I am battling the invasive species, Creeping Bellflower. Not realizing what the pretty purple flowering plant was for too long, it invaded much of my landscaping and needs to be eradicated. Bellflower is under many mature bushes such as Montgomery pines, CO Blue Spruce, Lilac, Cottoneaster, etc. Due to the mature size of the bushes, I am not able to get under them to dig it out as they are close to the ground, and it's too prolific for digging to be effective.
I have researched to find that presently the belief is that Triclopyr is the most effective herbicide, available to homeowners, to kill Creeping Bellflower. Repeated applications will be necessary.
My concern is that although I do not plan to spray Triclopyr, but rather "paint" it on each leaf (ugh, what an arduous project!) I am concerned the herbicide may reach the roots of the bushes/plants below and kill them off as well, after eventual rain, watering of surrounding plants, or dripping from the leaves to the soil after application. I very much will appreciate your expertise and advise on killing the Creeping Bellflower but not the roots of the bushes growing beneath it.
I sprayed Garlon 4 (triclopyr product) on undesirable brush and it wilted young oak tree leafs nearby. I thought the vapors may have caused the wilting. The oaks all recovered. I have treated invasives like oriental bittersweet with good success with triclopyr... it is recommended.
Garlon 4 does have some soil activity. So it can move from your target to your desirable trees.
i would say the soil activity of trichlopyr is negligible and don't worry about it. Root grafting transferring the chemical from one plant to another is real and could be a concern. If the translocation is a big worry, use glyphosate. No residual soil activity and translocation not as much an issue. It may not be as effective so more repeat applications would be necessary. A small spray bottle will give you precision with minimal overspray and make for an easier application. Concentrate application may not be as effective as diluted applications due to the quick death of cells preventing the translocation of the chemical. Coarse droplets will have less overspray than fine ones. Small amounts of overspray are usually not an issue. Don't soak the leaf to minimize runoff. Most chemicals penetrate fairly quickly so a 48 hour rainless period after application should give it plenty of time to get to work with minimal residual runoff. A bigger concern if using an ester version of trichlopyr (oil based) is temperature volatility. Above 80 degrees it will release vapors that can damage nearby vegetation. An amine (water) based formula will not volatilize but usually needs a surfactant such as a crop oil or a soap solution to effectively penetrate the leaf cuticle. Timing is critical with growing season applications most effective. Some plants are best treated late summer as nutrients translocate to roots carrying the chemical with it, other are best treated in spring before a thick cuticle has a chance to develop. Your local county ag rep should have good info on how to treat your problem. As always, read and obey the label.
Garlon 4 = ester formulation
Garlon 3A = amine formulation