Each person would likely pick different top contenders based on their experiences and eradication efforts.
All invasive plants have a few characteristics in common: they are aggressive growers, they reproduce quickly, there are few to no native species that consume them to help keep them in check and they are well-suited to flourish in the environment into which they are introduced.
All things considered, my top three invasives of the plant kingdom include garlic mustard, oriental bittersweet and Japanese hops.
Of the three, garlic mustard (Alliaria petiolata) actually has one desirable quality that the other two lack; it is edible and delicious! Many a fine quiche can be created utilizing the abundant greens in the spring when they are young and tender. As they grow and particularly after they flower, they tend to get a very strong flavor and become bitter. At some lower elevations, the greens are appearing now so get ready to gather the harvest. Garlic mustard can be used in everything from spaghetti sauce to stir fries to being eaten as a cooked green, Southern style, with a healthy amount of butter and a splash of red wine vinegar. It also freezes very well after being blanched, supplying some nice handy greens in the freezer for future consumption after all the outdoor plants have passed their prime.
For those not familiar with oriental bittersweet (Celastrus orbicalatus), in a word, it is horrible. Like kudzu and English ivy, bittersweet uses it vining growth to climb trees, engulf abandoned buildings and smother everything it covers, including our valuable native plants. Vines are particularly vexing as they can topple established trees if they grow long enough to reach the canopy, weigh the tree down and weaken its structure to the point where powerful summer storms and high winds combine to speed its demise.
The reddish orange colored roots are just scary, growing like a vast underground spider web. Begin pulling it by hand and it will come up with moderate effort, but it will disturb the soil for a far distance from the main vine.
Don’t be fooled by its attractive berries. Yes, they are nice for fall decorations but toss that attractive wreath out into the backyard once it’s passed its prime and a landscape management problem is born.
Take care with eradication with Oriental bittersweet: there is also a native bittersweet in Virginia which looks very similar – American bittersweet (Celastrus scandens). One way to tell them apart is that C. orbicaluatus bears blunt thorns and produces berries along the entire stem whereas C. scandens only has berries at the tips of the vines.
The final species which tops the do-not-plant list is Japanese hops (Humilus japonicus). This one particularly favors riparian areas and, like bittersweet, climbs over everything in its path. It blankets the banks of the Shenandoah and Rapidan Rivers, has taken hold along many a tributary and continues to colonize rich native habitats. It is of particular concern as floods help distribute the seeds farther downstream from the original site.
Japanese hops have a nasty defense to discourage its removal: tiny briars line its stems and pulling it by hand without gloves and long sleeves is akin to rubbing course sandpaper rapidly and repeatedly over one’s bare skin.
The seeds also have briars, a clever distribution technique, as they get caught in a passing opossum’s fur or hitchhike on the coats of raccoons, beavers and other rivers' edge inhabitant to be spread to other locations.
So, at this moment, these three nasties hold top places on my invasives list. It is a fluid list though and could easily change if I encounter a particularly large patch of Japanese stilt grass or wavy leaf basketgrass, porcelain berry, mile-a-minute weed or any of the other pernicious invaders. These and other plants are having a significant and lasting effect upon our local ecosystems. As always, the take away is plant natives!
As many master naturalists know, the emerald ash borer (Agrilus plenipennis) has been decimating native ash (Fraxinus spp.) trees throughout Virginia for several years. Most ash are in stages of decline, some as dead standing timber, many already toppled by winds or chainsaws. These hazard trees are causing municipalities, state and federal landowners and private organizations and citizens millions of dollars a year to manage and remove.
The impact is not only financial but also ecological as ash trees frequently grow next to rivers, streams and ponds. Such trees help create a healthy riparian area as the foliage helps cool the water in the summer, twigs and leaves fall into the water and help provide habitat for aquatic life and the trees’ roots aid in preventing erosion.
The loss of this valuable native tree is a serious blow following the death of native hemlocks (Tsuga canadensis) which have been widely killed by the hemlock woolly adelgid and which grew in similar sites as ash along waterways.
