Purple Loostrife & SaltCedar – Noxious Weeds in the Outdoors

March 30, 2009 by  

Jim McAllister

Sportsman, are you aware of noxious weeds that can limit habitat in wetlands for wildlife. In the last 10 years, the state of North Dakota has had two noxious weeds move into our wetlands. They both can have devastating effects if not properly controlled. They are purple loosestrife and saltcedar.

Purple loosestrife has been in the state for a number of years as an ornamental plant. It is loved by gardeners across the country. What has happened is that the cultivars, the sterile variety, have crossed with wild variety. This plant is quite capable of replacing cattails and other vegetation on the waters edge of cattail swamps. And when it gets out of control, ducks will avoid areas infested with purple loosestrife

Purple loosestrife is a perennial forb introduced to North America from Eurasia and Africa. Wild infestations are associated with moist or marshy sites. The stems are erect (1.5 to 8 or more feet tall); four to six angled, and can be smooth or pubescent with few branches. Leaves are simple (0.75 to 4 inches long, 0.2 to 0.5 inches wide), entire, and can be opposite or whorled.

The most identifiable characteristic of purple loosestrife is the striking rose to purple colored flowers (Figure 4). The flowers are arranged on a spike, which can be a few inches to 3 feet long. The plant usually flowers from early July to mid-September in North Dakota.

The spread of purple loosestrife is primarily by seed, but the plant can also spread by vegetation from stem cuttings. Research at NDSU has shown that seed viability of purple loosestrife growing in North Dakota wetlands ranged from 50 to 100 percent. With approximately 2.7 million seeds produced per plant, purple loosestrife has the potential to spread rapidly once established in an area.

Saltcedar is the other invader that is causing devastating effects. Saltcedar can quickly become a monoculture along lakes and waterways. A single plant has been reported to transpire over 200 gallons of water per day. In the early morning and evening, moisture with high salt content is exuded from the foliage, causing the soil to become saline. Saltcedar can choke waterways and has even dried up entire lakes (Figure 4). Native riparian species are quickly displaced by saltcedar, which in turn causes displacement of native birds and animals that generally do not feed on the leaves or eat the saltcedar seeds. Saltcedar, even in the seedling stage, will tolerate short-term flooding and can establish away from waterways when seeds are washed in during flooding. Once established the plants can become so thick cattle will not graze the area.

Saltcedar, or tamarisk, is a shrubby bush or tree that can range in size from 5 to 20 feet tall (Figure 1). The bark is reddish brown, especially on younger branches. The leaves are small and flat and resemble evergreen shrubs such as arborvitae (Figure 2). Flowers are pink to white in color, five-petaled, and appear from mid to late summer. The seeds are extremely tiny and similar in size and color to pepper. Each seed has a pappus, which allows it to float long distances in water or move in the wind. Seeds are short-lived and usually germinate within a few months after dispersal.

Both of these plants are still found in flower gardens because gardeners do not seem to see the potential. You can help by removing any you have and ask your neighbor to do the same.

Because of their potential to invade lands that you use, we need your help in identifying any plants found. Even if you are not positive on the ID, please call one of the numbers listed below.

ND Dept. of Ag, Noxious Weed Division:

Toll free Toll-free: 1-800-242-7535


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