Division is the answer for seasoned perennials
Is it mid-May already? A cool breeze rustles tender new leaves on the oak trees – they must be 100 shades of green right now. This is the most vibrant reminder that the season has, indeed, begun. Quite often as we exuberantly bound outside with trowel and shovel shouting “to the garden!,” we overlook certain chores in favor of getting the beds ready and buying new plants. Our lives have become so full and complicated that certain tasks are disregarded or avoided all together. Next year, you say, or in the fall. I’ll do it in the fall.
Sometimes I think of the garden as not so much an object of formal design using living plants within an intentional plan. It is more like the plants are an assemblage of characters in a play, as the plants themselves take on qualities and temperaments that may or may not have been exactly what one had in mind when they were first planted. But now, right before the performance begins, all of the backstage is whispering in anticipation: “I hope they do something about these dreadful costumes.”
There are many reasons why dividing plants in the spring is a rather good idea. Most of the woody plants – including lavenders and sages – generally will not ever require division.
Yet, even the most unfaltering perennial will respond to division over the years, but only if they look over-grown or seem disheveled or distracted by, say, an invasion of other plants. Plants are like children, if given love and care they’ll behave and act the way they are supposed to. Ignore them, and you get mayhem.
The great divide
I used to be a stickler for following the rules: prune spring flowering trees in the fall, prune late summer shrubs in the spring and divide some plants in the spring and some in the fall. Now I divide and prune and relocate whenever the plants seem to need it, and perennials can get pretty unruly if you don’t inspect them. Some will dare to go bare in the middle or exhibit overflow aggression by spilling out into another plant. A good rule of thumb is you can divide or move a plant when it is not flowering. This way all the plant’s energy can go to root and leaf growth for recovery. I think it also has more to do with the confidence of the gardener than anything else. I’ll move any plant now – in bloom or not – as over time I have developed an understanding and compassion for plants and birds and everything else that is connected to living life with joy.
Perennials will respond to division by bursting forth when they have more room to spread and with a little forethought, plants can be moved and divided any time that is convenient for you, as long as you do it soon – while the cool weather is with us.
A common mistake that many of us make is to plant things too closely together for the “instant gratification” factor. Mallow will grow into in immense, immutable mess if it is not kept under control by severe cut-backs for re-bloom during its flowering stage and by dividing before it gets too big.
Bearded Irises will become armies with their rhizome “feet” marching to invade wherever they are set and then stubbornly refuse to bloom if you do not divide them every other year. I enjoy finding amusing places to park these – circling around a big rock, lined up along a path – the sentinels of dignified grace, irises are marvelous even when not in bloom.
Save the parent plant and you will get strong and healthy new plants by slicing into the healthiest and most vigorous outside edges. Discard old, woody roots from the middle section (add them to the compost pile).
Many plants freely give off seedlings, such as lady’s mantle, Oenothra, moonbeam coreopsis, silver king Artemisia and turtlehead. These can be rounded up and planted as a group to form a new clump.
Certain perennials, such as bee-balm, bellflower, cranesbill and sedums, will fall apart when dug from the ground. Others, like Astillbe, ferns and Siberian iris, will require a hand saw or a pitchfork.
Unless you are opening a flower stand, pick the healthiest-looking pieces and discard the rest in the compost heap. I am sure I am not the only one who finds throwing these bits away hard to do. We tend to get attached to our perennials.
Always water everything well before, during and after the dividing of perennial plants, and always prepare the area with fresh, composted soil in the spot where you plan to put your new divisions. I know, this seems perfectly logical, but sometimes it is necessary to “hold” the new divisions for a day or two, so keep them moist and wrapped in newspaper while the comfy new bed is being prepared.
Last but not least, when there is a surplus, give plants away. Throw a perennial swap party, leave plants with neighbors, and don’t forget to stop by and ask if your town hall, library, senior home or school might have a welcome spot for cherished plants from the garden.