Invasive plants


Every year at the UConn Home & Garden Education there are a few topic of interest that we get a lot of calls about. Several years ago we fielded a lot of calls about the drought situation in Connecticut that occupied many people’s thoughts in 2016. In fact, that encompassed two years as we started to feel the effects of it in 2015. On the tail end of the drought, and perhaps in part because of it, many parts of the state were visited with an infestation of gypsy moth caterpillars. When we have a wet spring the fungus Entomophaga maimaiga, a natural control of the gypsy moth caterpillar, can flourish. The fungus overwinters as spores in leaf litter and in the soil. It then reactivates in the spring when there is sufficient rainfall. Although we were receiving an adequate amount of rain by 2017 it happened to occur a bit late for the fungus to be fully effective against the voraciously feeding caterpillars. So the summers of 2016 and 2017 were dedicated to answering many questions about the gypsy moth caterpillars and the damage that they wreaked.

As those two events have wound down a new concern arose for many of our clients. Thanks in part to press releases and an interview that aired on NBC CT in June the giant hogweed, Heracleum mantegazzianum, (below images) jumped to the front of the queue. The Connecticut Invasive Plant Working Group (CIPWG) issued a warning about this invasive species which was first spotted in Connecticut in 2001. Most of the populations of giant hogweed are under control and none of the reported sightings in 2018 were positive.

There are many look-a-like plants and it is those species that we are asked to identify. Starting in early-June calls and emails began to come in to identify large herbaceous perennials that were striking fear into Connecticut residents. This is in part due to the pretty noxious nature of the giant hogweed sap. Within 24-48 hours after skin has been in contact with the sap painful blisters may appear in individuals that are sensitive to it. Three things need to be present for the reaction known as phytophotodermatitis to occur. First, direct contact between the skin and the sap. Second, the skin must be moist as from perspiration, for example. Third, the contaminated area must be exposed to sunlight. If you are working in an area that contains giant hogweed it is easy to imagine that all of the criteria could be easily met.

Before attempting to remove giant hogweed from an area the first step should be positively identifying it. As I mentioned earlier, there have not been any confirmed sightings in Connecticut yet this year. It may be that the suspected plant is one of the following instead.

The first plant that is most commonly mistaken for giant hogweed is fellow member of the Heracleum genus: cow parsnip, Heracleum maximum, (images below). Unlike giant hogweed which was introduced to the United States 100 years ago from the Caucasus region of Central Asia, cow parsnip is native to North America. A tall herbaceous perennial that can reach up to 10 feet in the shade, nowhere near the 18 feet possible height of the giant hogweed, cow parsnip bears its flowers in in the flat-topped or rounded umbels that are characteristic of other members of the carrot family, Apiacea. Both species have compound deeply-lobed, toothed leaves but the cow parsnip lacks the red veining and leaf stalks common to giant hogweed. Cow parsnip also contains chemicals that cause phytophotodermatitis.

The next most common look-a-like is angelica, (below images). A first cousin once-removed, it shares its family, Apiaceae, with the giant hogweed and cow parsnip but is in the genus Angelica. Angelica grows 3-9 feet tall and also has large umbel flower heads. The compound leaves of angelica are what distinguish it from giant hogweed as they are bipinnate, meaning that they are compound leaves in which the leaflets are also compound (think honey locust leaves). Often used as a medicinal herb, angelica is the least toxic of the hogweed look-a-likes although it may still cause a skin reaction.

Queen Anne’s lace, Daucus carota, (below images) takes compound leaves one step further to tripinnate, having pinnately compound leaves that are bipinnate. The more levels of pinnation, the more delicate the overall effect. The airy-looking leaves of D. carota are what give it the ‘lace’ part of its name and are similar to its subspecies, the domestic carrot. Queen Anne’s lace has an umbellate flower head atop a much slimmer stem than giant hogweed, cow parsnip, or angelica. The sap from the leaves and stems can cause a phytophotodermatitis reaction although the flowers are used to make jelly similar to the yarrow jelly from our June 26th blog post.

The native Lactuca species includes wild lettuce (Lactuca Canadensis),

prickly lettuce (L. serriola), hairy lettuce (L. hirsute), and the blue lettuces (l. biennis, L. floridana, L. pulchella, L. villosa).