The larvae of the beetle is the life stage which causes the damage by feeding inside the tree and disrupting the flow of water and nutrients. Depending on the overall health of the tree and climate conditions, the larvae can kill a tree within two or three years.
Emerald ash borer (EAB) is native to Asia and was first discovered in Michigan in 2002 and in Virginia in 2003 (Fairfax County) and again in 2008 (again, Fairfax County following eradication of the first outbreak).
EAB has now spread extensively to 31 states and into Canada. In fact, one of the easiest ways to recognize ash now is the “blonding” of the bark –where woodpeckers remove the bark in search of the larvae.
EAB has killed hundreds of millions of ash trees but there is a glimmer of hope: four parasitoid wasps from China have been released at test sites in Michigan which are showing promise of decreasing EAB populations.
At the recent 2018 Virginia Association of Forest Health Professionals conference, researcher Jian Duan provided a presentation on these wasps and explained that biological control can protect small ash trees and saplings and may help ash regeneration and recovery in the aftermath of EAB invasion but several questions remain: Will the parasitoid wasps spread on their own? How many releases will be needed to establish a healthy population of the wasps? Will different wasps be needed in different parts of the country?
More research is needed and is on-going by many state and federal agencies and universities but at least there is some hope that our beautiful native ash trees can regenerate following the damage by emerald ash borer.
Even though it doesn’t really feel like fall with this week’s highs in the upper 50s, one little pest knows the cold temps are on the way. The brown marmorated stinkbug (Halyomorpha halys) are finding any tiny entry into homes, planning to settle down for a long winter’s nap in your attic, kitchen cabinet, bedroom and any other location in your comfy house.
Their name stinkbug described their most distinctive quality, an odor most often compared to that of cilantro, which they freely emit when they are bothered.
They are not just annoying pests; they pose serious economic threat to agricultural crops, damaging many fruits and vegetables, particularly those with soft skins such as tomatoes, pears, apples, green beans and berries. They puncture the exterior with their proboscis to feed on the juices, damaging the exterior and causing rot on the interior.
BMSBs were introduced into Pennsylvania from Asia in 1998 – likely from pallets or shipping materials into ports - and have exploded in population, now in almost all 50 states. Some landowners have more trouble than others – windowsills and walls can appear like a scene from a horror movie for some unfortunate people while homes in relatively close proximity only attract a few of the pests.
A good vacuum can be a fairly good control for a quick and efficient way to get them outside. For those who appreciate a more hands-on approach, the bugzooka can be a satisfying tool. Natural predators have shown some promise in coming to our aid – in particular, the wheel bug (Arilus cristatus) which is prevalent in Virginia, is a predator to both stinkbug eggs and adults.
Wheel bugs (Arilus cristatus) are one of the most effective predators of stink bugs
A lot of people get creeped out by spiders. Some deep instinct directs us to react with surprise and pay attention when we see small, fast and erratically scooting creatures. Spiders are unnerving to some as they are the little solitary beings that dwell in dark corners, immobilize and consume their food while it is still living and sometimes attack and eat each other.
Fortunately, as naturalists, we realize spiders have great value in the ecosystem and when found indoors, we tend to reach for a container to escort them outside rather than immediately grab the insecticidal spray.
The vast majority of spiders in Virginia are completely harmless but black widows (Latrodectus mactans) are one species to treat with caution. Fortunately, they are shy and just want to be left alone. They tend to bite when mashed or squeezed but otherwise they want to live their quiet lives in webs created in rock walls, cement blocks, wood piles and other protected areas.
They are very easy to recognize, particularly the larger females with her shiny jet-black body and very long legs. To aid in identification, they have a signature red or orange hour glass symbol on their abdomen and tend to hang out upside down in their webs, warning others to not eat them – a warning heeded by most predators except for birds and preying mantis who relish them as a snack.
