Answer: To some extent your lack of success may have had as much to do with the plant choice and soil conditions other than salt. The hardier lavenders such as Munstead and Hidcote are not reliably hardy in zone 5, but for best success they absolutely need a well drained location. So it is not too surprising that the lavender did not make it. Thyme will also fail to survive cold winters unless the drainage is excellent. So if you have a heavy soil or water collects where they were planted, that could explain at least part of the problem. Also, both of these have foliage and stems overwintering above ground, this increases their exposure to the salt. So using an evergreen or semi evergreen is not usually the best choice. There are several things you can try to do. One is to set them a bit back from the road and erect a barrier such as a burlap screen. Plant on a slight berm so that the drainage is improved, and then in the spring, as soon as salt season is over and the ground has thawed, try to leach excess salt out of the soil using water from the garden hose. Also select hardier plants with some tolerance to salt such as sedums or dianthus or barren strawberry. Here is a link to a list of hardy plants with some salt tolerance that you may find helpful. You may need to cut and paste the complete url to make it work correctly in your browser.
I hope this helps.
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