These tall plants start out from a basal rosette of leaves and can grow to 7 feet tall with large alternating broad leaves.  They have pale blue insignificant flowers compared to the dense clustered heads of the previous plants.

Finally, giant ragweed, Ambrosia trifida, has also made a plant identification appearance.  This 6-foot tall annual herb is a noxious weed that has become invasive in other parts of the world as it out competes native species in much the same way that the giant hogweed has here.

As plants and seeds have spread across the globe through human, animal, mechanical, or water means many species have landed in non-native locations and taken root there. If you are a fan of podcasts, check out the Infinite Monkey Cage’s Invasion episode where scientists and comedians take a look at the problems caused by alien (plant) invasions.

Susan Pelton, UConn Home & Garden Education Center

All images by CIPWG and UConn

 

 

catalpa flowers 6-25-18 Pamm Cooper photo

Flowers of the Catalpa tree

 “ Nature gives to every  time and season some beauties of its own

– Charles Dickens

After a cool, wet spring and a similar June, July came in like a jalapeno pepper and is staying that way for a while, at least. It is a good thing that our native plants are adaptable to the swings in both temperature and water availability fluctuations. I am also a native New England carbon-based anatomical wonder, but I have a more difficult time with excessive heat coupled with high humidity. The one good thing about this time of year, though, is the wealth of interesting flora and fauna that provide a little excitement, if that is what you need, as you venture outside.

Bittersweet and an old truck

Bittersweet growing through the cab of an abandoned truck

Some of the most spectacular caterpillars are works of progress at this time, and also in late summer and early fall. Daggers, sphinx and prominent caterpillars are always interesting finds for me. They get larger than spring-feeding caterpillars, and often have warts, knobs, hairs and colors that make them stand out. Furculas, for instance, are prominents that have anal prolegs that act more like tails. When disturbed, they flail them about and that action may drive predators away. Sphinx caterpillars usually have horns on the rear end and may get quite large before they pupate. Most are not pests, but beware of the tobacco hornworm if you grow tomatoes.

wavy lined heterocampa lookimg toward the sky Pamm Cooper copyrighted

A wavy-lined heteocampa, a prominent moth caterpillar, looking toward the sky

early instar blinded sphinx July 4 2018 Pamm Cooper photo

Very small blinded sphinx caterpillar

Most milkweeds bloom Between June and late July. This year common milkweed is almost done none in many areas. Soon the swamp milkweeds will bloom, though. Milkweeds are important sources of nectar and pollen for many bees, moths and butterflies, and many other insects feed on the foliage and flowers. Check any of the milkweeds, including native and non-native butterfly weed, for the monarch butterfly caterpillars.

fritillary and skippers 7-11-14 on swamp milkweed

Fritillary and skipper butterflies on swamp milkweed in July

Most birds have raised their first broods, and many are started a second one. pIleated woodpeckers may be seen directing their young to food sources. These include trees and logs in which carpenter ants are actively feeding. Although  pileateds are very large, if not for their raucous calls and loud drumming that give them away, they can be elusive to find unless you know where they live.

Pileated Case Mountain Pamm Cooper photo

Pileated woodpecker

Butterflies have not been as abundant as last year, especially the red admirals and painted ladies. Since these are migratory, one wonders if they were held up in the southern areas and now the second generation be arrive later on.  Hairstreaks and skippers also were few and far between, but now the summer ones are starting to put in an appearance. I was delighted and surprised to have a white admiral butterfly visit the flowers in my backyard gardens this week. In all the time I have spent in the outdoors, I have only ever seen three of these, and this one was a hybrid, likely a result of a red-spotted purple/white admiral matchup.

white admiral cross backyard bush honeysuckle 6-30-2018 IIPamm Cooper

White admiral hybrid

Some summer flowering trees like the exotic mimosa, or hardy silk tree, should bloom in July. We are glad to have one of these on the UConn Campus, just outside of the Wilbur Cross building. Its flowers are pink, fragrant and showy, and to my mind look like fluffs of cotton candy. Catalpa trees finish blooming in early July, dropping their white flowers to the ground like a summer snow.

