Well, I finally dug out all of the perimeter drains along the side of the house, about 27 feet of them in all. They are the old concrete two foot lengths of pipe laid side by side around the house. One corner had been stove in by the installation of a fence post on top of it. Thus, this corner [not the corner where the seepage entered the crawl space, by the way] was completely plugged with earth and roots. The others did not have any roots inside them as it turned out.
I am still planning to clean the front and back drains [all concrete] using the Jetter. First I want to get the new plastic drain tiles in place, however.
Thank you for your advice and input. Much appreciated.