Three All Too Common Invasive Plant Species in Connecticut

Invasive species out-compete native plants.

Sometimes plants entice us to enjoy them with an abundance of flowers, brilliant colors or sweet fragrances. They use these lures to keep us from noticing the stealthy way they overtake more subtle but productive native species.  Several examples of this invasive style of growth are showing up in wooded areas and back yards this time of year.

 Garlic mustard (Alliaria petiolate)

Originally introduced from parts of Europe and Asia for food and medicinal purposes in the mid-1800s, this flowering plant has become extensively invasive in most parts of the US. It appears in early spring in the undergrowth of woodlands, forests, along roadways and anywhere there is a bare, moist or dry open area. Its presence overtakes many native plants.

Garlic Mustard

It is a biennial that takes 2 years to mature enough to produce flowers that provide seeds.  During its first year of growth seeds germinate while the low-growing plants develop rosettes of leaves that can be hard to identify as an invasive. Its distinguishing fragrance of garlic when the leaves are crushed makes it easy to identify. A stalk appears the second year with small, white 4-petaled flowers atop the stalk. By the end of May seed pods that are dark and 4-sided develop and may each contain 22 or more seeds. The plant dies back by the end of June and the seeds are dispersed by humans or wildlife. The two-year cycle of germination and seed production continues as the plant spreads into new areas. Some research suggests that garlic mustard prohibits the growth of other plants in nearby areas. Seeds can survive as long as 5 years in the soil.

Management requires long-term  persistence. Hand- pulling to remove roots before seeds develop can be effective for small infestations. Removing plants with flowers and/or seed heads should be bagged and disposed of in the trash,  not in wood piles or compost areas. Chemical control can be effective but must be repeated due to the presence of seeds surviving in the soil.

Honeysuckle (Lonicera spp.) 

Honeysuckle plants were likely introduced into North America as ornamentals from Asia beginning in the 1750s. Some varieties arrived through the 1800s, and as late as the mid-1900s some varieties were still sold for various purposes such as arboretum specimens, for soil erosion control and for wildlife cover and food. Some varieties are still sold in nursery centers in some states; they are all prohibited for sale in Connecticut. They have all escaped cultivation and the seeds are spread by birds and wildlife.

The Connecticut Invasive Plant Working Group lists 6 types of honeysuckle on the state’s list of invasive or potentially invasive non-native species. They include the vine Japanese honeysuckle (Lonicera japonica), and the shrubs Amur honeysuckle (L. maackii ), Morrow’s honeysuckle (L. morrowii), and Belle honeysuckle (L. x bella). These are all considered invasive. The two potentially invasive varieties include the shrubs Tatarian honeysuckle (L. tatarica) and Dwarf honeysuckle (L. xylosteum). Plants that appear on this list are prohibited from importation, movement, sale, purchase, transplanting, cultivation and distribution under CT General Statutes §22a-381d.

Morrow’s honeysuckle with flower buds in early spring

Honeysuckle shrubs are leggy, have an open form and range from 8-12 feet high. The vining variety can grow to 30 feet or more. Leaves typically are opposite, oblong and have smooth edges. The leaf upper and underside of some varieties are smooth, other varieties are hairy. Green berries appear in early spring. Small tubular flowers appear within the leaves in May and June and can be white, creamy, yellow or pink. Often several petals cluster to form a tube. If sliced open, stems on non-native varieties will have a brownish hollow center. Stems on native species will have a solid center. Depending on the species, berries can be orange to dark red and ripen in mid-summer until late fall.

Morrow’s honeysuckle blooming

True to their classification, these plants can form populations that out-compete and suppress the growth of native species.  They can deplete the habitat of moisture, nutrients and sunlight. In addition, the nutrients in the berries of invasive species are lower than native varieties. This requires birds to spend time eating large amounts of less nutritious food and could affect their migration.

While honeysuckle population numbers are low in an area, hand removal of seedlings or young plants is best before berries ripen and birds begin to spread them while feeding. Controlled application of herbicides might be required for areas of large infestation. A biological control is not known.