hardy silk tree UConn Wilbur

Hardy silk tree, or Mimosa

Wildflowers that begin bloom in July include the Canada lily, Lilium canadense, and the wood lily. Both attract butterflies and are a striking hint of color among ferns and herbaceous plants in sunny areas. In the woods, look for Indian pipe, a surprising member of the blueberry family which has no chlorophyll. White in color, you can see how it got its nickname- the ghost plant.

indian pipe

Indian pipe

Canada Lily Lilium canadense 7-14-13

Canada lily Lilium canadense

Fawns are here, being carefully trained by their mothers to be sure to sample hostas, yews, phlox and other tasty garden plants. Knowing this behavior inspired me to put plants that the deer are known not to like, at least for this moment in time, on the edges of my garden beds. I tuck the plants they seem to like to nibble on far enough behind the plants they will not eat, that so far- three years now- they leave stuff alone.

When we get afternoon or early evening thunderstorms, remember to look for rainbows once the sun starts to shine again. If there is going to be a rainbow, it will appear where the storm is still passing through, but the sun has to be behind you.  We can get some great clouds any time of year, so don’t forget to look up now and then, especially in the early morning and late evening around sunset.

rainbow with faint double above

Rainbow over Bolton, Ct. July 3, 2018

Enjoy your time outdoors, even if it is time spent in your own backyard. You can see good and interesting things on nature shows and the weather channels, but it is far better to see it for yourself. The excitement never ends…

Pamm Cooper

feed me Pamm Coope rphoto

Don’t forget to stay cool!

According to the language of flowers, the rose belongs to the month of June symbolizing love and passion, gratitude and appreciation. Well I am passionately in love with and greatly appreciate all of June’s flower blooms, including roses.

Rose, red climbing-1

Roses can be found in home gardens, public gardens and even commercial parking lot plantings, usually as tough shrub rose varieties needing little care. Hartford is the proud location of Elizabeth Park, the oldest municipal rose garden in the United States established in 1904. Within its boundaries are beds and arches filled with hundreds of rose plants loving tended by professionals and volunteers, all taking pride in creating a beautiful and scent filled space for all to enjoy. http://elizabethparkct.org/gardens-and-grounds.html

 

Check rose plants carefully as gypsy moth caterpillars are feeding on leaves currently. Hand pick off and kill the little buggers by squishing or dropping in a container of soapy water. Signs they were there and left are shown by them leaving their shed exoskeleton after they molt.

gypsy moth caterpillars and rose

Gypsy moth on rose leaf, C.QuishPhoto

gypsymoth molted exoskeleton

Gypsy moth caterpillar shed exoskeletons. A sign gypsy moths were here. CQuish photo

Not all roses are a considered a ‘bed of roses’ or a good thing. The multiflora rose, Rosa multiflora, is an invasive species of rose, overtaking and displacing native plants. It was introduced to the U.S. from Asia in 1866 for use as rootstock and later widely planted as hedgerows and living fences.  Due to its very thorny nature, animals did not attempt to cross. Multiflora roses can be identified by its fringed petioles which differ from most other rose species. When in mass  blossom, the make the June air incredibly sweet.

Rose, multiflower, C.Quish

Fringed petiole of multiflora rose, C.Quishphoto

A few other fabulous flowers caught my eye and camera lens this month so far. Lunchtime walk on the Storrs campus I found an unusual shrub in front the Castleman building. False indigo, Amorpha fruticosa, was sporting spires of purple and orange flowers similar to butterfly bush. I had never seen it before, and after researching its identity, I am glad I haven’t as the CT Invasive Plant Working Group has it listed as ‘Potentially Invasive’. It seems well behaved in the restricted spot surrounded by buildings and pavement, but pretty still the same.

False indigo bush cquish

False indigo, CQuish photo

The perennial Helen Elizabeth Oriental poppy is a lighter pink, eschewing the brazen orange color of traditional oriental poppies. Helen Elizabeth is softer on the eyes and blooms a little bit later than the orange one.

 

Annual poppies are just beginning to bloom in my garden. If you let them go to seed and collect the seed once the pods go brown, dry and rattle, you will have an incredible amount of seed to save, share or spread the beauty in other areas.

