🚀 go-pugleaf

Some anecdotal observations of a footloose naturalist:

Lythra is often seen in dredge spoil piled on  Spartina marsh, i.e. in a
somewhat saline environment.  It likewise occurs in undisturbed brackish
marshes slightly upgradient, saltwise, from stands of Typha
angustifolia.

In contrast, white cedar in this area (suburbs S of Boston) is absent
from salt marsh edges, preferring a low pH oligotrophic environment such
as found in peaty depressions with little flow-through.

I'd say that insofar as you can restrict water movememt and buffering
action in your wetland, cedar will be favored.  If, on the other hand,
some salt along w/nutrients and neutralizing agents are present, Lythra
may take hold.  It is rare to see them occurring together.

Thomas Palmer
Milton, MA