Native deciduous plants such as chokeberry (Aronia ssp.), spicebush (Lindera benzoin) and dogwood  (Cornus ssp.) will all provide food and cover for wildlife as alternatives to honeysuckle.

 Winged Euonymus  Euonymus alatus

Burning bush (Euonymus alatus), also known as winged euonymus, was introduced in the 1860s from Asia as an ornamental landscape plant. It is used extensively along roadsides, in parks and residential plantings and to beautify industrial parks all along the east coast and southern areas of the US.

Winged Euonymus

It is a multi-stemmed, branching shrub that usually grows 8-10 feet but when mature can grow to 20 ft. It is called “winged” because of the shape of its stems. Small, greenish flowers appear in spring, followed by a hard fruit which matures to a reddish purple in the fall. The leaves of the bush become a brilliant red, giving it the popular name “burning bush.”

It is on the Connecticut Invasive Plant Working Group list of invasive species but its sale is not prohibited. It produces hundreds of seeds annually which generate many seedlings under the parent plant as well as in areas removed from its parent, such as surrounding woodland areas and neighbors’ yards. It seeds are spread by wind and birds.

Its spread can be controlled manually, mechanically or chemically.

Jean Laughman

 

 

The Bermuda Invasion

In my blog of October 11, 2018, I shared images and some information on various flora that are found on Bermuda and promised to talk about some of the species that have become invasive. You may wonder why invasive species on Bermuda might be relevant to us in Connecticut. Islands as small as Bermuda or as large as Australia may have species that are unique to their location and that have fewer defenses against introduced plants, animals, fungi, or microorganisms. These places are great concentrated studies in the effects of introduced species.

We have seen many invasive species become hot topics as they moved from other parts of North America or even other places on the planet into non-native locations in the Northeast. The Connecticut Invasive Plant Working Group lists over 80 plants that are currently problems, some of which moved into our region in just the course of a decade. Transported wood that is infested with the Emerald ash borer or the Asian longhorned beetle has enabled these insects to move easily from state to state.

Japanese barberry image, UConn Plant Database, EAB image, CT DEEP

The isolated volcanic islands of Bermuda were not subject to invasive species for most of its history. There were only 165 species of vascular plants, 5 species of bats, a species of skink and another of turtle on the islands when Bermuda was discovered. Over the next several hundred years thousands of plant and animal species were brought by ships to the islands, sometimes intentionally but more often not. Some came as stowaways as seeds in hay or soils, on ocean currents, as insects in food stores, or in the bilge water of the ships themselves.

Bermuda cedar (Juniperus bermudiana), Bermuda maidenhead fern (Adiantum bellum)

Until Bermuda was visited by the first Europeans in 1505 there had been no human-related importing of flora or fauna to the archipelago so it is a great microcosm of the effects of species introduction. When settlers come to a new place the first thing that they attempt is to make it ‘home-like’. The introduction of rabbits to Australia in 1788 by British penal colonies. Within ten years they numbered in the millions and ate enough vegetation to cause widespread erosion issues.

Rabbit around a waterhole, image from 1938/Australian National Museum

One of the first species introduced to Bermuda were the pigs that were released on Bermuda in the late 16^th century. By the time a European settlement was established in the early 17^th century the pigs had become abundant and feral. You may wonder why pigs were released in the first place. It was because the islands were used a place to replenish food and water, kind of a 17^th century truck stop by ships. The pigs did untold damage to seabird and turtle breeding colonies.

Cockroaches, Periplaneta americana, came to Bermuda as egg cases in the bilges of a ship in 1621. Wireweed, Sida carpinifolia, was already a rampant invasive in 1669 when then-governor John Heydon was calling for tenants to pull it up by hand.

