When non-native plants cause significant ecological or environmental harm, we consider them “invasive.”
Invasive species regularly appear in Top-5 lists of the most significant threats to biodiversity, along with habitat loss, climate change and pollution.
In the case of Bradford pear (as it is most popularly called, though we’re really talking about all cultivars of Callery pear–more on that later), its potential harm to ecology and environment is substantial.
Here are some reasons why MoIP is choosing to focus attention on Bradford pear this year:
1. They can displace native plant communities
When thinking about invasive plants from an ecological perspective, the most important aspect is how they displace native plants communities.
Native plant communities are important for a number of reasons. Plants native to a particular area have co-evolved with other plants and animal species that we love and that keep our ecosystems healthy.
Native plants provide food for caterpillars and other insects, that are in turn eaten by larger animals. Non-native plants do not share evolutionary history with other native species, and therefore are not as ecologically beneficial as native counterparts. (For more, read this article by Doug Tallamy.)
Because Bradford pears grow so quickly, they can form thickets in large areas of land just a few years after sprouting. And as with many non-native plants, it leafs out earlier than native species, which shades out spring wildflowers. This alters the natural light and micro-climate of the land around the pear trees. It limits the ability of native plants to re-establish themselves.
And this is important, because as E.O. Wilson says:
“I will argue that every scrap of biological diversity is priceless, to be learned and cherished, and never to be surrendered without a struggle.”
2. Without control, invasive ornamental pear trees are geared up to take over quickly
If different cultivars of Callery pears (including the Bradford pear) are grown in proximity, they can cross-pollinate and produce fertile seeds, carried by birds into new areas.
This fact sheet from the Missouri Department of Conservation says it well:
Callery pear is adapted to a wide variety of environmental conditions, including heavy clay soils, drought, heat and pollution. Growing best in full sun, it also tolerates partial shading. Spreading into open, disturbed habitats, naturalization occurs within early successional fields, parks, rights of way, power lines and other natural open areas. It grows rapidly, flowers at a young age, often develops thorns and produces large amounts of seed. It is also establishing in the understory of forests and woodlands and is able to flower and fruit in small canopy openings.
The seed bank and sprouting ability of Bradford pear persists for years after cutting or treatment, so further management is needed beyond the first treatment.
3. You can do something!
Plant native alternatives. The City of Columbia’s “Stop the Spread!” campaign suggests the following:
“…As these trees deteriorate or become unhealthy, they should be promptly removed to eliminate a source of pollen and seed.
The solution to this invasive issue ultimately lies in the hands of homeowners, landscapers and developers. Please consider one of the many non-invasive alternatives to Callery pear trees when undertaking new landscape projects or large community developments. A decrease in the number of Callery pear cultivars and hybrids would be beneficial for our entire community to potentially reduce power outages, save costs of trimming and tree removal, and create a more ecologically balanced community forest.”