Nice size pond, El Jefe.
Your marsh marigold would have failed, outdoors wherever you put it. It stood a slightly chance planted in a North facing window indoors with a/c
You would have to be cautious regarding aquatic plantings as some would be difficult to keep under control on that size pond in your climate, Parrots feather would create a stunning effect however you would need to be able to reach and trim it frequently, likely to be bothersome in a short space of time.
Similar with water hyacinth and water lettuce, plants like that on a large pond in your zone would be a liability (hence they are listed as invasive plants in some regions)
Obvious plants that would be reliable and do well:
Deep water marginals with one to two foot deep water over their pot:-
Hardy waterlilies (some are not suitable for zone
, Tropical day bloom and night bloom water lilies, Nymphoides, Water Poppy, in a foot deep of water (need to be able to reach them to thin them out every couple of years)
Shallow marginals, for up to one foot deep water, mostly less than six inches deep, some prefer to be planted in just wet mud:
Anubia, Bacopa, Marsilea, Alocasia* Colocasia, Taro*, Acorus Gramineus Variegata, Cyperus Isocladus, Thalia, Crinum, Ludwigia, Iris (various aquatic species, Versicolor, Ensatata laevigata, louisiana iris Sibirica) Pontederia (Lanceolata is a stunning specimen plant) Saururus*, Graceful Cattail- Typha Laxmanii* (For the cattail look, a fairly easy to control form of cattail) Xanthosoma, Canna (some forms cope well planted in aquatic positions) There are others, a few hundred or so...
* denotes need to be accessible to keep under control
Plant ten of those, vaguely according to accurate advice and you will probably see most of them excel as aquatic plantings for a large pond setting. For some years.
Of course, if you are of a dirt cheap inclination, it may take you till doomsday to acquire such a range of really suitable plants on the cheap. From Walmart's.
Now if you went to a grower or nursery where folk have a bit of a clue, your pond selection would be a different kettle of fish in a short space of time.
The original cost of a few measly plants over time would soon be forgotten and you might notice your pond becomes an attractive long term asset for a decade or two
Regards, andy
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