The Q&A Archives: Winterizing Perennial

Question: I recently purchased a large amount of perennials consisting of,Hydrangea Petiolaris Climbing Hydrangea, Monarda 'Jacob Cline', Salvia x superba 'May Night', Astilbe chinensis 'Vision in Red', Phlox paniculata 'Blue Boy', Miscanthus sinensis 'Little Zebra' and
Hemerocalle 'Double River Wye'.My question is, How or what do I do to prepare these plants for the winter? Do I prune before the frost, and if so, how far back? or do I prune in the spring, and again, how far back? I have asked these questions from the greenhouse staff, and what they are saying is that I prune in the late fall, about half way back but close to a mid-point stub. I am sorry that these questions are confusing, but unfortunately, upon purchase, there are no answers to these questions on the tags. I did buy some perennials last season, and none of them came back this year, so I was leary on buying these purchases, but I am willing to try once again. Please, is there anything you can help me with?

Answer: I think the easiest approach is to take your cues from nature. I would not recommend pruning anything down in the fall. Pruning encourages new growth which would not have time to harden off and therefore would be susceptible to frost damage. If plants are allowed to harden themselves off (which they do gradually as the weather begins to cool) they will suffer less winter damage. So, allow everything to grow, slow, and then sleep during the winter months. In the spring, after new growth begins, you can safely prune things back.

Hydrangeas can wait until spring to be pruned and aside from a protective mulch over the root systems, won't need any special treatment. When you prune, cut the canes back to about 18" above soil level. Ditto for the Monarda. Salvia is not always winter hardy, but after the tops die down, mulch over the soil to protect the roots from winter cold. Astilbe will die back in mid- to late summer all on its own. You can pull or rake away the dead foliage. Mulch over the soil at the end of summer to help protect the roots over winter. Miscanthus tops will die down with first frost. I leave mine alone because I think the dead foliage is attractive in winter. The foliage can be pruned away in early spring. Hemerocallus tops will die down on their own in late fall; treat as you would for Astilbe.

Hope you have better luck with your plants this time!

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