Sunday, December 26, 2010

Winter Weeds

With most plants dormant here now, it is easy to spot evergreen plants.  Evergreen plants are a welcome sight in winter, offering a tangible sign of life in an otherwise dead-looking landscape.  Unfortunately, some of the most noticeable evergreen plants are invasive non-native plants.  We can use our ability to spot these plants to our advantage, however.  Now is a good time to find these plants and remove them from your landscape and on restoration projects.
Tsuga canadensis - a native evergreen
Here are six of the most prevalent invasives that are evergreen.  They are all woody plants and can be removed in at least two different ways.  If they are young and small, try pulling them out now while the ground is relatively moist (wear gloves to ensure good traction and minimize any reaction – English ivy can cause a rash).  If they are too large to pull, you can cut them and carefully apply (consider using a foam paintbrush) a bit of brush killer on the stump.  At the very least, remove any berries on the plant and mark the plants with some bright string or flagging tape (available at home improvement stores) so that you can come back to remove them properly in the spring.  Bag up any berries and place them in the trash.

Ligustrum sinense
The first plant is probably the most invasive plant in our area – it has disturbed more acres than any other plant and has naturalized so widely that some folks think it IS native.  Chinese privet (Ligustrum sinense) is known by many folks as “hedge” because it has been used for many years as a hedge plant. This plant has small leaves that are oppositely arranged on the stem and is considered to be a shrub or small tree. 

Chinese privet seedling

This plant is very adaptable and grows in both fairly dry areas and floodplains.  It spreads by berries (drupes) and by roots, often creating dense thickets.  The first few sets of true leaves on seedlings have a distinctly wavy look on the edges.  I usually find seedlings when I am bent over pulling out japanese honeysuckle.
Chinese privet thicket

Ligustrum japonicum

It’s cousin, Waxleaf ligustrum (Ligustrum japonicum) is becoming more invasive thanks to increased usage in landscape designs and availability in nurseries.  It has larger, more glossy leaves and very similar fruit.  This picture was taken in a wooded roadside where the plant has naturalized.  Shade tolerance has allowed all forms of Ligustrum to invade woodland natural areas like state parks; these parks are now forced to spend resources on eradicating it and to host “privet pull” workdays (a great way to donate some community service, by the way).

Lonicera japonica

Japanese honeysuckle (Lonicera japonica) has been a favorite of homeowners for generations because of its sweet smelling flowers and ease of cultivation.  Who among us has not pulled apart the white and yellow flowers to taste the sweet nectar? This rampant vine is capable of smothering less aggressive plants, shading out anything that might grow beneath it.  This picture was taken two houses away from me – the vine has grown twenty feet up the young pine trees and the base of it is now as wide as my wrist.  Evergreen leaves and pale flakey bark are key identifiers in winter; you may also see small dark blue berries.  If you look carefully, the leaves are arranged opposite one another although they may appear to be in whorls.

English ivy infestation

Another old-fashioned favorite gone bonkers is 
English ivy (Hedera helix).  Once prized in many a 
garden in Atlanta, it can now be found high in the 
tops of large trees throughout old, established 
neighborhoods.  The good intentions of many folks 
to “keep it contained” are not always kept, especially 
when properties change hands.  

English ivy seedling
An interesting fact about this non-native vine is that it only becomes mature enough to flower and set fruit (blue berries) when it is allowed to climb.  When kept confined to the ground, it remains in a juvenile form.  However, even there it is an aggressive and thick vine, shading out all that would try to grow underneath.  Many people that eradicate it report having native plants like Trillium and other spring ephemerals spring up once it is removed.  Watch out for early signs of infestation when neighboring properties have it in their trees – new plants are easily eradicated when they are young.

Mahonia bealei
Mahonia is often mistaken for a mutant holly plant, but it is a member of the barberry family.  Mahonia bealei is the aggressive European species that invades our wooded areas.  There is a species that is native to the Pacific Northwest which has the common name of “Oregon grapeholly”. A stout and prickly shrub, it has thick, shiny leaves, yellow winter flowers and bright blue drupes in the spring.  Someone once commented that a particularly large specimen on the side of the road looked like a “prehistoric” plant.  It was rather scary looking.

Nandina seedling
Bright red clusters of winter berries have earned Nandina a special place in the designs of winter decorations … and in the forests of the southeast!  Nandina domestica, also known as Heavenly bamboo, is a shrub with compound evergreen leaves.  A very invasive plant in Florida and south Georgia, the increasing warmth of the northern part of the state has allowed this plant to become more invasive in the last decade.  I regularly spot it now on roadsides and ditches as well as wooded areas.  Learn to spot those seedlings early so that you can pull them out while the pulling is still easy!

Elaeagnus (thorny)
Elaeagnus has the disreputable nickname of “Ugly Agnes” thanks to its rambunctious and untidy growth habit.  With regular sheering it can be a solid and substantial hedge shrub, but too often it is allowed to do what it wants.  Long whips of new growth allow it to grow almost vine-like into adjacent shrubs and trees.  My neighbors inherited these unruly shrubs when they bought the house 3 years ago; the previous neighbor spent hours keeping them trimmed.  The unsuspecting and overworked new owners ignored the shrubs … until their rampant growth toppled a mature Yaupon holly into the street.  I showed the homeowner how to cut the Elaeagnus away from the Yaupon, allowing it to spring back into a vertical growth position.  You can recognize Elaeagnus by its glossy green leaves with silver-colored backs, the intensely fragrant flowers and the bright red berries.  Some forms, like this seedling in my other neighbor’s yard, have thorns as well.  You can find this shrub along many interstate roads where it was planted for years by the Department of Transportation.

Interested in identifying other invasives? This is a good website – detailed photos for identification and links to learn more about methods of control for invasive plants in the Eastern United States.  Plants are listed both by common name and by scientific name – use your browser’s “Find” function to search for what you’re looking for (but be aware that the common name be not be the same as what you know it as, so search by scientific name if possible).

By the way, the first picture in the blog is a young eastern hemlock (Tsuga canadensis) growing in my yard.  We got snow on Christmas Day, and I took this picture then.  It’s not a weed!

1 comment:

  1. At the very least, remove any berries on the plant and mark the plants with some bright string or flagging tape (available at home improvement stores) so that you can come back to remove them properly in the spring. Bag up any berries and place them in the trash.evergreen shrubs