I'm also in Zone 5, so I would wait until after our last frost date which is May 10th. This could depend on the weather, of course.

'Last frost date' is really only a guideline for when to plant out frost sensitive plants, like annuals and most veggies. Honeysuckles are not frost sensitive and if the plant has been acclimated to outdoor conditions (sold outside and not plucked from inside a greenhouse), you can plant whenever you like. My concern would how well it might survive a zone 5 winter in a planter box exposed to winter cold. That is a far more harsh environment than if it had been planted in the ground and you run the risk of the root mass freezing solid. Typically you need to select from plants that are winter hardy to at least 2 zones lower than yours but even that is no guarantee.

Thanks GG for the info. I would still recommend to hold off on planting anything as our weather is still iffy. Here in our neck of the woods, they are forecasting snow on Tuesday, but 50's for the next couple of days. Better to be safe than sorry.