Joel Hollingsworth wrote:
Paul, kayomuchi wrote that the St. Augustine grass had spread very quickly over the area the cedar had occupied, and the weeds were holding it back in an area very far from the cedar (opposite side of the house).
Point taken on the allelopathy of cedar (I had forgotten!), and of course about the N, but it sounds like those issues have not been a problem for the conditions and species we're being asked about.
I'm curious what the weeds are exactly, and what else is different between the two sites. My guess was that St. Augustine would normally struggle to get enough moisture in those parts, but the influence of the house, and some extremely deep soil, had helped it out in places. A further guess was that an enormous mass of mycorrhiza had lost its partner when the cedar was felled, and recently found some grass to live with instead, but further reading since my post yesterday suggests that this isn't as likely as I had supposed.
Emerson White wrote:
If you have annual weeds just use corn gluten as a preemergent herbicide next year, stops germination and breaks down to N in the soil which the grass needs in abundance.