Green Side Up

Garden talk with Gazette community blogger Janice Peterson.

Make sure perennials are really perennial where you live

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Janice Peterson
Monday, September 16, 2013

Friend-of-the-blog and Janesville Gazette reporter Cathy Idzerda recently wrote an article about the benefits of planting perennials in the fall. She's right, it is a great time to plant perennials for many reasons – plants can develop deep root systems and aren't as stressed by heat, insects or the need to produce flowers. It's also a great time of year for the gardener – you aren't busy planting annuals and you've spent the whole summer looking at your garden with a critical eye. Perhaps you've visited other gardens and gained some new ideas. It's a great time to reassess your garden and think about where new plantings might be in order.

There are some cautions when buying perennials, however. I've found at some big box stores plants can be labeled “perennial” when in fact they are not perennial here in southern Wisconsin. My guess is that the stores provide plants to all their nationwide locations and so these plants may indeed be perennial somewhere else. I recall seeing purple fountain grass labeled as a perennial in a Janesville chain store. There is no way this plant will survive a typical Wisconsin winter. However, purple fountain grass is really great to plant as an annual in fall containers. But believe me; if you plant it in the ground now it will be dead by spring.

Another fall plant that can be confusing is the garden mum that we see for sale everywhere this time of year. These showy mums have been pushed to the limit into putting most of their energy into producing huge numbers of flowers. Root growth is not their first priority. Yes, with proper care (this involves watering, mulching, deadheading and I think perhaps rattling chicken bones over them) they can survive the winter, but don't count on it. I know one gardener who told me she over wintered potted mums in an unheated garage and was able to plant them successfully in the spring, although I haven't tried this yet. Mums are super beautiful, a wonderful symbol of fall and inexpensive, so I suggest treating them as annuals and if they do come back in the spring consider it a bonus. On the other hand, I've had great luck overwintering New England asters, perhaps because they finish flowering sooner than the mums and can spend some time developing roots.

How do you avoid buying a plant that is not hardy where you live? Here are four surefire tips:

1. Read labels. (Is the hardiness zone for the plant listed? Rock County is zone 4a/5b.)

2. Research the plant's growth requirements from reliable books or internet sites.

3. Buy from sellers who have well-informed staff, such as local garden centers or plant sales at botanical gardens. They make sure to offer perennials that are appropriate for their area.

4. Divide and share plants with neighbors and friends. (Just make sure it isn't being shared because its growth is too aggressive!) This is one of my favorite ways of getting new perennial plants. You'll be sure to get a plant that's been tested in your area, and the price is right!

Janice Peterson has worked as a grounds horticulturist at Rotary Botanical Gardens in Janesville since 2002. She is a master gardener with the Rock Prairie Master Gardener Association. Though her education is in plant science, she considers her love of gardening and strong back to be her true qualifications. Janice is a community blogger and is not a part of The Gazette staff. Her opinion is not necessarily that of The Gazette staff or management.

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