 

Foxgloves, Digitalis sp, are shooting up their towers of flowers in different colors. Some species are biennial and others are perennial. The spots on the throats of the flowers are believed to be nectar guides showing the bees and other pollinators the way in to find the location of the nectar.

Visit local, independent garden centers and nurseries for unusual plants not found in the big box stores or chain centers. I found the annual Popcorn Plant, Cassia didymobotrya, whose leaves smell like buttered popcorn when stroked, at Tri-County Greenhouse on Rt. 44 in Storrs Mansfield. A treasure trove of unknown annuals and surprising perennials, and large variety of tomatoes and vegetables were all over the sales yard. I especially love the philosophy of the place hiring very capable people with intellectual disabilities along with some great horticulturists.

June also brings disease and insects to the garden. A few of the things we are seeing from submissions for diagnosis to our office are shown below. Azalea galls were sent in from South Windsor and are being reported around the state. The fungal disease, Exobasidium vaccinii, develops from an overwintering infected plant part of azalea leaf, twig or flower, and malforms the plant tissue into a curled and thickened gall.  As the gall ages it turns white releasing more spores to infect fresh tissue. Control should be to hand cut off and destroy galls before they turn white.

Azalea gall, b.zilinski 2

Azalea gall, B.Zilinski photo

Another sample image sent in were sweet birch leaves with bright red growths called Velvet Galls. These red patches are soft felt-like growths made by the plant in response to  to wall off the damage by a tiny eriophyid mite feeding on the leaves. The red patch is called an erinea. Unsightly while still being pretty, the damage is considered only cosmetic and causes no lasting harm to the tree. Thanks to Jean Laughman for her photos.

velvet gall on birch 2 Jean Laughman photo

velvet gall on birch,Jean Laughman photo, 6-8-18

Another great photo was sent in by Shawn Lappen for insect identification. The Dusky Birch Sawflies were striking a classic pose while eating the heck out of the leaves of a birch tree. Sawflies are stingless wasps whose larvae are plant feeders. The larvae are not caterpillars as this insect is not in the butterfly and moth order of Lepidoptera. Feeding damage usually does not cause much damage to a tree in good health. If control is needed, insecticidal soap will suffocate the larvae when sprayed on them.

Dusky Birch Sawfly, from Shawn Lappen

Golden tortoise beetles are attacking morning glory and sweet potato plants. They look like a little drop of gold but their beauty belies their destructive nature. Hand picking and dropping into a container of soapy water will kill them quickly.

Golden Tortoise beetle

Be on the lookout for Luna moths during the month of June. It is one of the largest silk moths and is attracted to lights at night. After mating, the female will lay her eggs on one of the host plants for the caterpillars including white birch (Betula papyrifera), persimmon (Diospyros virginiana), sweet gum (Liquidambar styraciflua), hickories (Carya), walnuts (Juglans), and sumacs (Rhus). The photo below was sent in to us last June 4 by A. Saalfrank.

Luna moth A.Saalfrankphoto 6-4-2017

Leave the light on to attract Luna Moths

-Carol Quish

It’s the very beginning of June in Connecticut.  Since mid May or so, gorgeous patches of pink, purple and white ‘wildflowers’ have appeared along roadsides.  A few years ago, my mom was visiting from Michigan around this time for a graduation.  She has been an avid gardener for many years and when she saw these flowers, she exclaimed, “oh, those wild phlox are just beautiful!”   So even a seasoned gardener can mistake this invasive plant, Dame’s rocket (Hesperis matronalis) for wild or garden phlox.

DamesRocket.GarlicMustardJAllen  J. Allen photo

Relatively speaking, Dame’s rocket (other common names include dame’s violet and mother-of-the-evening) is a newcomer to the status of invasive plant so its impacts on native species are not well studied.  It is known that it effectively forms monocultures where it has escaped from cultivation, is a prolific seed producer, and is not kept in check by pests or diseases in North America.  It is still readily available as seed commercially but is banned as an invasive in some states including Connecticut and Massachusetts. This means it cannot be bought, sold, cultivated or moved within these areas.   Unfortunately, it is still commonly included in ‘wildflower’ seed mixes for gardens in other parts of the United States.  According to a USDA distribution map, it is found throughout the continental U.S. except for the most southern parts and much of Canada.

