March garden happenings

It’s time to think about cutting back in the garden.  Last fall I took horticulturist David Salman’s advice and didn’t cut back my perennials. As well as providing shelter to beneficial insects, he says, “perennials are more cold hardy when their stems are left standing over the winter.”

Some of our perennials are showing signs of green around the base.  I will remove all the dried stems above the new green. Thanks to recent storms our garden soil is moist so we’ll probably start watering next week.  As we walked the neighborhood last weekend we noticed quite a few people out in their yards watering and tidying up.

Living on the edge of town, a lot of unwanted grass seed blows into our yard and now is a good time to dig it out.  I don’t use weed killer on it as the grass is so entwined with desirable annuals and perennials that I’m sure I would damage the ones I want.

Spring is a good time to divide fall blooming perennials. Over the years clumps of perennials can become root bound and don’t thrive.  Digging them up and dividing the clumps can reenergize the plants.  It is easier to see what you are doing when the leaves are small.  Also, smaller leaves and shoots will not suffer as much damage as full-grown leaves and stems according to the University of Minnesota Extension (UME) website. It’s a good idea to soak the area around plants you plan to divide a day ahead of time.  It will make digging a lot easier.  Remember, it is never a good idea to divide plants when they are blooming as a lot of energy goes into producing flowers and not as much will be available to encourage new root and leaf growth.

Plants that I like to divide in the spring include asters (Aster spp.), penstemon (Penstemon), blanket flower (Gaillardia), and columbine (Aquilegia spp.). While my columbines start blooming in summer, I’ve found they don’t suffer from spring disturbance.  A key to transplanting columbines involves making sure to dig deeply to get all the tapering, finger-like roots.  Divide the roots with a sharp knife. 

While daylilies (Hererocallisis spp.) may not look root bound, dividing every 3-5 years promotes a heavier bloom. UME suggests dividing delphinium (Delphinium grandiflorum) in the spring as plants dug in fall often die over the winter.  I find if I divide them every 3 or so years they tend to last longer.  When I didn’t divide them they tended to die about after a few years.

Iris (Iris) can be divided in either spring (when leaves are only 3 – 4 inches tall) or in early fall when there is still time for the roots to get established.  I usually wait until fall unless I observe a clump that seems too large and is perhaps coming up out of the soil.

Tall phlox (Phlox paniculata) can be divided in the spring.  Take a close look at the central core and discard it if it’s dead or woody.  Shasta daisies (Leucanthemum x superbum) tend to die out if not divided every 3 or so years.  The clump may not look root bound, but if you notice you’re getting fewer blooms, it’s time to divide.

Snow-in-summer (Aegopodium podagraria) recovers quickly from transplanting so can be divided almost any time. I have a couple of areas in my yard that I’ve let it take over.  After a few years it doesn’t look as healthy if I don’t thin it out.

I’m looking forward to getting out in the garden – especially on days that aren’t windy!  If transplanting it’s a good idea to pick a cloudy day or early morning.  Disturbing plants in the heat of the day can make it much harder for them to recover.

“In spring, at the end of the day, you should smell like dirt.” Margaret Atwood