The male black widow is about half the size of the female, brown or gray with lighter stripes across his body. He does not pose health problems to humans since he doesn’t bite. The widows get their name from the occasional practice of the female devouring the male after mating.
The female creates a light tan, round egg mass which contains up to 400 babies. The young tend to hatch at the same time so they will be about the same size, preventing older, bigger spiderlings from eating their smaller brothers and sisters.
Prevention is the best way to not get bitten – wear gloves and don’t stick your hand in places you can’t see or check first. If bitten by a black widow, seek medical attention immediately. Death is not likely but swelling at the bite site, severe muscle aches, dizziness, sweating, headache, anxiety and nausea may result.
As with most things, a healthy respect allows for acceptable cohabitation as long as the black widows stay outside in areas not frequented by humans, particularly kids and elders. If found indoors, the choice of whether to escort outside (very carefully with proper protection) or to spray is up to the individual. Fortunately, black widows do not jump.
As summer winds down, we celebrate one of the brightest and most enduring of flowers – the sometimes humble, often spectacular sunflower. There are over 70 species of sunflowers and, in Virginia, about eight native species. The cultivars grace home gardens in shades of bright russet, orange, pink and lemon yellow, attracting pollinators when in bloom with their spectacular colors. A classic standby of early homesteads, the sunflower provided beauty and a healthy snack with their seeds following blooming. Many Lepidoptera use the leaves as food.
Birds relish them as well, particularly goldfinch who choose the varieties with smaller seeds to dine upon, leaving the huge Russian mammoth sunflowers to others.
Recently it has become very dry in Virginia, with scant rain for two weeks and temperatures in the mid to upper 80s. As zinnias and dahlias curl and crisp in the hot temperatures and dry conditions, many of our native species thrive. One late blooming sunflower, helianthus tuberosus, continues to bloom, providing valuable nectar for late-season pollinators.
Also known as Jerusalem artichoke or sunchoke, the roots of the this native sunflower grow deep, a necessity when supporting growth of up to 12’. The Latin name of tuberosus refers to the starchy potato-like nodes on the roots, favored by Native Americans from the Mohawk in the north to the Seminole in the south of Florida. Their natural range is as far west as Texas, so Kiowa and other tribes throughout the Midwest would have relished them as well. In Indigenous communities, there is a resurgence in growing and eating native foods and sunchoke is one such food that is receiving recognition for its nutritional and health benefits.
They are particularly good for those with diabetes as they do not spike blood-sugar levels as do potatoes. They can be cooked like potatoes - boiled, roasted, made into soups or thrown into stir fries at the last minute as their hard crunchiness is similar to water chestnuts.
Sunchokes are blooming now and can often be found along roadsides, in empty lots and next to rail roads. The roots can be harvested after first frost but will hold in the ground until late winter.
The early signs of fall can be seen in certain black gum and sassafras trees that already have leaves turning shades of red and crimson. The ironweed and cardinal flower are in bloom, adding splashes of color to meadows and streamsides. Goldenrod is just fading, its yellow blossoms still attracting pollinators.
There is one non-native plant that is also blooming, one that many landowners regard with disgust as this aggressive interloper spreads with abandon, particularly along streams and rivers – anywhere that is sunny and moist- including sections of parks, lawns and roadsides. As naturalists, we know the story all too well as it has unfortunately been repeated often in the landscape industry: an ornamental introduced due to some positive trait which escapes the confines of yards and gardens and grows into a menace for our native ecology.
Such is the case with Japanese knotweed (Fallopia japonica), first introduced from Japan in the late 1800s as an ornamental, valued for its profusion of small white flowers in the fall and its habit for colonizing quickly.
It resembles bamboo but is not related, instead belonging to the buckwheat family. It is currently found in 39 of the 50 United States and listed as an invasive in 16 of them, including Virginia. It has spread to Canada and is found in all provinces except Manitoba and Saskatchewan. The extensive land area in which Japanese knotweed can flourish is due to its amazing hardiness - it can survive in areas with winter temperatures as low as -31 degrees and flourishes in many types of soils with varying pH levels.
