I have participated in prescribed burns where the fire was only a few inches tall barely creeping through the leaf litter. I returned the following summer and found seedling buckthorns were not killed. A number of people have said frequent fire will keep buckthorn or bush honeysuckle from getting established. I wanted to see this for myself.

I found a buckthorn seedling growing in my sedge meadow garden. The buckthorn seedling was probably a year or two old. Instead of removing it, I marked the location of this buckthorn seedling so I could put a flag by it after I burned the sedge meadow. The sedges were about knee high, and the fire was hot enough to singe adjacent arborvitaes above waist high (oops).

Above is the flag I put into the burned sedge meadow to mark the buckthorn seedling.

This is a closeup view of the buckthorn seedling after the sedge meadow was burned.

This is an image of the burned buckthorn seedling a year later (a few days ago). I cut away the sedges so I could get a photo of the burned buckthorn seedling. The bark has peeled off the seedling. Since it has not sprouted after a full year, I am declaring it dead.

If fire is hot enough, it can kill small buckthorn seedlings.