herbicides for foxglove
There is good news and bad news. The bad news is that (so far as I know) foxglove is not listed as an on-label use of any herbicide sold here. This means that no herbicide manufacturer has yet carried out structured scientific trials on foxglove. For this reason, there is no "official" herbicide for it, and no manufacturer-backed application method. You must make your own decisions about what to apply and how. I can't recommend any particular product.
The good news is that foxglove responds to most of the usual herbicides in most of the usual ways. For all its poisonous leaves and rapid spread, in the end, it's just another broadleaf weed which can be controlled and eliminated in pretty much the same way you would deal with thistles or Patterson's Curse. The list which follows is not comprehensive, it simply mentions some of the herbicides I have seen used on foxglove, or considered using myself. Nor is it a list of recommendations (though there are a few that I particularly recommend not using). You must make your own decisions.
Selective herbicides are usually best. These target broadleaf plants and (mostly) don't harm grasses or mosses.
- MCPA. ("Agritone" is one of the various trade names for it.) Fast-acting and effective. Seems to be the most commonly used. Needs a penetrant.
- Metsulfuron-methyl. ("Brush-Off", "Associate".) Typically used on woody weeds like Gorse and Blackberries, but works well on foxglove. Comes in a granule form rather than a liquid, which can be a little fiddly but is in some ways easier to handle and measure out. Needs a penetrant.
- Triclopyr & picloram. ("Woody", "Raizon", "Access", many others.) Works well on foxglove. Does not require a penetrant.
- Triclopyr, picloram & aminopyralid. ("Grazon", many others.) I have not tried this but would expect it to be very effective. However, the aminopyralid remains in the dead plant material for a long time (6 months or so). It is harmless to livestock but if (for example) you use hay, mulch, or manure from sprayed areas on your vegetable garden, it can kill your plants. The combination makes a useful and valuable herbicide (for example, it's one of the few things that are really effective against Galenia, a nasty thing which carpets large areas to the west of Melbourne) but I can't see much reason to use it on foxglove when there are milder chemicals which work well. As always, you make your own decision.
- Triclopyr. ("Garlon".) Very commonly used for woody weeds such as broom and Gorse. I have not tried it on foxglove myself. I have heard mixed reports about it, some saying it works well, others not so good. I have thought about doing a few test sprays, but with several other chemicals all known to get good results, there seems no pressing need to trial a different one.
- 2,4-D. Not legal in some countries. Kills pretty much anything. There is no good reason to use this on an easily-killed weed like foxglove.
Non-selective herbicides don't discriminate between trees, shrubs, herbs, and grasses. Just the same, sometimes one of these can be the best answer for a particular task.
- Nonanoic acid. ("Slasher" and various other trade names. Also known as "pelargonic acid".) A non-selective contact herbicide. Very fast and effective on foxglove, but also kills grasses and mosses. Rather expensive. Many brands of it are organic. I don't know what the effect of nonanoic acid is on aquatic life and whether it is safe to use near watercourses or not. I'd guess not, but I don't know. If in doubt, hand-pull.
- Glyphosate. ("Roundup".) Cheap and effective but non-selective - i.e., it kills grasses too. In general, it is better to leave the grasses to grow up and compete with the next generation of foxglove seedlings. However glyphosate is an effective cut and paste herbicide - this last method uses tiny amounts applied directly where they will do most good.
A penetrant helps the chemical spread out evenly over the leaves and soak into where it will do some good. Many herbicides work more effectively in conjunction with a penetrant. Some are self-spreading. The product label always says whether a penetrant is needed. Can you save money by not bothering with it? No. You save a small amount on penetrant, but it costs you more than that in extra chemical to get the same result. More work too.
Dye is really helpful. Yes, it's yet another thing to spend money on, but life is so much easier when you can see where you have been and where you have missed. Red or blue? Please yourself.