Its reputation as a noxious invasive is supported by its monster growth habit- with roots which can extend 10 feet down and spread up to 28 feet horizontally, it can get started by one small section of root being brought in with a delivery of mulch or hiding within the soil of a potted plant. It can be extremely difficult to eradicate once established.
In fact, it has become such a serious invader in the United Kingdom that property values are decreased and when trying to sell, landowners have to declare the presence of Japanese knotweed on their property and detail their ongoing eradication methods. Some properties may become unsalable due to the presence of the monster since it can crack cement walks and buckle asphalt, impacting building foundations.
We refer to one of our favorite foragers for guidance on the culinary uses of Japanese knotweed and sure enough, Euell Gibbons (1) recommends it as a versatile food. In the spring, the early shoots can be harvested when a foot or so high (before leaves begin to unroll), boiled for three to four minutes and enjoyed with a bit of butter and salt. If it is too tart, a small amount of sugar can be added.
He notes that the asparagus-like tips can be boiled or steamed, pureed with butter and salt (and a sprinkle of sugar) and served as a hot soup. Extending into the dessert realm, Japanese knotweed lends itself well to jams, sauces and pies. When cooked into a pie, the stems are a good substitute for rhubarb.
Now is the time to scout out the colonies of Japanese knotweed for spring foraging as they are at maximum height - six to ten feet tall - and are in full bloom. Good luck spying this noxious invasive and maybe helping to control it just a small amount by eating it!
Euell Gibbons, Stalking the Wild Asparagus, Field Guide Edition, David McKay Company, New York, 1962, p. 109.
One of Virginia's butterflies that seems like it should be much more abundant, based on its host tree which grows extensively, is the American Snout (Libytheana carinenta). This cute little fellow does not seem very common, but the hackberry tree (Celtis occidentalis) is quite widespread, growing in a variety of soil types and habitats. It is a delightful encounter to see the American Snout, aptly named for its long and prominent mouthparts or labial palpi. They are masters at mimicking other butterflies flight patterns - ' bouncing like satyrs one moment, gliding like checkerspots the next' as Jim Brock and Kenn Kauffman note in Field Guide to Butterflies of North American.
The snout has a distinctive leaf shape wing with the forewing squared off at the tip. When both wings are closed, the beautiful orange, white and black band is completely hidden, helping the snout blend in with leaves and other forest debris and avoid predators. To further blend in with foliage, the Snout will hold its palps and antennae downwards to resemble leaf petioles.
The hackberry tree is one of the easiest to identify by its bark. Covered in warty protuberances and growths that resemble popcorn, the hackberry is a nice shade tree that grows in well-drained soils in full sun, commonly in mixed deciduous forests.
It has been a nice spring and early summer for frogs and toads. A pair of Gray Treefrogs (Hyla versicolor) made their home behind the rain barrel on the porch and he has serenaded her for the last month. They earned the names Romeo and Juliet since she was first noticed on the window sill when he was hanging out below on the lower wall. About dusk, he begins his musical trills and chortles, even making soft noises that sound like laughter; after one particularly active evening of singing, they decided to take a romantic swim and were discovered floating happily in the water of the rain barrel.
The female chooses the male based on his call and breeding occurs between April and August.
According to A Guide to the Frogs and Toads of Virginia published by the Virginia Department of Game and Inland Fisheries (and which each ORMN is issued at the beginning of the training course), the Gray Treefrog is 1.25-2.4 inches in length and typically has a dark star-shaped pattern and many minute warts on a gray to light green background. However, it can also be almost solid color with very subtle markings in order to blend in to their environment.They have a light spot beneath the eye and the inner thighs are orange or yellow.
The Gray Treefrog lives through the winter by producing a type of antifreeze from glycol in the cells. The glycol turns into glucose which keeps the frog from freezing. Its breathing and heartbeat then stop until the temperature warms up again.
