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Name: Carrie
Location: N/A
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Question:
I'm steward of a section of a railroad right-of-way where many native prairie plants have flourished for years. I've taken care to remove woody plants, europeon thistel, ragweed, etc. Suddenly, I've been overwhelmed with a Europeon plant called "teasel." I've tried removing the entire plant manually but it is very labor intensive. I've tried cutting the seed cones before they've had the change to drop more seed.

What is the best way and what is the easiest way to eradicate this overpowering species which is choking out and overpowering my beautiful indian and big blue stem grasses. I'm too the point where I'll even use herbicide, if necessary. What do you recommend?



Replies:
Dear Carrie,

The following web page on its control is apparently under construction
http://www.css.orst.edu/weeds/Teasel/control.html
however the email address noted is Sara.Griffith@orst.edu

Anthony R. Brach


In reference to teasel:

It is very difficult to get rid of the stuff:

The average plant produces 3000+ seeds Seed viability is 6+ years plants remain photosynthetically active when native species are dormant Plants smother competitors with their rosettes, thus providing an optimum nursery for new teasel plants (the plant dies after it flowers) Seeds of cut, green flower heads show 90%+ viability after 7 months Teasel seed floats and can be dispersed by water. Thick tap root can penetrate over 75 cm (27 inches) deep

It is imperative that ALL teasel flower heads be cut off at this time of he year, bagged and removed from the site you are trying to restore/preserve, and preferably destroyed by fire or placed in plastic bags out in the hot sun or in a hot compost pile in order to kill the seed. (you can use composted or sterilized material for home garden compost, but I do not recommend taking it back to the natural area in case there are survivors).

Remaining floweringstalks should be cut at or just below soil line with a sharpened shovel or hoe to prevent rebloom. If the stalk does not contain flower heads, it can be left on site. Cut flowering teasel removed in this fashion should not rebloom and will die at the end of the growing season. Rosettes should be herbicided (the deep root precludes digging all but the smallest plants).

Herbicides we have tried at our many teasel infested sites include Garlon and Roundup. We have had inconsistent results with both. In general, the herbicides are most effective applied in early spring (April/May) when the teasel plants contain much succulent, soft growth. Kill in these cases has exceeded 95 percent in some instances. Later in the season or at some other sites, such as in summer, there is only partial control or kill, with kill rates sometimes less than 75 percent. I feel this might be due to a tough coating and many hairs on the leaves which repel water, or drought stress on the plants (the herbicide does not translocate as well, and the label states that control effectiveness is decreased with drought stressed plants). Also, larger cut leaf teasel plants which have begun to bolt (form a flowering stalk) hold cups of water in the leaves next to the stem, and this may also serve to dilute or weaken the herbicides applied. It is possible that surfactants may help overcome the problems with leaf coatings and hairs. (IF ANYONE HAS HAD CONSISTENT SUCCESSFUL (> 95% kill every time) RESULTS - WITH HERBICIDES, let me know).

Concentrations of herbicide we have used:
Garlon 4 + surfactant in water 3% solution Roundup Pro in water 5% solution (2% active ingredient); if using consumer Roundup concentrate will need to use 12% solution + spreader sticker (surfactant)

Avantages to Garlon - will not kill grasses when applied at above rate Disadvantages - can volatilize and affect nearby vegetation at high temperatures - do not recommend applying at temperatures over 75 degrees F (24 C) On one site we have treated a teasel monoculture 4 times during the spring/early summer over the last 3 years, the first 3 times with Roundup, then the last treatment with the Garlon 4. The first 3 treatments killed all of the growing plants, which were immediately replaced from the seed bank. Finally, this year, after the spraying, only a few seedlings have appeared. This is what it takes to deplete the seed bank in an area with a strongly established population.

In a natural area, you might also try a stronger solution of Roundup, perhaps 23-33% solution, and wipe it directly onto the foliage with a wick applicator such as a sponge brush, or preferably a commercially available "swiper" applicator.

The key in all cases is NEVER, EVER allow a plant to drop its seed on site or to leave the cut flowerheads on the site.

Joshua Skolnick
Restoration Ecologist



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