Plants or tubers? It's too early to put plants outdoors yet, needs to be past last frost date (last week of May) but you can plant tubers this month indoors or in a greenhouse and grow them on.

Non stop tubers
they need 3 weeks so may is ok I guess

Well May is fine - they can't go outdoors till last week of May anyway.

Got 9 popping out out of 10. The other one looks OK Just nothing . Fun finding out.