Sunday, May 29, 2011

Free Plants that Bite Back

People love to get free plants, and who would blame them?  Mother Nature does her fair of gifting us with free plants … you would not believe how many maple seedlings I pull up every year!  Some of these “gifts” are easily recognizable and dealt with in swift fashion.  But sometimes you get something NEW, and the gardener’s heart flutters in anticipation: “Oh look, something has arrived!  I’ll bet it’s something GOOD.”

Well, I hate to be the one to burst your bubble, but these days it is usually NOT something good.  Thanks to wildlife, wind, and water (the 3 main agents of dispersal), there are plenty of bad things arriving on a regular basis.  Some of these plants are so aggressive when mature that they will make you regret adopting them. Learn to recognize them early - before they bite the hand that feeds them!

A plant that is appearing now is one that is frequently mistaken for Orange Cosmos, but it’s Ragweed, Ambrosia artemisiifolia.  It’s wind-dispersed pollen is a major source of allergies in late summer/early fall, but seedlings are arriving now. Here’s a picture of a seedling in my neighborhood.

Ambrosia artemisiifolia
Microstegium vimineum

How about a soft and delicate looking grass that looks so pretty in the shade? Microstegium vimineum is a deceptively meek looking plant that will be all over your shade garden within a year if you let it go to seed.  Luckily it is easy to remove when it is young, and it is an annual so it won’t grow back if you pull it.  If you have too much already, use a weed whacker to keep it low until frost so that it can’t bloom and make seed.

Ligustrum sinense

Privet is a plant that is so ubiquitous that people think it is a native plant, but it is not.  Ligustrum sinense was imported to the U.S. from China in the 1800’s and now covers much of the “wild” roadsides.  You can find it as tiny new seedlings, young saplings, and even as multi-trunked trees in front yards.  Some people just call it “hedge” because that is what it is often used for.  It’s ability to set large number of seeds allows it to seed into areas and take over, out-competing what would have “naturally” grown there.  It is especially thuggish in wet areas, but it thrives in dry places too.  Learn to identify it:  note the oppositely arranged leaves, small white flowers, and dark blue berries on mature plants.  Remove it as soon as you can.

Chinese privet seedling

Here is a picture of it when it is just a seedling (and very easy to pull out).  Notice the leaves are in pairs and are just a little "wavy" on the margins.
Nandina domestica

Nandina domestica is a popular landscape plant that if often called Heavenly Bamboo.  While this plant can sucker a bit locally, the real nuisance comes from birds eating the berries and spreading the plant to new locations.  I have found it numerous times in the middle of my wooded area, and I’ve seen it on the side of rural roads (please don’t tell me that someone planted it there!).

Nandina flowers

Here is one that frequently is mistaken for a holly, but Mahonia bealei is actually a member of the Barberry family.  Long used by Southerners as a landscape plant (I was horrified to see Home Depot selling it recently), this plant also appears courtesy of the birds.  I pull out several babies a year; it is easy to spot when I am close to the ground pulling out other weeds.  Turn the leaf over and you’ll see that the back side of it is almost completely white.  This is easy to pull out as a seedling.

Mahonia bealei
Back of leaf

Japanese honeysuckle (Lonicera japonica) has the distinction of disturbing more habitat in the Southeastern U.S. than any other alien plant: ¾ of a million acres!  Unlike Kudzu, honeysuckle is not so very noticeable, especially in small amounts.  I’ve been pulling it for years out of my property, and I’m not done yet.  It is no longer in the trees, it’s not anywhere it can flower and make fruit, but it’s covering a lot of ground still in the woods.  Look for the yellow and white flowers, opposite leaves and sometimes the leaves have a bit of “lobing” as shown.

Lonicera japonica
Lobed leaves

Ailanthus altissima

Tree of Heaven (Ailanthus altissima) – let’s give this a more realistic name, how about “stinking sumac”?  This sneaky tree pops up in places and tries to convince people that it’s a Sumac (Rhus sp.) or a Walnut (Juglans sp.).  It has started to invade my subdivision, and I have seen it pop up in at least 4 yards now, including mine!  Look for the purplish color on the new leaves, the distinctive notch on the lower part of the leaflets, and the very stinky smell if you rub it or cut it.
Ailanthus altissima Seedling
Distinctive notch on leaflet

Elaeagnus pungens

Elaeagnus pungens is often called “Ugly Agnes” due to its unkempt form.  It throws out long whips that get tangled in other plants, allowing it to climb higher; I’ve seen it grow 20 feet high in a Leyland cypress that was behind it.  This is an evergreen shrub in the Atlanta area and the backs of the leaves are distinctively silver colored.  Fall flowers and thorns are also characteristics of this plant.

Paulownia tomentosa

Princess or Empress tree (Paulownia tomentosa) is no royalty in my book.  This plant grows fast and tall, quickly shading out its new neighbors.  Seeds are tiny and numerous, spreading by wind and water to adjacent properties.

Pyrus calleryana

 Bradford Pear (Pyrus calleryana ‘Bradford’) is more appropriately known as “ornamental pear” because its seedlings are not true to the parent (so they can’t be ‘Bradford’).  Formerly sterile parents are now cross-pollinating with their cousins, creating thousands of viable fruit per tree.  Seedlings are recognized by a noticeable notch on one of the leaves and reddish petioles (stems).  Those that grow into trees are often thorny, which is the true nature of pears.  Vacant lots and roadsides around Atlanta reveal the extent of these errant saplings when they bloom in the spring.

Perilla frutescens

Perilla frutescens is sometimes called Chinese basil, Shiso, or wild red basil.  It makes a lot of seeds and spreads rapidly.  If this appears in your yard, pull it quickly or at least make sure it does not go to seed.

So if some new plant shows up in your yard, take the cautious approach and get it identified sooner rather than later.  In the case of these plants (and a few others), you'll be glad you did.

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