Tag Archive | Invasive species

Acer platanoides ~ Norway Maple

Common Name: Norway mapleimage
Type: Tree
Family: Sapindaceae
Zone: 3 to 7
Height: 40′ – 50′ feet
Spread: 30′ – 50′ feet
Bloom Time: March to April
Bloom Description: Yellow-green in color
Sun: Full sun to part shade
Water: Medium
Form: Columnar to Oval
Suggested Use: Do not plant
Leaf: Colorful
Tolerate: Drought, Air Pollution


Dark green



50′ x 20′

‘Crimson Sentry’




35′ x 25′


Red in spring, bronze green in summer

Bronze, yellow


60′ x 60′

Emerald Lustre

Dark glossy green


Round, oval

60′ x 60′

‘Crimson King’




35′ x 35′

Princeton Gold

Golden yellow



45′ x 40′

‘Royal Red’

Maroon, red, glossy



40′ x 25′


Green with white edge



60′ x 50′

imageJohn Bartram of Philadelphia was the first to bring the Norway maple from England to the U.S. in 1756 and soon it began appearing along streets and in parks.

As its name implies, this maple is native to Norway and much of Europe into western Asia. It was introduced to the U.S. in colonial times as an urban street tree and is still widely used for that purpose today. Many years of horticultural selection has produced cultivars that vary widely in form, from columnar to densely global and different leaf colors varying from red maroons, bright yellow and even variegated. Many times the purple leaved varieties are miss identified as ‘red maples’. An easy way to identify Norway maples would be to break a leaf off and if the sap is milky, its a Norway. Other maples will have clear sap.

Norway maples are found in woodlands near cities, especially in the northeastern U.S., they have also escaped cultivation and invaded many forests, fields and other natural habitats. Norway Maple can be monoecious or dioecious, meaning it produces male (staminate) flowers and female (pistillate) flowers on either the same or separate trees. Either way, they produce a large quantity of seeds that germinate rapidly. The species can be locally dominant in forest stands, create dense shade and displace native trees, shrubs and herbs. Its dense canopy also can shade out native wildflowers.

The normal leaf color is a dark green but cultivars have also been created with maroon, purple, and variegated foliage. Leaf variegation is not a stable trait and often tree canopies will display solid leaves along with variegated. Few Norway Maples provide meaningful fall color, a few yellows at most and often persisting on the tree until late season frosts before turning a drab olive brown.image

Norway maples tend to have very shallow roots and sometimes growing grass or any other ornamental plant under it is impossible. This also is one dirty tree… dropping trash during every season; starting with flower buds, two crops of seeds, twigs, branches, and copious amounts of leaves. There are many alternatives to Norway maples.

Red maple – Acer rubrum

Sugar maple – Acer saccharum

Hackberry – Celtis occidentalis

Basswood – Tilia americana

Northern red oak – Quercus rubra

Sycamore – Platanus occidentalis

© Ilex – Midwestern Plant Girl

Pyrus calleryana ‘Glen’s Form’ ~ Chanticleer pear

Semen Tree

Another name for the Bradford Pear, and ornamental pear tree. Characterized by greenish-white flowers which smell like a cross between old semen, dirty vagina, and rotting fried shrimp. Common throughout the South, these trees are pleasantly located near eateries and other fine establishments.

“Oh darn, there goes my appetite, for the semen trees in front of the South Campus Dining Hall are in bloom.”

I love Urban Dictionary! It teaches me how to communicate with the yutes these days…


Common Name: Bradford pear, Chanticleer pear, Aristocrat pear, Cleveland Select pear.
Family: Rosaceae (Rose family)
Zone: 5 to 9
Height: 25′ to 35′ feet
Spread: 13′ to 16′ feet
Growth: Starts very upright and pyramidal, aging into an oval.
Bloom Time: April to May – before the leaves emerge
Bloom Description: White
Sun: Full sun
Water: Dry to medium – Can tolerate drought after established.
Tolerate: Clay Soil, Air Pollution
Salt Spray:  Moderately Tolerant
Soil Salt: Intolerant
Flower: Showy
Leaf: The leaves are alternate, simple, 2-3 in. (5.1-7.6 cm) long, petiolate, and shiny with wavy, slightly toothed margins. Good Fall
Fruit: Small (1/4″ / .5 cm), green bunches of fruit which are hard until softened by frost. After which, birds eat and disperse the seeds in their droppings.

