Q.Winter Care Of Medusa Allium In A Planter Box
I am in the 5b-6a plant hardiness zone. Our plants are outdoors (in a big planter box that has at least 12” of soil) in a sunny location without a shelter overhead. Should I deadhead them all now, and after a week or so, cut them down to just above the soil and put 3 or more inches of mulch on them. Do you think they would survive the winter? Thank you!

Certified GKH Gardening Expert
They are hardy to zone 4 so you should be OK if they are mulched well. Cut them to the ground when the stems have yellowed and withered, which allows them to gather energy for next year's blooms. Then cover them with at least 3 inches of mulch. Be sure to pull the mulch back in spring. If you are very worried about them, you can dig them up and store them in the garage over winter.
https://www.gardeningknowhow.com/ornamental/bulbs/allium/allium-post-bloom-care.htm
https://ask.extension.org/questions/438718
https://www.gardeningknowhow.com/ornamental/bulbs/bgen/bulbs-dont-need-chilling.htm