Home Depot (HD) and Lowe’s (LOW) have the most at stake among retailers facing a dockworkers’ strike, with possible port closings cutting off shipments right before the lucrative gardening season.

Home Depot, the biggest U.S. home-improvement chain, is making plans in case 15,000 workers at ports from Maine to Texas walk off the job, and Lowe’s said that it is monitoring the talks. About 45% of the commerce that flows in an out of the U.S. goes through East Coast ports, according to the National Retail Federation.