Leafy  Spurge

Growth Habit: Perennial, erect, up to 3' tall, spreading by seed or creeping roots.

Leaves: Alternate, long, narrow, ¼" wide and 2" long, usually drooping.

Flowers: Inconspicuous, surrounded by large heart shaped floral leaves which turn yellow-green near maturity.


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Weeds of Concern

The following plants are concidered weeds of concern in Fremont County, as they are all, with the exception of wild licorice, non-native species and can be invasive under the right conditions.

Click on the picture or name of the plant to see more information about that plant, including control strategies.


Just a Pretty Plant, by Nancy Webber

People enjoy pretty plants. We landscape our homes and plant flowerbeds. The horticultural trade looks for new plants and hybrids to satisfy our desires. Many of these ornamental species come from other parts of the world. Thousands of plant species have been introduced over the last two hundred years. About 200 species are now considered to be invasive weeds.

Here in Wyoming, with our long cold winters and hot dry summers, we often times find it difficult to find ornamentals that grow well for us. It’s exciting when we find a beautiful plant that thrives in our harsh environment; it seems too good to be true.

Here is a look at six pretty plants, escaped ornamentals that are now problem invasive weeds.

Tamarisk is a large flowering shrub, also know as Salt Cedar. The “ornamental plant” has a small, pink flower in finger-like clusters. Its green leaves are slender, very similar to evergreen shrubs. There are a number of beautiful examples of this plant around Lander and Riverton. Unfortunately This pretty shrub has escaped the gardens and can be found growing wild on reservoirs, along streams, canals, and in the river bottoms. The large plants of Salt cedar can transpire well over 200 gallons of water each day and will often dry up ponds and streams. As this plant drops its leaves every fall it deposits salts on the soil surface making its local environment even harsher to other species. With the hot, dry summers and the increased damage of the drought to the state this “ornamental plant” is one we need to live without.

Dalmatian Toadflax and Yellow Toadflax are examples of weedy ornamentals that have escaped the flowerbed, this time to invade rangeland. These plants are in the same plant family as snapdragons, Yellow Toadflax also being known as Butter and Eggs. The Toadflaxes are very hardy and thrive under dry conditions. Once established it is very difficult to control, repelling herbicides with it’s waxy leaves and resisting hand pulling with its underground stems. Dalmatian Toadflax has escaped from flowerbeds and cemetery plantings to infest areas around the Cemetery and Golf Course in Lander as well as up the Squaw Creek drainage west of Lander. Though toadflax is a designated noxious weed in the state of Wyoming, it can sometimes be found in wildflower seed mixes and needs to be watched for in those types of plantings.

There are many other examples of ornamental plants that have left the yard and garden to cause problems elsewhere. Purple loosestrife has moved from perennial flowerbeds to invaded wetlands habitats in many areas of the nation, including areas with climates much like ours. Many consider this lovely plant the most environmentally damaging plant that we have in the temperate regions of North America. It is not yet established in our area and we need to be careful not to introduce this problem into Fremont County’s valuable riparian areas.

The Daisy is one of America’s favorite flowers, and there are a number of beautiful native daisies. Oxeye Daisy is a lovely example of a non-native flower that has escaped from the garden. This plant can survive over a wide range of environmental conditions and habitats including grassland, overgrazed pastures, meadows and roadsides. This pretty but noxious weed has already escaped from contaminated hay to invade and dominate a riparian area along the Wiggins Fork north of Dubois.

Common tansy is a European plant introduced for its ornamental and medical properties. This aromatic plant grows 1 to six feet tall, it has deeply cut, fern-like leaves and yellow button-like flower heads. Common tansy can be seen in many yards and gardens around Fremont County and has escaped into otherwise pristine riparian areas throughout the County.

The Russian olive may be the best example of a good plant gone bad. In some surrounding states and a number of Wyoming counties this tree is considered a noxious weed and can no longer be sold or planted. We love this plant because it is hardy, has fragrant blooms and grows under less than perfect conditions (almost anywhere). It is fast growing, attractive and works well in reclamation projects and wind breaks. These characteristics make this tree/weed such a problem. It grows almost anywhere, produces massive amounts of seed, which is spread far and wide by birds out competing and replacing important native species.

These plants invade otherwise healthy ecosystems and over time replace the native vegetation. While they may be easy to look at, these monotypic stands eliminate the food base for many other organisms ultimately reducing species diversity and richness. The second most significant threat to endangered species, next to habitat loss from development, comes from invasive species.

Watch out for plants that seem too good to be true. Truly more trouble than they are worth.

Home owners are encouraged to plant species that are proven safe and to replace those which have a potential to escape.

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