The message
from Amy Fong contains these words:

I have a rhubarb problem. I had dug them out (or at least I thought I did)
and planted cedars in the same location. The rhubarbs came back and are
now like 2 feet tall.

What's a good and effective way of getting rid of the rhubarbs without
risking the cedars?

Just keep pulling off the leaves and stalks whenever they appear; they
will snap off at ground level. The roots won't survive long without
leaves providing photosynthesis, and you can just leave them in the
ground to decompose harmlessly into humus.

Janet