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The Garden Plot for October 12, 2007
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: “Dividing Perennials”
Every summer we inevitably get questions about transplanting or dividing plants that have grown too big or just seem to be in the wrong place. We always advise to wait until the hot, dry days of summer are over before disturbing plant roots. Once the days are cooler and we start to get fall moisture, chances of plant survival are much better.
Now is a good time to move or divide perennials that bloom from early spring to early summer (June). Newly moved perennials will need approximately six weeks to settle in before the ground freezes hard. That is usually about the end of November or early December in most of Western Montana. If your garden is at higher elevation, the ground may freeze hard several weeks earlier.
Perennials that flower from midsummer onwards are best moved and divided in the early spring. If you have to divide late bloomers in the fall, prune them back by one half, if they are over two feet in height. This will help balance the top growth with the now-diminished root system. You will most likely sacrifice some bloom next year on species such as Rudbeckia or Summer Plox, but that’s the price to pay for survival.
The following is a list of the best times to move or divide particular species:
Bearded Iris are best divided in July or early August. For more information on iris, you can try the American Iris Society website. There are local iris societies in Western Montana as well.
Peony should be only be moved or divided in the fall; they are a bit picky. Don’t be too stingy when dividing peony. Try to include a large amount of woody root with at least 3 to 5 growing points.
Asiatic, Oriental, and Trumpet lilies move with ease in the fall. Dig up the clumps, separate the bulbs, and replant them. There is rarely ever a shortage of bulbs in a large clump of lilies. You may want to share with friends and neighbors.
Daylilies and Hostas are less picky and can be moved or divided in the fall or the spring. If the foliage is especially exuberant this fall, prune it back by one third to one half.
There are some species that just don’t want to be moved in the fall. These include ornamental grasses taller than three feet and Butterfly bush.
For all newly divided or transplanted plant material, make sure to water them in so that you get good soil-root contact and the roots get a chance to settle in.
Nest week we’ll talk about whether or not to add amendments when planting or transplanting trees.
Helen Atthowe's new short program of gardening tips
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