Canada goldenrod control
As I wrote, most of our Canada goldenrod patches are primarily along the edges of the prairies, and hence are relatively small. The leaf spritz technique we use is ideal under these conditions, since it permits very selective treatment of the goldenrod without affecting adjacent plants that are even fairly close.
We use a 20% mixture of triclopyr (Garlon 4) in bark oil, dispensed with a hand-held spray bottle. A few leaves on the upper part of each stem in the clone are given a brief "spritz". The few leaves spritzed are high enough on the stem so that no stooping is needed.
The photos here show what a plant that was in full flower bud looks like after about 2 weeks. The adjacent untreated plants are completely unaffected.
I admit that this is a relatively slow technique, since one has to deal with each stem individually. However, this has the advantage that nearby good plants are unaffected. Marci and I were able to treat about a dozen reasonably large clones (15-30 stems each) in less than an hour.
As in most invasive plant control, the best time to initiate attack is when the problem is still small. Now is a very good time to do this, since Canada goldenrod is in flower and hence easy to find.
If all the stems in a clone are treated, you get rid of the clone for good. Last year when I first used this technique, I marked some treated clones and found no new growth this year.