Growing Concerns 523: Dividing poppies, Viburnum bushes

Early Summer!

Take a firm stand to divide and control pushy poppies


Dear Janet,

Poppies are taking over my yard and pushing out all my beautiful irises. Please tell me how and when to divide the poppies. I have read that they do not like to be disturbed.


Dear K.T.,

If ever there is a good time to disturb a plant, you've described it. Your poppies have crossed the line to become weeds, a category most effectively defined as any plant growing where it's not wanted. A wise gardener has no sympathy for weeds.

Most gardening authorities suggest late summer or early fall to divide perennial poppies such as oriental poppy (Papaver orientale). This is when the new foliage emerges after the plant's summer dormancy, announcing its exact location.

However, the same experts will tell you that regardless when you dig them, established oriental poppies are difficult to eliminate. Their roots are deep, easily  broken and every substantial piece left behind in any season is likely to sprout a new plant. So it's not for the sake of the plant's simple survival that we divide poppies between July and mid-September. We could dig them any time -- I have successfully moved them in every month of the growing season, as needs dictated. The late summer recommendation exists because those moved then are most likely to be established well enough to bloom the next June.

Dig deep to divide a poppy. Coax or rinse the soil from the root mass so you can see what you're doing. Then cut to isolate a piece of the fleshy tap root that has an eye or leafy sprout. Respect the plant's original orientation when you replant -- keep the eye up and the root descending straight down.

That said, poppies don't need division. Unlike daisies, irises, mums and other short-lived perennials that put on their best show if rejuvenated every few years by division, poppies can be left in place for many years and still bloom well if all growing conditions remain favorable. We divide them only to spread or share them. So those poppies that are in the right places in your garden can be left alone.

The weed poppies are your real challenge and you should try to kill them, not save them. It's okay. The original plants won't hold it against you.

Dig out your irises -- it's a good time now to divide them. Then dig through the bed and remove every bit of poppy root you can find. Divide the irises, reducing them to bare root to eliminate poppy roots entwined in the iris. After replanting the irises, check the bed regularly for poppy shoots and nip them off as soon as you see them.

Or move the irises to another location near less aggressive plants. Pair the poppies with something slow to start in spring and ultimately taller than poppies, so it can tolerate some weeds at its feet. Butterfly bush (Buddleia davidii) and New England aster are two possibilities.


Dear Janet,

Three years ago we had new landscaping done in our backyard. Under a large shagbark hickory we had three verbena bushes planted. I don't recall if they bloomed the first year but I do know they have not bloomed the past two years. They are quite healthy but with no blooms in spring, quite boring.

We trimmed them last fall because they were growing so large. Did we do the wrong thing by trimming at the wrong time?


Dear J.S.,

Most spring blooming shrubs set flower buds for the next year during the second half of summer. So pruning after mid-July will remove at least some of the flower. Drastic or repeated pruning can remove every blossom or so many that the few survivors may have passed your noticed the next spring.

I don't think there are any shrubby verbenas that grow in your area. Perhaps your shrubs are viburnums, large bushes often placed in the shade. There are many kinds of viburnum, however. The species and variety may offer more clues -- doublefile viburnum and certain European cranberry viburnums, for instance, may fail to bloom for reasons other than pruning. Call the landscape company that planted for you and ask for the entire name, or send me a small branch with leaves.

Short report

Mildew season approaches.

You're likely to see it disfigure foliage again if you didn't thin the stems of a mildew-prone tall phlox or bee balm in spring or apply a preventive fungicide several times at seven to ten day intervals in June. If you can't do this for such plants, perhaps you should replace them with mildew resistant varieties or entirely different species.


Green thumbs up

to gardeners who share information, such as you who continue to write to add such plants as Kerria japonica, pokeweed and sycamore trees to the list of this winter's losses. It's a comfort to know we aren't to blame for every dead plant.


Green thumbs down

to the inability to let go. Some plants are simply not right for you or your garden. If it spreads too quickly, falls too easily, fails to delight or carries too much baggage in terms of pests, send it to the compost. Try something new!

Originally published 7/5/03