[GPI]

How to prune your perennials when they look a bit tired.
by GPI

To cut back or not to cut back, that’s a question a lot of gardeners who grow perennials will be asking themselves over the next month or so. The spring flowering perennials (e.g. Columbine, candytuft etc.) and the early summer flowering varieties (e.g. foxglove, Geum etc.) can indeed look a bit tired, battered and lanky around this time of the year, making them prime candidates for a remedial tidy-up.

So this is pruning after flowering to improve the look of the garden, removing the dead looking plant growth, which has been weather-beaten by wind, rain and occasional sun. Along with the aesthetic improvement that cutting back brings, it also protects recently planted perennials from damage by the higher winds which tend to arrive as we enter autumn. A tall un-topped perennial catching the wind like a sail could possibly be damaged by wind-rock, breaking the plants roots which slows the uptake of water/food, thus reducing plant vigour.

I have compiled a few rules and tips that you should keep in mind when you get around to grooming your own perennials…

Perennial tissue is either fleshy or soft wood so you will get by with just two pruning tools in your arsenal, the secateurs for clean cut through woody stems and the old fashioned hedge clippers for pruning several soft stems in one go. Ensure that the secateurs or hand pruners is the by-pass variety so that it can make a clean cut through the stem of the plant, rather than crush it like the anvil type pruners can. Don’t worry if you don’t know which is which as your local garden centre helpers will be able to show you the difference.

. Monarda also known as beebalm, its seed heads may be best left unpruned, photo / picture / image.

If your aim is to force the perennial to produce fresh new foliage to make the plant look more attractive, then cutting the brown woody parts of the plant to ground level will stimulate this type of growth. Along with the fresh growth you may receive a second flush of flowers as a bonus, or you may not, depending on how late in the season it is and what the plants remaining food reserves are like. Your cuts should be made to just above new basal foliage/buds or one to two inches above ground to prevent the accidental removal of newly popped buds.

Another way to freshen up your perennials is to cut them back by one-half; this again promotes some fresh growth to liven things up. It is also serves the dual purpose of making a bit of room without leaving a hole, keeping the perennial plants from invading the space of others in the oft overpopulated garden of the plant lover.

Many perennials don’t need to be cut back hard at all; instead selective leaf removal may be all that is necessary. Lady’s Mantle, Heuchera and Berginia (elephants ears) are all plants that need occasional leaf removal due to sun scorch, where the leaves become crinkly or where a touch of leaf spot is ruining the overall look. Another advantage of leaving the majority of foliage intact on these low growing leafy specimens is the protection it offers their buds and roots during a winter of harsh frosts.

Then there are the perennial you should leave unpruned just so that your garden birds can feast on their seed heads. Examples of these protein and oil-rich food sources for birds include Echinacea the cone flower, Eryngium the sea holly, beebalm, Rudbeckia, Coreopsis, Scabiosa, and not forgetting Liatris spicata known as gayfeather.

An added benefit to these seed heads are the form and texture they add to the winter landscape. Leaving such seed heads on the plant will allow you to enjoy their striking winter effect as they are enhanced by a covering of snow or frost. One perennial in particular, Sedum ‘Autumn Joy’ has seed heads resembling flat caps, which are renowned for their magical winter appeal.

As with many things in the garden “less is more” so it may be worth your while to take it a little easy on your perennial clean up.

Any queries or comments on How to prune your perennials when they look a bit tired, please post below.
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[Sive]

I grew foxgloves from seed last year, and cut some of them right down when they had finished flowering this summer....I'm amazed to see a second flush of (much shorter) flowers appearing now. I didn't realise that could happen with biennials.

[Dr. Sunny Thomson]

If they had not had the chance to spread their seed before being cut down they will often force another set of flowers to get to the seed spreading stage.
Nature doesn't give up that easy.