Q I planted several butterfly bushes about four years ago, and they have been doing great. I know they are not really hardy in our zone, but I cover them with 3 feet of mulch every winter and they survive. I'd like to transplant them away from our house. Will they survive?
A Butterfly bush (Buddleia davidii) grows to be a large, multi-stemmed shrub in areas where it is hardy (Zone 6 and warmer). In Zone 5, it dies back to snowline or to the ground but usually regrows, like an herbaceous perennial. In Zone 4 (which covers most of the southern half of Minnesota), butterfly bush will survive only if we have a mild winter or if extensive winter protection is provided. It sounds like your thick layer of winter mulch combined with your slightly warmer location (near Lake Pepin) has allowed you to grow this plant successfully.
With its irregular form and lanky, arching stems, butterfly bush is not the tidiest of shrubs. But its big draw is the profusion of narrow, cone-shaped flower clusters it produces from midsummer to autumn. The purple, lavender, pink or white flowers are a magnet for all sorts of butterflies. Even in areas where it's not hardy, it's worth growing butterfly bush as an annual just to watch the butterflies it attracts.
Butterfly bush usually transplants easily. As with many herbaceous perennials, early spring is a good time to transplant butterfly bush. Late April to early May is the best time, but since butterfly bush is often late to break dormancy here you can probably push that to mid-May without much trouble. Carefully dig up the plants, preserving as much of the root system as you can. Replant right away in the new location and be careful to avoid letting the roots dry out. Be sure to keep the plants well watered as they get reestablished in their new location.
Q What should you do when you receive plants too early from mail-order catalogs? I received some Asiatic lily bulbs in April, and they were already starting to grow. Should I wait until after all danger of frost is passed to plant them outside or should I plant them now?
A Getting mail-order plants early can be a problem for gardeners here on the northern fringe. Most mail-order nurseries do try to time shipments based on the growing season the plants are being shipped to, but the timing isn't always right.
While Asiatic lilies are quite hardy, the new growth from the bare bulbs would probably be too tender to be planted outdoors now. (The same is true of bare-root or container trees, shrubs and other perennials that are starting to leaf out when you receive them too early.)
Call the nursery company that you ordered from and explain the situation. See if it will credit your account and resend the bulbs or plants at the appropriate time.
If it can't or won't do this, you'll need to pot up the plants and tend them until they can go outside. Use a good-quality potting mix and thoroughly water the plants after potting. It's not ideal to keep these potted plants indoors, since your house will likely be too hot and dry. A better choice is to keep them in a cool area that will stay above freezing until you can move the plants outside. A garage may do the trick. Keeping them cool also helps acclimate the plants so you can move them outdoors sooner, without waiting for our average last frost, which is in mid-May.
Nancy Rose is a horticulturist, writer and photographer. To ask her a gardening question, call 612-673-9073 and leave a message. She will answer questions in this column only.