American cockroach (Periplaneta americana) egg case image

Many of the introduced species were brought in to control other species. The Jamaican anole, Anolis grahami, arrived in 1905 to control the Mediterranean fruit fly, Ceratitis capitata, and has since become naturalized. A beneficial introduction came in the form of honey bees, Apis mellifera. A beekeeping record dated May 25, 1617 stated that “The bees that you sent doe prosper very well.”. The Bermuda palmetto (Sabal bermudana), a native plant, is one of the main nectar sources for these bees. The giant Cane toad, Bufo marinus, an introduced species, was brought in to control garden pests but unfortunately consumes a lot of bees.

Honey bee, Bermuda palmetto, Cane toad

The Indian laurel, Ficus microcarpus, an ornamental garden tree was not considered an invasive species until the 1980s when a pollinating wasp was introduced to the island. Known as a strangler fig like its cousin the banyan, Ficus benghalensis, the Indian laurel can crack through walls and water tanks. It is a primary food source for the starling, an introduced species that does a lot of damage as they spread invasive seeds from the Brazilian pepper, Schinus terebinthifolia, the asparagus fern, Asparagus densiflorus, and the Indian laurel.

Indian laurel &  banyan trees

Casuarina, Casaurina equisetifolia, over-shades native plant species and causes soil erosion. It was introduced from Australia in the 1940s as a windbreak but no plants grow beneath it. Kudzu, Pueraria montana, is familiar to Connecticut gardeners as it is also on the Connecticut Invasive Plant Working Group list.

Casaurina & kudzu

With 23 of the top 100 invasive species in the world, Bermuda is still at risk of additional invasive species as most of their food and consumer goods are brought in by ship. Visitors or traveling Bermudians also bring plants, fruits, and seeds on to the islands. When you travel anywhere in the world and see warnings about bringing back fruits and plants or prohibitions against moving wood, visiting farms, or petting livestock it is for the good of all to heed that advice.

Susan Pelton

 

Giant Hogweed and Its Look-a-likes in Connecticut

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 26^th 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

 

 

 

Comfrey Out of Control

Comfrey flower, photo by C. Quish

Not all pretty flowering plants in small, four-inch pots siting on the nursery bench are as innocent as they appear. Beware the sneaky aggressor! About five years ago the delicate and rare clear blue color of the comfrey blossom, shyly wooed me into taking it home. What could one more plant hurt in the side garden abutting the wild side of the neighbor’s yard hurt? Well, it hurt plenty. I have been cursing the day I planted it.

Comfrey gone wild. photo by C.Quish

Comfrey spreads incredibly fast. It is a hardy perennial with a deep and extensive root system. And its seed drop and are spread to create new plants elsewhere. The neighbor loves it and encourages its spread which doesn’t help my eradication efforts on my side of the property line. I suppose it makes a better fence than wood and nails, and he enjoys the view.  The bees enjoy the flowers, too. Dozens of honey bees can be found busily entering flower after flower, not caring how close I get to almost petting them.

Bee feasting inside comfrey flower. photo, C.Quish

Comfrey is botanically known as Symphytum sp. and is a member of the borage family. The Latin name means ‘grow together’.  It was first brought to America with the English as a healing herb. I contains a high level of the chemical allantoin which aids in cell formation, healing. It also is reported to contain pyrrolizidine alkaloids, known to cause liver damage when taken internally in large amounts. The leaves can be crushed or bruised to be placed on external skin areas to heal wounds and broken bones. I only use the plant as an ornamental and to spread into the neighbors neglected ‘wild’ area.

Comfrey has a tap-root, growing about 18 inches deep in the soil. It does a great job of breaking up compacted ground, accessing the minerals and nutrients out of reach of shallower plant roots. For this reason, comfrey leaves are a great addition to the compost pile, as those deep-seated nutrients of the ground are now taken up by the roots to be stored in the comfrey leaves. Once the microbes in the compost pile break down the comfrey leaves into its basic chemical elements, the nutrients are released into the compost and made available for use by other plants. Just don’t put any of those spreading roots into the compost pile. Keep any seeds out of the compost also.

So heed those enticing words on the plant labels when the just mention the words, ‘fast grower’ or ‘spreading’. Sometimes they really mean it!

-Carol Quish