Perennials: Some you cut down, some you leave standing

It’s just about that time of year when gardeners begin to question their gardening choices about perennials: what do I leave over the winter and what do I cut down now? It seems to me that we need some sort of guideline; something to help you make intelligent garden decisions so you can say definitively, “THIS is getting its head cut off and this one will stand for the winter.”  

So here it is, the best simple guide I could come up with:

Leave it standing if:

- It has matured seed heads as birds will forage on the seeds throughout the winter

- It has a rigid stem that is unlikely to be blown over by blustery winter winds

- It is an ornamental grass (Calamagrostis, Miscanthus, etc.)

Cut it back now if:

- The foliage is floppy, yellow or black, and looks unattractive in your fall garden - peonies, daylilies, hostas etc. (throwing everything into the composter, of course)

- You don’t like the look of it - remember, it’s your garden

- The seed heads have been ravaged by the birds and there are no seeds left (Echinacea, most likely)

Echinacea

In my garden, I tend to follow these ‘rules’ but I also tend to make on-the-spot decisions based solely on the situation. This past weekend, I cut back all of the Shasta Daisies (to about 5 centimeters). Shastas tend to turn yellow or brown and get a bit slimy after the first few frosts and I find it easier to clean them up before it gets to this point.

Some of my blue Veronica have been cut back and some have not - there’s a reason for that. The Veronica that was cut back had been overtaken by a rogue clematis and I wanted to comb it out before winter. The clematis will come back and in a few years will need another trimming but for next spring, the Veronica will have a little more room to grow. The rest of the Veronica have been left as the seed heads will make a few overwintering birds a little less hungry.

Truth is, there is no harm in cutting herbaceous perennials back to the ground or leaving them standing. Most of it, for me, is a personal preference: I like some left upright for the winter to add a little winter interest to the otherwise dreary winter garden. Mounds of snow will form on top of the Echinacea seed heads and within the nooks and crannies of the tall grasses.

Yes, eventually, if we get enough snow, many of the stalks will be buried within the white clutches of winter’s wrath. Until then, I’ll be glad to enjoy the contrast brought about by the remaining stems nestled within the snow.

Mark Cullen is an expert gardener, author and broadcaster. Get his free monthly newsletter at markcullen.com. Look for his new best seller, The New Canadian Garden' published by Dundurn Press. Follow him on Twitter @MarkCullen4 and Facebook.