Harvesting garden potatoes has slowed to an archaeological pace in order to protect the small Eastern Spadefoot (Scaphiopus holbrookii) frog. The only tool which can safely be used is a small trowel but the safest technique is to slowly move the soil aside by hand and wait to hear the startled squeak when the frogs are uncovered. They are named for the tiny dark spade on their back feet which they use to move soil aside and create cool burrows underground. These little frogs (1.75-3 inches long) are explosive breeders and usually remain buried, only emerging from their burrows after heavy rains to breed. During periods of extensive drought, they encapsulate themselves in an underground mud chamber to prevent moisture loss.
It is worth the extra time it takes to dig the potatoes in exchange for the insect-control benefits the Spadefoot offers.
Virginia is home to 27 species of frogs. Courtship and egg laying differs between the species and occurs starting in late winter and extending into fall. Water is needed for most species, where eggs are deposited which turn into tadpoles (larvae) followed by metamorphosis into frogs.
Difference between frogs and toads:
Many guides cite the Pink Lady's Slipper (Cypripedium acaule) as common in eastern forests, however it is always a nice surprise to come across this lovely spring wildflower.
The Latin word acaule means 'stem less', referring to the leafless flower stem. The stem grows up from two basal leaves.
Lady's Slippers favor pine forests but is also found in deciduous forests which have acidic soils (pH 4-5). The blossoms are light pink to magenta and, occasionally, white. Another variety which is found in Virginia, Cypripedium parviflorum, looks similar but has a yellow blossom.
It takes many years for Pink Lady's Slippers to go from seed to mature plant and requires a specific fungal association.
Like all orchids, the seeds require this symbiotic relationship since the seeds do not contain carbohydrate stores like most seeds to sustain the newly germinated seedling. The threads of the fungus from the genus Rhizoctonia break open the seed pod and provide the plant with soil nutrients that it cannot access on its own.
Native Americans refer to the plant as "moccasin flower" and historically (and currently) use the root as medicine to treat nervousness, insomnia, low fever and a host of other ailments.
-Many of the wild spring greens are coming to the end of their harvestable time as the days are getting hotter and the plants are flowering and going to seed. At this point, many become very bitter and less palatable - though many health-conscious people believe bitter greens are especially packed with nutrition.
There is one wild green that is just now reaching peak gathering time at the lower elevations. Pokeweed (Phytolacca americana ) has now grown to the optimal six to eight inches and is just waiting to be sliced off at ground level, brought home and prepared for the dinner table. Care needs to be taken with poke, however, as it should only be gathered young (most guidebooks say no taller than eight inches) and needs to be boiled three times before eating.
Long- time connoisseurs of this fine green sometimes push these recommendations, gathering it when it is nearly a foot high and only boiling it twice. Too, some books say to only eat the leaves after boiling but for those who have been enjoying this green for years, it is common to throw the stem and leaves into the boiling water and consume both.
As with any wild-gotten food, it is best to gather it with someone whose expertise you trust and follow the recommended preparation guidelines until you know your digestive system is happy with the new addition.
The berries should not be eaten. Ever. They are poison. Interestingly the juice from the berries was used as ink by soldiers writing home during the war between the states and the words are still legible today.
Poke weed is one of the most delicious greens and, due to its size, can be gathered in quantity in a relatively short time once a good patch is located.
It makes super good quiche, can be thrown into stir-fries or casseroles and has a delicate enough flavor that it can be added to smoothies for extra nutrition. Basically, pokeweed can be used any recipe that calls for spinach - except raw salads.
It freezes in ziplock bags extremely well and can provide healthy greens throughout the winter.
Pokeweed us a perennial plant and has a massive taproot. Though maligned by gardeners when it comes up in landscape beds, pokeweed has many valuable aspects. With its deep root, it pulls up minerals deep in the soil, another beneficial aspect to eating it. It grows in fields, along roadsides and tends to appear in disturbed areas.