Q. I had an African sumac tree removed. I believe that the removal crew treated the stump with something to prevent the tree from regrowing. Now the xylosmas I planted in that spot have yellow or brown leaves. Is flushing the soil with water the best treatment?
A. A common treatment to use on the stumps to prevent regrowth is applying potassium nitrate, a.k.a. saltpeter, one of the so-called “stump removers”. There is nothing poisonous to plants about the potassium or the nitrate. It’s the concentration of this chemical that does the job. It’s a salt.
|This is a stump remover marketed in Australia. It clearly shows that it's made from potassium nitrate. Notice the fertilizer analysis on the right of the label. In light applications, it's a fertilizer. When it's applied in large amounts, it's a plant killer because it is a fertilizer salt. http://i.ebayimg.com/00/s/MTYwMFgxNjAw/z/7OAAAOSw-ndTnilN/$_35.JPG|
Any salt applied in high concentrations will kill plants. It is not a good idea to apply table salt because this salt contains sodium and chloride, both poisonous to plants. But potassium nitrate is also a fertilizer. The dose makes the poison. This fertilizer is applied at a concentrated rate that kills.
As with all salts, they flush easily from soil if you run lots of water through it.
There are other chemicals besides salt used to control regrowth from stumps. These are specific weed killers or herbicides that are very good at killing woody plants. Hopefully, these chemicals were not used.
|This is a stump remover that uses a chemical herbicide instead of potassium nitrate. http://images.lowes.com/product/converted/071121/071121564207.jpg|
The pictures you sent to me looks like some form of chemical damage. Hopefully, they used potassium nitrate and you can simply flush the soil with water several times. If herbicides were used, the soil might need to be replaced in that area.