Jessica Damiano's award-winning garden blog gets to the root of things.
Saving the garden from saltwater damage
Much of Long Island, especially the South Shore and East End, was inundated with salt water when high tides encroached upon landscapes during superstorm Sandy. Left alone, the salt will form a hard crust and end up completely dehydrating the soil, so you must move to flush it out.
Depending on the exposure, it may be too late to save your plants, but for the health of the soil and your future plants, you must repeatedly water to leach out the salt. Take care that your irrigation water doesn't run off into the street; keep it in the beds only.
If saltwater exposure was extensive, as it was in so many places, my friends at the Cornell Cooperative Extension of Nassau County recommend that you water and then spread gypsum over the soil. The salt will have a chemical reaction with the gypsum, forming sodium sulfate, which will wash through the soil with more watering, leaving harmless calcium precipitate in its place.
As far as plants, trees and shrubs go, if you didn't water them thoroughly and completely immediately after their exposure to salt, they're likely too far gone by now.
More advice from the CCE:
Replanting unearthed trees
Reset only small, easy-to-manage trees. Keep roots covered and moist until resetting. Replant trees and shrubs at their original planting depth, packing soil firmly around the roots to eliminate air pockets and provide support. Stake the tree for about a year or less, until its roots become re-established, using three stakes, each placed at an angle away from the trunk. To avoid injuring the trunk, fasten a tree to its supporting stakes with a wide strap. And be sure to water the reset tree.
Prune branches that are broken or dead with proper pruning cuts, but prune trees only when bark surfaces are dry. During the dormant season, an arborist can prune your trees to increase wind resistance, however the tree still must have been planted properly and not be in compacted soil.
Replace lost soil that may have washed off of tree roots. To increase tree vigor, apply compost, which will improve drainage, soil texture and soil nutrients. Remove sediment deposited over the roots by the flood. Roots usually extend at least as far out as the canopy, which is the reach of the branches.
Remove all debris, silt and mud deposited on the lawn from the storm.
Never top off trees
Reducing the length of branches will not help avoid breakage in future storms. Topping is one of the worst things you can do for your trees; new branches that are attached weakly tend to grow and therefore are even more likely to break when a storm strikes.
After repeated watering, a soil analysis is recommended: Contact Agro-One (730 Warren Rd., Ithaca, NY 14850; call 1-800-496-3344; dairyone.com/AgroOne) for sample-gathering and mailing instructions. Fees range from $12 to $15 per sample. You can also pick up a mailer at the Nassau CCE office at 832 Merrick Avenue, East Meadow (hours are: Tuesday, 10 a.m.- 4 p.m.; Wednesday and Thursday, 10 a.m. - 1 p.m.; website: blogs.cce.cornell.edu/nassau).