Ask Mr. Smarty Plants

I compared the list of salt tolerant plants to the list of shade plants prepared by the New York City Department of Parks and Recreation.  I also checked for plants that will grow in part shade, are salt tolerant and drought resistant.

The only plants that were fully shade tolerant and salt tolerant  and might make it with your water conditions were the following shrubs.  I think that they will be too large for your needs but am including them just in case.  If you have a ditch along the road,  I would plant them on the sides of the ditch to get their roots closer to the water table.  Or you could build little hollows, like small rain gardens and plant them at the bottom. Spicebush seemed to need the least water.  If you are planting in the zone of lots of tree roots, the trees will be competing for water, making this area drier for the plants.

Photinia pyrifolia (Syn = Aronia arbutifolia)– Red chokeberry  is a six to twelve foot shrub with four-season interest.

Lindera benzoin– Spicebush grows six to 12 feet and needs medium water.  It will also grow in dry soils.

However if you can prune up the trees, or thin them, so the site gets 3-6 hours of sun a day, you could plant Schizachyrium scoparium– Little bluestem.  A large planting of this will give dramatic fall color and also be beneficial to wildlife. AND it's drought resistant. So this sounds like the ideal plant for you.

The rest of the salt-tolerant plants are all sun loving and need six or more hours of sun a day.  This is because they developed along open, sunny beaches or in salt marshes.

Schizachyrium scoparium