Popular Cultivars and their differences:
Pyrus calleryana ‘Chanticleer’ (Chanticleer callery pear):
Narrower habit, foliage has a red-purple fall color.
Pyrus calleryana ‘Aristocrat’ (Aristocrat callery pear):
Leaves have a wavy edge, less prone to branch breaking, however more susceptible to disease, fall color is inconsistent.
Pyrus calleryana ‘Autumn Blaze’ (Autumn Blaze callery pear):
Good, early fall color, more cold hardy, susceptible to fire blight, consistent good red-purple fall color.
Pyrus calleryana ‘Redspire’ (Redspire callery pear):
Fall color more yellow than red, oval form, less prone to branch breakage, however very susceptible to fire blight.
Pyrus calleryana ‘Jack’ (Jack callery pear):
Shorter and more narrower than species, yellow in fall.
Pyrus calleryana ‘Bradford’ (Bradford pear):
Upright, fast growing, sterile cultivar. Fast-growing causes many branch failures, which can contribute to failure of the tree eventually.

imageI’m actually not particularly a fan of the pear, although I do love the true fruit kind. Pyrus communis ‘Williams pear’. I have a gnarly, old one, too tall to pick from in my yard. Occasionally, a squirrel will leave one on the ground and I’ll get to eat it.

Sadly, this ornamental tree is one of my boss’s favorites. We plant it in droves. Frowny face. He likes to line the driveways, flank patios and front doors with them. Yes, they are pretty, however there are many alternatives to white blooming, spring trees (Read Below) When these pears are in full bloom, many folks notice a foul smell. Even famed Horticulturist Dr. Michael Dirr calls the smell “malodorous”. Others have described the smell as rotting fish, chlorine or semen.

In 1858, a French missionary named, Joseph-Marie Callery (1810–1862), collected this plant in China and documented it’s existence. In the early 1900’s, the U.S. was having problems with their common fruiting pear (pyrus communis) succumbing to fireblight. In 1917, Callery pear seed was brought in from China aimed at developing a fireblight resistance for the species. It wasn’t until the 1950’s, that the Callery pear was perfected and marketed in U.S. as a promising, new ornamental tree, leading to monumental landscape plantings. During the 1980’s, concerns about its structural weaknesses and its escape into our native forests began to surface.

Callery pears are remarkably resistant to disease and blight, imagealthough they are regularly killed due to their naturally excessive growth rates causing them to be weak-limbed. Strong winds, ice storms and heavy snow are the chief culprits of pear deaths. Some cultivars, such as ‘Bradford’, are particularly susceptible to storm damage.

Many states now dealing with escaped invasive pears include Illinois, Tennessee, Alabama, Georgia and South Carolina. (Invasive.org is a great source for invasive species information in your area)

The reason they have become a problem in states like mine is the vast amount planted by landscapers and although folks think these pears are sterile, they really aren’t. In general, the various cultivars are unable to produce fertile seeds when they are self-pollinated, or even cross-pollinated with another tree of the same cultivar. However, if different cultivars of Callery pears are grown within an insect’s pollination distance (300′ ft – 100 m), they can produce fertile seeds, which birds will efficiently disperse. In addition to the previous method, fertile pear varieties are commonly used as the rootstock for grafting ornamental varieties. If the grafted crown is damaged, the fertile rootstock will grow out, producing fertile fruit. These two factors, among others, have contributed to the pear spreading into natural areas and becoming an invasive problem.

Here’s a list of wonderful alternatives to planting a pear:

Red horsechestnut ‎- Aesculus x carnea

Serviceberry – Amelanchier × grandiflora ‘Autumn Brilliance’

American hornbeam – Carpinus caroliniana

Redbud – Cercis canadensis ‘Alba’ (a white variety)

Yellowwood – Cladrastis kentukea

Dogwood – Cornus kousa, Cornus racemosa, Cornus alternifolia

Ironwood – Ostyra virginiana

Blackgum – Nyssa sylvatica

Chokecherry – Aronia melanocarpa

Blackhaw viburnum – Viburnum prunifolium

American fringetree – Chionanthus virginicus

© Ilex – Midwestern Plant Girl

Common Starling – Sturnus vulgaris


European Starlings were intentionally released by the American Acclimatization Society in 1890 because they wanted America to have all the birds that Shakespeare ever mentioned among other European birds. Every European Starling is a descent of the original 100 birds set loose in New York’s Central Park. Genetically, those from Virginia are practically indistinguishable from starlings in California. Today, more than 200 million European Starlings range from Alaska to Mexico, and many people consider them pests.

Starlings are related to the mynah bird and thus are great vocal mimics. Many can learn the calls of up to twenty different species. Birds whose songs starlings often copy include the American Robin, meadowlarks, Eastern Wood-Pewee, Killdeer, Northern Bobwhite, Wood Thrush, Red-tailed Hawk, Northern Flicker, and many others.

Starlings often participate in what is called a murmuration, where a huge flock shape-shifts in the sky as if it were one swirling mass. This is often caused by the presence of a predator and the flock’s movement is based on evasive maneuvers. There is safety in numbers, so starlings do not scatter, they move as an intelligent cloud, maneuvering from the hungry raptor, thousands of birds changing direction almost simultaneously. Scientists have been stumped as to how a bird, tens or hundreds of birds away from those nearest danger, sense the shift and move in unison?

Giorgio Parisi, a theoretical physicist with the University of Rome, published a paper about starling murmurations in the Proceedings of the National Academy of Sciences in 2010.

