Preparing a perennial garden for winter at 49° North


Attention perennial gardeners, fall is the time to … Get a “Move On”

The great divide or investing in strong stock

If there was ever a time to rest on your laurels as a gardener its August and the beginning of September – unless of course frost warnings have you scrambling hither and yon collecting produce and protecting tender plants. However as September comes to a close the perennial garden needs a critical examination.  This is an opportune time to move or divide perennials. But there are rules to adhere to and certain protocols to follow in order to meet success for the spring. As a general rule of thumb, if a plant blooms between early spring and late June, an early division is ideal. If a plant blooms after late June – then early spring division is best. There are some perennials which require special attention, for example Peonies should only be moved/divided in the fall, Oriental Poppies should be moved/divided in August, Bearded Iris and Lilies should be moved/divided in mid to late fall. However one can always bend the rules and I do all the time. If you don’t push the boundaries you will never reap the rewards.  An autumn stratagem such as this accelerates the burgeoning appeal of your perennial beds so shake the cobwebs out and make September and October your time to get a head start on renovating your perennial beds.

Come August I tend to take a scrutinizing gander over the entire garden. With a critical eye I evaluate the if everything met my expectations.  I also track what I loved most in my garden journal; make wish lists for new acquisitions, as well as take account of what some of my kindred gardener’s successes were. Photos aptly illustrate my true loves. They also show the commonplace or noxious dwellers that beg to be shifted or banished.

I celebrate my successes and learn from my failures (or neglect). I also remember what I merely tolerated. The best part of photography is that it is a nice way to record the evolution of one’s yard as the years pass. Photos (digital photos at this juncture) help me to find where I relegated my new perennials in the autumn. This is a preventive measure as well as an artistic maneuver on my part, as it prevents me from inadvertently tearing or hoeing out, a fall edition in the perennial bed come May or June. This is my why not cutting back my perennials in autumn. I like most of the foliage to stay on the plant so that I know the lay of the land come spring. If there is insufficient foliage I recommend placing a good-sized marker or small stake and if no foliage is present a tag or wooden stick with the name of the plant. Besides that, leaving perennials intact adds visual and auditory interest in the winter, (ie. Ornamental grasses, Astilbe, Echinacea, Joe Pye weed, Virginia creeper), traps snow for better snow coverage (mulch) and provides for protective and secure perches for small birds in the winter.

Some perennials carry over the winter in a low clump of evergreen leaves near the ground, known as a “rosette”. Although you can trim the upright stems back on these “rosettes”, leaving the lower leaves intact. Remove only the brown or obvious dead parts of these plants in the spring. Some examples of “rosette” perennials are: Coreopsis, Digitalis, Gaillardia, Heuchera, Bearded Iris, Shasta Daisies, Penstemon, Poppies, Polemonium, Salvia, Primula, and Tiarella.

I keep an eye on the super-size perennials during the course of the summer so that when fall draws nigh, I have secured them some new real estate. This sometimes requires careful consideration and sometimes overall refurbishing of perennial beds in order to accommodate several specimens. You will find that some years you have many, many changes to make however I assure you, your hard work in September and October will be thoroughly rewarding in the spring. Sometimes a wet fall makes it more difficult to get into the garden. A dry fall is serendipity for a gardener so take advantage of what nature provides. When spring finally sashays into Manitoba, the results of your hard work will be a sensation. The newly refurbished perennial bed unfurls transformed for everyone to enjoy and admire.

There’s an army of reasons to move any given perennial. You may do so because it was in the wrong site. It may have been overshadowed by a shrub or scorched by the sun and is crying out for more shade or diffused light or the reverse may hold true, perhaps the drainage was poor, or it might merely need dividing after its fourth year ~ whatever the reason you must dig the entire plant up. Assess if it requires dividing and check the condition of the plant at large. It can be cut into halves or thirds using two shovels. I find a gardening knife an ideal way to saw through thick roots. If you don’t have room for the remaining part of the plant offer it to a neighbour or a friend, perhaps a trade will occur. Isn’t this what perennial gardening is all about… plenitude and sharing?

Dig the hole 5 to 10 inches deeper than the root ball, depending on the size of the perennial. Amend the soil by adding some compost (or Sea Soil), worm-castings or coco earth (if the soil is compacted with clay) or throw in combination thereof. Place the plant into the hole. Fill with remaining soil. Remove excessive foliage to promote root growth and serious wilting, which is desirable in the fall as plants are going into dormancy. Water in with Sea Magic as it is beneficial for stronger and speedier root development.

You must never, never fertilize in autumn. You may fertilize again in the spring once you see signs of leaf development. (Fertilizing a dormant perennial will encourage it to set out new growth, which will compromise it overwintering to its fullest potential.) Water the transplant regularly until the ground freezes being careful not to drown the roots through over-watering. Sometimes rainfall will not adequately “water in” the new transplant so check regularly until the ground freezes or snow falls, whichever comes first.

If you are choosing a new perennial from a garden centre, choose strong, healthy specimens. The foliage may not be impeccable this time of year but do check for disease or pests.  Look for over-sized perennials as they will give back forcefully and will require less monitoring than a minuscule plant. (Small perennials are best purchased in the spring when you can check its development more carefully). This might be just the time to choose something unusual or even reach into a less hardy Zone especially if you are providing winter protection.

This article was written for a workshop I gave at Sage Garden on September 28, 2011

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