Mimosa, Beautiful and Evil

As I walked across our pasture with the dogs this week, a soft scent took me back to childhood, when my favorite tree was the Mimosa.  Mimosas (Albizia julibrissin) are dwarf but fast-growing trees that branch near the bottom, making them perfect for young children to climb. They have a short life span (10 to 20 years, max). I can remember howling when my parents cut the backyard specimen to the ground and quoted Poe’s Raven, “Nevermore.”

Mimosas seem magical. Their pink puffball blooms smell faintly of baby powder and remind one of a ballerina’s tutu. The lacy compound leaves fold up when touched, as a reaction to changes in stem pressure. The magic ends when the blooms drop, leaving behind numerous bean-like seed pods. The unsightly pods remain even after leaves drop in the fall. Herein lies the problem. Those pods contain numerous seeds, all guaranteed to germinate. Everywhere. This nasty habit far exceeds the benefit of a tree that will thrive in heat, drought, and any type of soil. This is one of the first plants to colonize clear-cut fields in the southeast.

Southern Living Magazine’s Steve Bender (also known as The Grumpy Gardener) answered a reader who inquired as to the proper time to prune Mimosa: “Any time you can find a chainsaw.” Click here to read his diatribe against the species. NC State University recommends, “Cut down large trees with a chainsaw and treat outer two inches of cut surface of stump with undiluted glyphosate concentrate (53.8% is preferable).” Click here to read the full article. 

Mimosa is considered an exotic, invasive species. Around a decade ago, a cultivar with burgundy-chocolate leaves came into the trade. It was immediately popular. Alas, those plants are nearing the end of their natural life, so gardeners who utilized them as focal points are now searching for replacements.

Consider using dogwood, redbud or buckeye as a well-behaved alternative.

A sweet fragrance and delicate foliage

A thicket of Mimosas alongside an untended frontage road. They are slowly displacing native species.

Say Buh-bye to Bradford Pears

Finally, finally  the Bradford pear trees are starting to shed their petals as tender leaves emerge. For the first time in several weeks, I can take a breath without suffering from the smell of stale laundry. Bradford pear (Pyrus calleryana ‘Bradford’) came into popularity about thirty years ago. The first year we were married, my husband and I planted a row of them. That was before we knew about their associated problems: stinky blooms, messy fruit, weak wood and invasiveness.

At first glance, it seemed like a perfect choice. Nice white blooms in the spring and pretty red fall color. A rapid grower, its mature size was listed as a manageable 40 feet tall with a 20 foot spread – ideal for the home landscape. Within a few years, we encountered problems with fire blight (made the ends of the branches look like they had been burned) and entomosporium leaf spot. Everyone has a different sense of what smells good and what does not. Most people agree that Bradfords fall into the “does not” category.

If the smell does not offend your nose and your trees have been spared the ravages of disease, you should still be concerned about their tendency to split. The side limbs are attached to the trunk with a sharp acute angle (“narrow crotch” is a common term) and split easily. Once a mature tree has lost a large limb, it is impossible to make it look rounded again. Save yourself from an ugly view and remove a damaged tree entirely.

When initially introduced into the nursery trade, Bradford pears were sterile and thornless. They didn’t following family planning guidelines, however, and cross pollinated with other types of callery pears and produced copious amounts of fruit. The pears are tiny and, in and of themselves, do not offer a headache. Unfortunately, birds eat the fruit and spread seeds far and wide. These germinate into huge numbers of thorny wild pears.

An “invasive” plant is an introduced, non-native that spreads so readily that it displaces natives. Nandina and kudzu are typical examples. Each state has a list of plants that are invasive in that state. Always consult your state’s list before you purchase an unfamiliar tree, shrub or perennial.

If you should doubt that Bradford pear is invasive, take a look at the photo below, showing a hedge of them under power lines in rural countryside. These have been “planted” by birds.

The Arbor Day Foundation recommends red maple, Japanese Zelkova or Chinese Pistache as an alternative. Here in South Carolina, consider Redbud (Cercis Canadensis), Sourwood (Oxydendrum arboreum), Carolina Silverbell (Halesia carolina), and Chinese Dogwood (Cornus kousa). They are all excellent choices.

These trees are 17 years old. The pre-split limb separation is becoming visible at the top of the canopy. When the first tree split, we removed them all and replaced them with better selections.

A thicket of bird-planted Bradfords under a power line in the countryside.

Blooms look innocent but smell pee-yew.