“The change in the behavioral state of one animal affects and is affected by that of all other animals in the group, no matter how large the group is. Scale-free correlations provide each animal with an effective perception range much larger than the direct interindividual interaction range, thus enhancing global response to perturbations.”

In 2012, Dr. Parisi published additional research showing that each bird is actually reacting to the birds nearest to it, that the movement is the result of a series of short-range reactions. With the 2010 study, the team looked at velocity; this time they studied orientation. Measuring how a change in direction by one bird affects those around it, the team discovered that one bird’s movement only affects its seven closest neighbors. So one bird influences its seven closest neighbors and each of those neighbors’ movements affect their closest seven neighbors and so on and so on. This is how the flock is able to look like a twisting, changing cloud with some parts moving in one direction at one speed and other parts moving completely opposite.

How Land Managers Deal with Invasive Species

Land managers need to learn and understand the problems associated with invasive species. Second to loss of environment, invasive species are the greatest threat to native species and native ecosystems. Invasives will crowd out natives that wildlife depends on, along with changing hydrology, and even soil erosion.

Land management teams need to know Best Management Practices (BMP) to help with the eradication of invasive species. Basic procedures including: an inventory, a plan, and neighboring collaboration, will greatly increase the chances of success.

Taking a plant inventory of the site is imperative. Mapping the information collected is the next step. Knowing exactly where the populations of invasives or natives are helps with future monitoring.  This can also predict the possibility of invasion from alien species and allow for prevention.

Reading the landscape and knowing key indicator plants, allows the land manager to know what type of area they’re trying to protect. This knowledge, combined with the inventory and maps helps the land manager execute a plan.

One of the best defenses against invasives is early detection and prevention.  After conducting the inventory, data collected will relate the natives to the invasives. Knowing what/where natives do exist on the site helps with decisions in how to obliterate the invaders.

The plan should include an Integrated Weed Management (IWM) technique. A land manager must decide a control method to match the specific situation of the location. Control methods can include; physical/mechanical, chemical, biological, or cultural.  The choice of procedure should  be considered in with the available time, funding, workers/volunteers, quality of area, and land use goals.

Collaboration with neighboring land managers helps increase the chances of removal of invasives. This is through sharing of information, combined techniques of control, and the monitoring of invasive species.

Some of the invasive species challenging land managers today are:

  • Alliaria petiolata (garlic mustard)
  • Phragmites australis
  • Lythrum salicaria (purple loosestrife)
  • Phalaris arundinacea (reed canary grass)

Discussion of the preferred control methods currently used by land mangers are as follows:

Garlic mustard can effectively be controlled by either an early spring or fall burn of adequate intensity.  A combination of spring burning, hand-pulling (do you know this plant is delicious?!? Try it in salads or Italian sauces) and cutting increases the success rate. A spot application of 2% glyphosate, in spring or fall when natives are still dormant, can be done via spray (consider over-spray), or by a soaked glove. Biological control may be met in the form of one or more of four weevils. Scientists are currently testing the potential of one of these Ceutorhynchus species as a control method. Ineffective methods include low-intensity fires that leave plants unburned.




Phragmites australis is one of the hardest invasives to control. The only effective method that is agreed upon is application of an herbicide with cutting.  Rodeo must be cautiously applied as it is non-selective and will kill grasses and broadleaf alike. Application should be done after tasseling as that’s when the plant is supplying it’s rhizome with nutrients. Cutting would take place at this time also, if being utilized. Great success has been had with large infestations where the quality was otherwise low (less risk of quality loss), with aerial spraying of Rodeo. Covering a stand with black plastic attached to ground can work for smaller groupings. Biological control, at this time, is inconclusive/unusable as scientist have not found any organisms or viruses that damages Phragmites. Burning doesn’t reach the rhizomes of this species, but may be used to remove the cut litter.  Disking or pulling could effectively increase the population if proper removal of the rhizomes isn’t conducted.


Purple Loosestrife

Purple Loosestrife has historically been controlled with the herbicide glyphosate, sprayed in late August. Scientists have discovered leaf-eating beetles in the Galerucella family that are an effective biological control. Hylobius transversovittatus, a root-mining weevil has also shown promise as a control. Mowing, burning, or flooding has proven to be ineffective, as it seems to just distribute the seed.

Reed Canary Grass


Land managers have varying positions on dealing with reed canary grass. Some argue it’s value as regenerative to ditchbanks and the difficulty in identification of the native form from the invasive species. Because of these opinions, if possible, a small stand of reed canary grass should be allowed to stay. Burning in spring and fall, chemical controls, cutting, disking/tilling, altering hydrology, and plowing in combination (2 or more) can successfully remove this invasive. There are no known biological controls.

Land management teams should understand the issues surrounding invasive species including; Alliaria petiolata (garlic mustard), Phragmites australis,  Lythrum salicaria (purple loosestrife), and Phalaris arundinacea (reed canary grass). Implementing BMP procedures, along with an inventory, a plan, and including neighborhood collaboration will ensure superior success.

© Ilex Farrell ~ Midwestern Plant Girl