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It’s time to divide those plants [UPDATED]
Published 7:59am Monday, May 21, 2012 Updated 10:03am Monday, May 21, 2012Bunkey will sleep well this week. Last fall, he made a note that some of his perennials had died in the middle or just weren’t performing up to their potential.
That means that they will have to be dug up and divided.
Hard sweaty work but well worth it in the long run. It was pretty easy deciding on which plants needed redoing. They were either dead in the middle, too big for their spot or in the wrong place.
Often a sunny area will become shaded as trees mature leading to poor performance of a sunny plant.
Here is a list of plants that need dividing or thinning every one to three years, depending on the soil, the gardener’s preference and either willing neighbors looking to fill their beds or a garden sale coming up.
Achillea, fall aster, penstemon, monarda, dianthus, oenothera, coral bells, delphinium, fern leaf bleeding heart, mums, painted and Shasta daisy, phlox and coreopisis.
Monarda can become invasive, running through the garden just under the soil so she may need to be reined in more often than the others.
In another two years, Bunkey will have to be checking another group of perennials that need thinning or moving (every five years that is). These are: astilibe, campanula, galardia, coneflower, liatris, loostrife, Jacob’s ladder, meadow rue, meadow sweet, heliopsis and Siberian iris.
Some of those, like the Siberian iris will need an ax to divide. The roots are very fibrous and thick. Of course, if any of these plants are attempting to smother their neighbors, they can be attacked earlier, and often, with some perennials.
Attacked is the proper word as they get so dense and deep rooted they take a long bladed shovel and lots of sweat to do the job.
Wait until fall to thin or move iris, Asiatic lilies and peonies.
Peonies really don’t like to be moved and will happily bloom in the same spot for 100 years if they are cut down in the fall and given a bit of fertilizer early in the spring.
While they are quite deep rooted, when transplanted, the roots should be only two to three inches below the soil line. They will grow if planted deeper but not bloom.
Hostas can be divided at any time.
The rule of thumb for dividing plants is if it blooms in the spring, divide in the fall, blooms in the fall, divide in the spring.
There is a good reason for this. A blooming flower is, in effect, pregnant. After it blooms, it wants to set seed.
These activities take a lot of energy from the plant.
It needs from six weeks to two months to recover its strength.
Move it before that time and it will take much longer to recover and bloom well.
A few plants should never be divided. They just don’t like it. They are baby’s breath, (very deep rooted) balloon flower, butterfly weed, clematis, flax, lupine, monkshood and Russian sage so be very careful where you plant these.
You may be working around them for years.
If they end up in a really terrible place in the flower bed, you can, of course murder them and buy a new one.
Bev Johnson is a master gardener for Otter Tail County.