Where did it come from?  It was introduced as an ornamental from Eurasia in the early 1600s so it’s had plenty of time to become established.  Dame’s rocket is in the plant family Brassicaceae so is related to the mustards, cabbage, broccoli, kale, etc.  The leaves, oil and seeds are edible and the plant is cultivated for its oil which is used in perfumes. Young leaves are a good source of vitamin C and they can be used in salads.  Speaking of perfume, it’s reported that the flowers of this plant produce a stronger scent in the evening.

DamesRocketLeavesJAllenDamesRocketFlowersJAllen J. Allen photos

Characteristics that can help identify Dame’s rocket include branched clusters of white, pink, and purple flowers that are about 3/4-1″ across and have four petals.  True phlox flowers have five petals. In addition, true phlox (wild) flower later in the season.  The leaves of Dame’s rocket are alternate, lance shaped and have serrated or toothed edges as shown above. In addition, leaves (except for the lowest on the stem) are directly attached to the stem and have no petioles. In contrast, true phlox have opposite leaves.  I’ll pop in a photo of true phlox below so you can see the leaves and flowers together.

 Wild blue or woodland phlox (Phlox divaricatahttps://en.wikipedia.org photo. This species is native to eastern North America.

Another distinctive feature of Dame’s rocket is the long, spindly seed pod (silique).  These form from the bottom of the flower cluster upward, so the youngest flowers (formed over a 4-6 week period) are at the tops and produce seed pods last.  Seeds and pods mature over the summer and when dry they split open releasing seeds into the soil.  Some are eaten by birds allowing for longer distance dispersal.  Each plant can produce hundreds of seeds which can remain viable in the soil for many years.

Dame’s rocket seed pods (siliques) on the left (Mark Frey, The Presidio Trust , Bugwood.org.  First year rosette on the right (Leslie J. Mehrhoff, University of Connecticut, Bugwood.org).

This plant is considered a biennial or short term perennial.  The first season of growth from seed produces a low-growing rosette of leaves which survive and remain green through the first winter.  The next season a 2-4′ flower stalk is produced as shown above.  This will dieback in the fall and some plants will produce new flower stalks in the third year.   The plant appears perennial where established in part due to the large seed supply that is produced annually.

It’s hard to want to destroy such a beautiful plant but if removal is required the methods include mechanical (pulling), burning, or herbicide applications (useful for large populations).  The best time to pull plants is in spring before seed pods mature.  Seeds can still ripen on plants pulled at this time using nutrients from the stems and leaves so for effective eradication, bag or burn the plants and remove them.  If not feasible, pile the plants in the center of the area where there is likely to be a lot of seed in the soil already.  The pile can be covered with black plastic to heat the pile and kill some of the plants.  A good approach for herbicide use is to apply to rosettes in early spring or fall to avoid injuring desirable plants nearby.  In early spring they will not have germinated yet.  Temperatures should be at or above 50 degrees Fahrenheit.

J. Allen

 

 

autumn-leaves-autumn-2016

Some red maples still had leaves late in the fall in 2016

 

“ November comes
And November goes,
With the last red berries
And the first white snows.”

– Clyde Watson

This fall was spectacular in its color displays both in the leaves and in the skies.And we are not done yet. A relatively indifferent  landscape can turn charming or spectacular when autumn colors abound as they have this year. Since a pictures is said  to be worth a thousand words, I will save you much reading…

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Canada geese on a pond splashed with early morning fall colors Pamm Cooper photo

american-lady-fall-2016-pamm-cooper-photo

American Lady butterflies migrate south for the winter, along with sulphurs, monarchs, cabbage whites and red admirals

delicata-squash

Delicata squash- one of the smaller winter squash varieties

old-house-with-bittersweet-and-japanese-maple-rte-154-november-13-2016-pamm-cooper-photo

Old house in the background with Oriental bittersweet on the left and an old Japanese maple on the right . Location is heading south from the Goodspeed Opera House on Rte 154

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Mushrooms on a dying sweet birch in early November 2016.

mourning-cloak

Mourning Cloaks overwinter as butterflies and may be seen flying about near or in the woods on warm winter days

japanese-barberry-covers-the-forest-floor-november-13-2016

It is obvious where the barberry is in these woods. Photo taken near the Gillette Castle State Park

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Honey bees are visiting mums and witch hazel this week, as well as any Montauk daisies that are still blooming

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November 6 2016 dawn over Glastonbury, Ct.

