“Pretty” Purple Plants
Can be Pesky Plants
Many people will soon notice the pretty purple-flowered plants along roadsides,
in ditches and fields, especially in wet areas. But, that pretty plant can be
very invasive and damaging to other wetland plants, which can reduce the effectiveness,
diversity and ecological balance of the wetland area. The plant is purple loosestrife.
The pretty flowers eventually turn into enormous quantities of tiny seeds that
get spread throughout the wetland and create a seed bank that will last for years
to compete against desirable plants.
Purple loosestrife was introduced into North America in the 1800's
and into Illinois in the mid-1900's. It has only become a real
problem in the last 20 to 30 years.
The plants can become 4 to 6 feet tall and have massive root and stem systems.
High densities of purple loosestrife can create heavy mats that native wetland
plants cannot compete with effectively. The loss of native plants can eventually
mean the loss of native wildlife in the area and possibly even a reduction
in the natural ecological effectiveness of the wetland.
Many types of controls have been used, but mowing, weeding, burning
or using herbicides have not been effective on large scale areas
and may be too labor
intensive or costly. The problem is that the millions of seeds left in
the soil when plants are allowed to reproduce can send up new and
Researchers at the Illinois Natural History Survey in Champaign
are currently evaluating biological control of the weed through
the use of beetles that
are natural enemies to the plant. The method has shown to be effective
in many parts
of the state, at least in small infestations.
For individual landowners, the main consideration is to not encourage
and enable the spread of the plants. Do not move plants from one location
small patches early by cutting off flowers to eliminate seed heads
or other control methods. Monitor the spread of the plant in the
to the survey researchers. Do not purchase plants that may be suspected
to be purple loosestrife. The Illinois Natural History Survey loosestrife
June-July 2003: Herbs | "Pretty" Purple
Plants Can be Pesky Plants | Long
Term Planning Leads to Successful Gardening | Honey
Bees, Wasps and More | Rust Diseases
on Home Lawns