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Here is a good example of thinking ahead when planting. A sugar maple on the left and a Japanese maple on the right were probably planted over 30 years ago and are the perfect companions for great autumn color.

Take some little trips this season in our little state. There is still some good color out there, but it may not last much longer. And you may not have to go very far to get some great visual  compositions. Perhaps just as far as your own back yard.

Pamm Cooper                                          All photos by Pamm Cooper

 

 

I have a fondness for teasel (Dipsacus species) because it was common in the area where I grew up in southwestern Michigan.  Of course, I didn’t know then that it was invasive, or even what an invasive species was.  Now, on road trips between Connecticut and Michigan, I watch for the distinctive flower heads as we drive along.  I’ve never spotted teasel in Connecticut (or elsewhere in the northeast) but according to references I’ve checked, it does occur throughout the area.  There are two species that occur in the United States, D. fullonum (common teasel) and D. laciniatus (cut-leaved teasel).  Common teasel is, not surprisingly, the most common but cut-leaved teasel is described as more aggressive in its establishment and spread where it occurs. teasel-jallen J. Allen photo

If you’re not familiar with teasel, it is distinctive due to its coarsely spined flower heads, pictured above. The plants are herbaceous biennials.  During the first year of growth, a leaf rosette is formed.  In the second year, a tall (3-8 feet), prickly stem forms.  It branches at the top and forms egg-shaped flower heads.  Tiny flowers emerge first in a band around the center of the flower head and develop both up and down from there.  The prickly dried flower heads can be used as a comb and were widely used in the plants native range for combing, cleaning and raising the nap of fabrics, especially woolens (sample device pictured below from the Trowbridge Museum website). teasel-handfabricnap-trowbridge-museumThe root system has a substantial yellow tap root with fibrous secondary roots.  Seeds are attractive to birds and wildlife.  Where teasel is native (Europe, Eurasia and northern Africa), it is recommended for gardens both as an ornamental and as an attractant for birds (ie the European goldfinch) and wildlife.  The dried flower heads are sometimes used in the floriculture trade.

A fascinating attribute of teasel is that the plants are considered partially carnivorous. Carnivorous plants are those that are able to trap insects or other tiny animals and digest them or extract nutrients from them to use as a source of sustenance.  In the case of teasel, the leaves on the stem formed in the second season are fused where two opposite leaves meet on the stem. This forms a small ‘cup’ where rain water collects and tiny insects are caught there.  In a study done in the UK by Peter Shaw and Kyle Shackleton and published in 2011, it was shown that common teasel plants with dead fly larvae placed in the water in the ‘cup’ had a 30% greater seed set and seed biomass than plants with no larvae.  While the larvae did improve seed production, they did not see an increase in overall plant growth/biomass.

To distinguish between common and cut-leaved teasel, both the leaves and flower heads can be used. See the images below for comparison.

teasel-common-leaves-bugwoodteasel-common-flower-bugwood Common teasel leaves and flower heads.

teasel-cutleaved-bugwoodteasel-cutleaved-flower-bugwood Cut-leaved teasel leaves and flower heads.

All above photos from: ©Richard Old, XID Services Inc., Bugwood.org

The first report of common teasel in the U.S. was dates back to the 1700s but no additional reports are known until the 1800s when it was described in Oregon, Michigan, New York and Niagara Falls, Ontario. Since that time, it has spread and been confirmed throughout the contiguous states except in the northern great plains and the southeast.  Cut-leaved teasel was reported from Michigan and New York prior to 1900.  Both species are considered invasive in the U.S. but without a legal status.  While described as being ‘invasive’, states don’t necessarily have a legal status limiting the distribution of these plants. Connecticut does not.

Besides using the dried flower heads, root extract has historically been used to treat a variety of ailments including stomach upset, pain, inflammation, nervous system maladies, and most notably, and more recently, in the treatment of Lyme disease. It is reputed to draw the bacterial pathogen causing Lyme disease out of tissues where it is protected from antibiotics into the blood stream where it is susceptible to them and to the body’s immune system. This is NOT a recommendation to use teasel in the treatment of Lyme disease in the absence of treatment by a medical professional.

J. Allen

 

Masses of white flowers are a common and beautiful sight along Connecticut’s roadways and in fields this time of year (late May through June). While there are (of course) many shrubs and trees bearing white flowers, one of the most predominant is multiflora rose (Rosa multiflora).   This rose is native to Japan, Korea and parts of China and has become invasive throughout eastern North America.  While it is invasive and is a real problem, we’re sort of stuck with it overall so go ahead and enjoy the gorgeous blooms.MultifloraRoseBush.JAllen  Photo: J. Allen, UConn

Multiflora rose was first introduced into the U.S. as early as 1866 for use as a rootstock for ornamental roses. In the 1930s, the U.S. Soil Conservation Service began to recommend it for erosion control and as a ‘living fence’ for livestock.  In the 1960s plants were even distributed to landowners for free to encourage planting as cover for wildlife including birds and rabbits and as a food source for songbirds.  Thanks to the songbirds, many seeds have been distributed to new sites because they do like to eat the nutritious rose hips (fruit).   The plant is now considered a noxious or invasive weed in many states including in Connecticut “…prohibited from importation, movement, sale, purchase, transplanting, cultivation and distribution under CT General Statutes §22a-381d”.

MultifloraRoseflowers.J Photo: J. Allen, UConn

It’s pretty easy to recognize multiflora rose when it’s in flower but also once the bloom period is over. Flowers are borne in clusters of mostly white but sometimes slightly pink flowers that are ½ to 1” across and have five petals.  Leaves, too, are distinctive.   They are alternate and compound, having 5-11 oval leaflets with toothed margins.  The base or petiole of the leaf is fringed.  Even the thorns are unique to this species.  They are large, curved backwards and have an oval base.  If a thorn is removed, it will leave a visible oval scar on the stem.  They’re pretty serious thorns and are reported to be capable of puncturing tires and leaving a painful gash in skin.  Overall, this plant can reach a height of about 15’ with long, arching stems.  It can also be a climber and at times you will see it spreading up against other vegetation or structures.  For some great info and photos of the thorns, fringed petals (stipules), and more check out this web page: http://na.fs.fed.us/spfo/invasiveplants/factsheets/pdf/multiflora-rose.pdf

MultifloraRosespreading.J.AllenMultiflora rose spreading through a natural area and up another tree in the background. Photo: J. Allen, UConn.

Reproduction is by seeds (prolific at 500,000 to a million seeds per large bush per year), suckers and by rooting at the end of stems that arch over and touch the ground. Widespread dispersal is via birds that eat the fruit and expel the seeds.  It’s reported that seeds which have passed through a bird’s digestive system germinate more readily.  Invasiveness is enhanced by not only the huge potential for seed production but also by the fact that the seeds can remain viable in the soil for up to 20 years.

Like other roses, the hips and other plant parts (leaves and flowers) are edible. The hips are high in Vitamin C, carotene and essential fatty acids.  It’s recommended to harvest after the first frost when berries are softened and sweet.  They can be eaten raw but do contain some hairs between the flesh and the seed that can cause irritation.   Leaves, flowers and hips can be used to make tea.  To make rose hip tea, mash the fruits and steep in hot water.  Leaves are best when young as the hairs on the undersides can become stiffer and less palatable later in the season.

Some of the broader impacts of this plant, like other invasives, include displacement/replacement of native plants and the resulting impacts on habitat and food supply for native wildlife. Pasture lands are adversely affected when these thorny plants encroach and reduce forage area for livestock.  Even forestry operations are affected because of the impenetrable, thorny thickets that form, reducing access and making work difficult.  Multiflora rose can thrive in a wide range of habitats from open sunny sites to woodland edges.  It can survive on a range of soil types but is not found in extremely dry or wet sites.

Control methods used include physical or manual removal including mowing, digging, and prescribed fire. Chemical herbicides can be used as either a cut stem (fall) or foliar application.  Biological controls are not yet available.  A virus that causes rose rosette disease limits growth in some areas but that also affects ornamental roses.  An insect, the European rose chalcid, is being studied for potential use.

By J. Allen

 

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